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Magnetic Anisotropy (magnetic + anisotropy)
Kinds of Magnetic Anisotropy Selected AbstractsArrays of Electroplated Multilayered Co/Cu Nanowires with Controlled Magnetic AnisotropyADVANCED ENGINEERING MATERIALS, Issue 12 2005R. Pirota The controlled production of arrays of nanowires exhibiting outstanding characteristics is recently attracting much interest owing to their applications in a number of emerging technologies related with multifunctional biosensor applications, controlled optomagnetic response, magnetic storage, magnetotransport, or catalytic performance. While nanolitography methodes require sophisticated experimental facilities, an alternative technique that makes use of much simpler conventional anodization and electrodeposition methods in the fabrication of metallic nanowires arrays is increasingly employed. This method allows the preparation of arrays of highly-ordered nanopores induced by anodisation, and its filling with metallic elements by electrodepositon. [source] Ionothermal Synthesis of Extra-Large-Pore Open-Framework Nickel Phosphite 5,H3O,[Ni8(HPO3)9Cl3],1.5,H2O: Magnetic Anisotropy of the Antiferromagnetism,ANGEWANDTE CHEMIE, Issue 13 2010Hongzhu Xing Mikroporöse Magnete: Die Struktur der Titelverbindung (siehe Einschub) weist zweidimensionale Nickel-Sauerstoff/Chlorid-18-Ring-Schichten auf, die entlang der c -Achse gestapelt und durch HPO3 -Einheiten verknüpft sind. Nach Messungen der magnetischen Anisotropie an ausgerichteten Einkristallen (siehe Graph) ist die leichte magnetische Achse senkrecht zur Schichtebene. [source] How to Build Molecules with Large Magnetic AnisotropyCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2009Jordi Cirera Dr. Abstract Predicting single-molecule magnets? Magnetic anisotropy, a property that plays a key role in single-molecule magnets (SMMs), has been analyzed by using theoretical methods. Mononuclear complexes and the dependence of the magnetic anisotropy on their geometrical and electronic structure, as well as how such mononuclear complexes must be combined as building blocks to obtain polynuclear complexes with large anisotropy (see figure) are considered. The magnetic anisotropy of mononuclear transition-metal complexes has been studied by means of electronic structure calculations based on density functional theory. The variation of the zero-field splitting (ZFS) parameters has been analyzed for the following characteristic distortions: a tetragonal Jahn,Teller distortion, the Bailar twist, the Berry pseudorotation, and the planarization of tetrahedral complexes. Finally, the coupling of mononuclear building blocks in polynuclear complexes to obtain a large negative magnetic anisotropy necessary to improve their single-molecule-magnet (SMM) behavior has been studied. [source] The influence of substrate on the magnetic properties of MnZn ferrite thin film fabricated by alternate sputteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008Lanxi Wang Abstract Mn0.5Zn0.5Fe2O4 film which has the highest saturation magnetization among Mn1,xZnx Fe2O4 thin films was prepared by the alternate rf sputtering method from two targets with compositions of MnFe2O4 and ZnFe2O4, respectively. The films were deposited on single-crystal Si(100), MgO(100) and SiO2/Si(100) substrates. The as-deposited films were amorphous, and after annealing in a vacuum furnace at 550 °C, polycrystalline MnZn ferrite films with residual amorphous matrix were obtained. The coercivity of all films is low, and the film on the MgO(100) substrate shows a coercivity as low as 27 Oe. The grain size of all films is about 20 nm and is less than the ferromagnetic exchange length (160 nm), so magnetic anisotropies are averaged to lower effective values. Furthermore, the negative magnetostriction constant of crystalline MnZn ferrite and the positive magnetostriction constant of amorphous Fe-based matrix will cancel out and may lead to a low or vanishing saturation magnetostriction constant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] FMR study of strain-induced magnetic anisotropies in CrO2 thin filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004B. Z. Rameev Abstract Epitaxial CrO2 thin films were grown on TiO2 (100) single-crystalline substrates by chemical vapour deposition (CVD) process with use of CrO3 solid precursor. The films with different thickness (27,530 nm) were studied by Ferromagnetic Resonance (FMR) technique. Strong dependence of FMR signal on the film thickness was observed in the series of CrO2 films deposited onto the pre-etched TiO2 substrates. It is shown that the magnetic behaviour of the CrO2 films arises from competition between magnetocrystalline and strain anisotropies that favour the [001] and [010] magnetization directions, respectively. For the thinnest film the strain anisotropy dominates, and the magnetic easy axis switches from [001] to the [010] direction. On the contrary, the CrO2 film grown on the unetched substrate demonstrates essentially strain-free magnetic anisotropy behaviour. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modelling of magneto-mechanical hysteresis loops in Ni-Mn-Ga shape memory alloysPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004Laurent HirsingerArticle first published online: 17 DEC 200 Abstract A predictive model of field-induced strain in Ni-Mn-Ga ferromagnetic shape memory alloys is proposed. In this study, magnetocrystalline anisotropy K1 is introduced to permit magnetisation rotation in martensite platelets. The demagnetisation field induced by the shape of platelets is investigated. The proposed model is identified on experiments performed by Straka et al. This identification shows that observed macroscopic hysteresis loops, i.e. magnetisation and detwinning strain versus applied magnetic field, correspond exactly to a successive activation of three mechanisms: Movement of 180° domain walls, rotation of magnetisation and martensite detwinning. As expected, magnetization and strain -induced by magnetic field- in a single crystal are mainly given by the mobility of twin boundaries and magnetic anisotropies (due to the martensite crystallographic structure and to the shape of platelets). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects?CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010Characterization, Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear FeIII Triplesalen Complexes, Synthesis Abstract The chiral triplesalen ligand H6chand provides three chiral salen ligand compartments in a meta -phenylene arrangement by a phloroglucinol backbone. The two diastereomeric versions H6chandRR and H6chandrac have been used to synthesize the enantiomerically pure chiral complex [(FeCl)3(chandRR)] (3RR) and the racemic complex [(FeCl)3(chandrac)] (3rac). The molecular structure of the free ligand H6chandrac exhibits at the terminal donor sides the O-protonated phenol,imine tautomer and at the central donor sides the N-protonated keto,enamine tautomer. The trinuclear complexes are comprised of five-coordinate square-pyramidal FeIII ions with a chloride at the axial positions. The crystal structure of 3rac exhibits collinear chiral channels of ,11,Å in diameter making up 33.6,% of the volume of the crystals, whereas the crystal structure of 3RR exhibits voids of 560,Å3. Mössbauer spectroscopy demonstrates the presence of FeIII high-spin ions. UV/Vis spectroscopy is in accordance with a large delocalized system in the central backbone evidenced by strong low-energy shifts of the imine ,,,* transitions relative to that of the terminal units. Magnetic measurements reveal weak intramolecular exchange interactions but strong magnetic anisotropies of the FeIII ions. Complexes 3rac and 3RR are good catalysts for the sulfoxidation of sulfides providing very good yields and high selectivities with 3RR being enantioselective. A comparison of 3RR and [FeCl(salen,)] provides higher yields and selectivities but lower enantiomeric excess values (ee values) for 3RR relative to [FeCl(salen,)]. The low ee values of 3RR appeared to be connected to a strong ligand folding in 3RR, opening access to the catalytically active high-valent Fe,O species. The higher selectivity is assigned to a cooperative stabilization of the catalytically active high-valent Fe,O species through the phloroglucinol backbone in the trinuclear complexes. [source] Shape and Magnetic Properties of Single-Crystalline Hematite (,-Fe2O3) NanocrystalsCHEMPHYSCHEM, Issue 9 2006Huaqiang Cao Prof. Unusual magnetic behavior of ,-Fe2O3: Rice- (a) and cube-shaped (b) single-crystalline ,-Fe2O3 nanostructures (see microstructure images) are obtained by a new hydrothermal reaction route. Different magnetic anisotropies are observed for the rice- and cube-shaped ,-Fe2O3 nanocrystals. This behavior offers possibilities for technological applications of ,-Fe2O3 with magnetic properties tailored by shape-controlled synthesis. [source] A Haigh,Mallion-Based Approach for the Evaluation of the Intensity Factors of Aromatic RingsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2006Cristiano Zonta Abstract A novel method for the determination of intensity factors of benzenoid systems based on the Haigh,Mallion (HM) theory has been developed. In this paper, the magnetic anisotropy generated by the ring-current effect in polycondensed arenes has been quantitatively calculated as nuclear independent chemical shieldings (NICSs) in a three-dimensional grid of points using the B3LYP/6-31G(d) method implemented in the Gaussian 98 program. The fitting of the calculated values to the HM model gives intensity factors for each ring. A comparison of the obtained values with Schleyer's NICS0 is given. The obtained intensity factors may find application in software using 1H NMR chemical shifts for structure determination.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Diffusion in Nanocrystalline Metals and Alloys,A Status Report,ADVANCED ENGINEERING MATERIALS, Issue 5 2003R. Würschum Abstract Diffusion is a key property determining the suitability of nanocrystalline materials for use in numerous applications, and it is crucial to the assessment of the extent to which the interfaces in nanocrystalline samples differ from conventional grain boundaries. The present article offers an overview of diffusion in nanocrystalline metals and alloys. Emphasis is placed on the interfacial characteristics that affect diffusion in nanocrystalline materials, such as structural relaxation, grain growth, porosity, and the specific type of interface. In addition, the influence of intergranular amorphous phases and intergranular melting on diffusion is addressed, and the atomistic simulation of GB structures and diffusion is briefly summarized. On the basis of the available diffusion data, the diffusion-mediated processes of deformation and induced magnetic anisotropy are discussed. [source] Spontaneous Outcropping of Self-Assembled Insulating Nanodots in Solution-Derived Metallic Ferromagnetic La0.7Sr0.3MnO3 FilmsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009César Moreno Abstract A new mechanism is proposed for the generation of self-assembled nanodots at the surface of a film based on spontaneous outcropping of the secondary phase of a nanocomposite epitaxial film. Epitaxial self-assembled Sr,La oxide insulating nanodots are formed through this mechanism at the surface of an epitaxial metallic ferromagnetic La0.7Sr0.3MnO3 (LSMO) film grown on SrTiO3 from chemical solutions. TEM analysis reveals that, underneath the La,Sr oxide (LSO) nanodots, the film switches from the compressive out-of-plane stress component to a tensile one. It is shown that the size and concentration of the nanodots can be tuned by means of growth kinetics and through modification of the La excess in the precursor chemical solution. The driving force for the nanodot formation can be attributed to a cooperative effect involving the minimization of the elastic strain energy and a thermodynamic instability of the LSMO phase against the formation of a Ruddelsden,Popper phase Sr3Mn4O7 embedded in the film, and LSO surface nanodots. The mechanism can be described as a generalization of the classical Stranski,Krastanov growth mode involving phase separation. LSO islands induce an isotropic strain to the LSMO film underneath the island which decreases the magnetoelastic contribution to the magnetic anisotropy. [source] Concentric Sub-micrometer-Sized Cables Composed of Ni Nanowires and Sub-micrometer-Sized Fullerene Tubes,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2007F. Tao Abstract Highly ordered arrays of submicrometer-sized coaxial cables composed of submicrometer-sized C60 and C70 tubes filled with Ni nanowires are successfully prepared by combining a sol,gel method with an electrodeposition process. The wall thickness of the submicrometer-sized tubes can be adjusted by the concentration of fullerenes and the immersion time. The thermal stability of the submicrometer-sized C60 tubes is studied by Raman spectroscopy and it is found that these structures can be easily decomposed to form carbon nanotubes at relatively low temperatures (above 573,K) in an alumina template. These novel coaxial cable structures have been characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), field-emission SEM (FESEM), Raman spectroscopy, elemental mapping, energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) experiments, and superconducting quantum interference device (SQUID) measurements. Magnetic measurements show that these submicrometer-sized cables exhibit enhanced ferromagnetic behavior as compared to bulk nickel. Moreover, submicrometer-sized C70/Ni cables show uniaxial magnetic anisotropy with the easy magnetic axis being parallel to the long axis of the Ni nanowires. C70/Ni cables also exhibit a new magnetic transition at ca.,10,K in the magnetization,temperature (M,T) curve, which is not observed for the analogous C60/Ni structures. The origin of this transition is not yet clear, but might be related to interactions between the Ni nanowires and C70 molecules. There is no preferred magnetization axis in submicrometer-sized C60/Ni cables, which implies that the Ni nanocrystals have different packing modes in the two composites. These different crystalline packing modes lead to different magnetic anisotropy in the two composites, although the Ni nanocrystals have the same face-centered cubic (fcc) structure in both cases. [source] Design of the Magnetic Properties of Fe-Rich, Glass-Coated Microwires for Technical Applications,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2006A. Zhukov Abstract The magnetic anisotropy of Fe-rich, thin, amorphous wires is tailored by stress annealing (SA). In particular, the effect of conventional annealing (CA) and SA on the magnetic properties of Fe74B13Si11C2 glass-coated microwires is studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain SA conditions (annealing temperature, Tann,>,300,°C; applied stress, ,,>,400,MPa), a transverse magnetic anisotropy is induced: a rectangular hysteresis loop transforms into an inclined one at magnetic-anisotropy fields above 1000,A,m,1. Under tensile stress, the rectangular hysteresis loop of microwires annealed using SA is recovered. Samples subjected to SA show noticeable magnetoimpedance and stress-impedance effects, despite their large magnetostriction. The samples obtained exhibit a high stress sensitivity of their giant magnetoimpedance (GMI) effect and hysteretic properties, allowing the use of the obtained samples in magnetoelastic sensors, and for designing stress-sensitive, tunable composite materials. By varying the time and temperature of such SA, we are able to tailor both the magnetic properties and the GMI of Fe-rich microwires. [source] Microfluidic Assembly of Magnetic Hydrogel Particles with Uniformly Anisotropic StructureADVANCED MATERIALS, Issue 31 2009Chia-Hung Chen Monodisperse magnetic particles are templated from double emulsions formed using sequential flow-focus drop formation. The microfluidic drop formation allows the particles to be formed with high monodispersity and with consistently anisotropic internal structure. This structural anisotropy gives rise to magnetic anisotropy, allowing the particles to be rotated by a magnetic field. [source] 1H chemical shifts in NMR: Part 22,,Prediction of the 1H chemical shifts of alcohols, diols and inositols in solution, a conformational and solvation investigationMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2005Raymond J. Abraham Abstract The 1H NMR spectra of a number of alcohols, diols and inositols are reported and assigned in CDCl3, D2O and DMSO- d6 (henceforth DMSO) solutions. These data were used to investigate the effects of the OH group on the 1H chemical shifts in these molecules and also the effect of changing the solvent. Inspection of the 1H chemical shifts of those alcohols which were soluble in both CDCl3 and D2O shows that there is no difference in the chemical shifts in the two solvents, provided that the molecules exist in the same conformation in the two solvents. In contrast, DMSO gives rise to significant and specific solvation shifts. The 1H chemical shifts of these compounds in the three solvents were analysed using the CHARGE model. This model incorporates the electric field, magnetic anisotropy and steric effects of the functional group for long-range protons together with functions for the calculation of the two- and three-bond effects. The long-range effect of the OH group was quantitatively explained without the inclusion of either the CO bond anisotropy or the COH electric field. Differential , and , effects for the 1,2-diol group needed to be included to obtain accurate chemical shift predictions. For DMSO solution the differential solvent shifts were calculated in CHARGE on the basis of a similar model, incorporating two-bond, three-bond and long-range effects. The analyses of the 1H spectra of the inositols and their derivatives in D2O and DMSO solution also gave the ring 1H,1H coupling constants and for DMSO solution the CHOH couplings and OH chemical shifts. The 1H,1H coupling constants were calculated in the CHARGE program by an extension of the cos2, equation to include the orientation effects of electronegative atoms and the CHOH couplings by a simple cos2, equation. Comparison of the observed and calculated couplings confirmed the proposed conformations of myo -inositol, chiro -inositol, quebrachitol and allo -inositol. The OH chemical shifts were also calculated in the CHARGE program. Comparison of the observed and calculated OH chemical shifts and CH. OH couplings suggested the existence of intramolecular hydrogen bonding in a myo -inositol derivative. Copyright © 2005 John Wiley & Sons, Ltd. [source] 1H chemical shifts in NMR.MAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2005Part 2, Prediction of the 1H chemical shifts of molecules containing the ester group: a modelling, ab initio investigation Abstract The 1H NMR spectra of 24 compounds containing the ester group are given and assigned. These data were used to investigate the effect of the ester group on the 1H chemical shifts in these molecules. These effects were analysed using the CHARGE model, which incorporates the electric field, magnetic anisotropy and steric effects of the functional group for long-range protons together with functions for the calculation of the two- and three-bond effects. The effect of the ester electric field was given by considering the partial atomic charges on the three atoms of the ester group. The anisotropy of the carbonyl group was reproduced with an asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond with values of ,,parl and ,,perp of 10.1 × 10,30 and ,17.1 × 10,30 cm3 molecule,1. An aromatic ring current (=0.3 times the benzene ring current) was found to be necessary for pyrone but none for maleic anhydride. This result was confirmed by GIAO calculations. The observed 1H chemical shifts in the above compounds were compared with those calculated by CHARGE and the ab initio GIAO method (B3LYP/6,31G**). For the 24 compounds investigated with 150 1H chemical shifts spanning a range of ca 10 ppm, the CHARGE model gave an excellent r.m.s. error (obs , calc) of <0.1 ppm. The GIAO calculations gave a very reasonable r.m.s. error of ca 0.2 ppm although larger deviations of ca 0.5 ppm were observed for protons near to the electronegative atoms. The accurate predictions of the 1H chemical shifts given by the CHARGE model were used in the conformational analysis of the vinyl esters methyl acrylate and methyl crotonate. An illustration of the use of the CHARGE model in the prediction of the 1H spectrum of a complex organic molecule (benzochromen-6-one) is also given. Copyright © 2004 John Wiley & Sons, Ltd. [source] Porous silicon/metal nanocomposite with tailored magnetic propertiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009Petra Granitzer Abstract Porous silicon (PS) templates in the meso/macro porous regime with oriented pores clearly separated from each other and filled in a galvanic deposition process with various metals, especially ferromagnetic ones are magnetically investigated. The employment of different metals (e.g. Ni, Co, NiCo) together with the variation of the electrochemical deposition parameters modifies the structural characteristics of the PS/metal nanocomposite and thus leads to distinct magnetic properties of the hybrid system. Furthermore the use of different PS-templates which means a change of the pore-diameter and interpore spacing results also in various magnetic characteristics, especially influences on the magnetic interactions among the deposited metal nanostructures. Therefore the specimens show tailored magnetic properties like coercivity, squareness and magnetic anisotropy. The achieved nanocomposite merges electronic properties of a semiconductor with nanomagnetism and therefore opens the possibility of integrated spin-based electronic devices. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetoimpedance (MI) in amorphous wires: new materials and applicationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009Larissa V. Panina Abstract The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for applications in smart sensory systems (self-sensing composites) operating at microwave frequencies owing to still very large MI ratios of 50,100% in Co-rich amorphous wires at GHz frequencies. Here we introduce two types of MI wire composites: 2D-arrays and mixtures of wire pieces. In such materials the effective permittivity has strong dispersion in a frequency band determined by a plasma frequency or a dipole resonance, respectively. If MI wires are used as constituent elements, this dispersion may be very sensitive to the magnetic properties of wires since the wire impedance determines the relaxation parameter of the effective permittivity. For example, increasing the wire impedance by establishing the magnetisation along the axis with an external magnetic field broadens the resonance band, decreases the reflection amplitude and may open a bandpass. Depending on the magnetic anisotropy in wires, tuning can be realized with both magnetic field and stress. It is foreseen that MI-wire composite materials could be suitable for large scale applications, in particular, for free space filters in secure wireless systems and for microwave nondestructive testing and control in civil engineering. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Linear and nonlinear magneto-optical response of ultrathin Co/Au/Mo and Co/Mo films grown on sapphire substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008A. Stupakiewicz Abstract We report studies of the linear and nonlinear magneto-optical properties of epitaxial ultrathin Co films grown on sapphire substrates covered with Mo or Mo/Au buffers. Changes of the crystallographic symmetry and magnetization of buried interfaces were deduced from the magneto-optical Kerr effect hysteresis loops and magnetization-induced second-harmonic generation (MSHG). Depending on the buffer, two-fold (for Mo buffer) or six-fold (for Mo/Au buffer) symmetries were observed in both inplane magnetic anisotropy and MSHG intensity. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ferromagnetic nanoparticles embedded in self-arranged matricesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008K. Rumpf Abstract The investigated nanoscopic system, consisting of a non magnetic host material and precipitated ferromagnetic nanostructures shows a magnetic behaviour correlated to the size and shape of the deposited particles but also to their spatial distribution within the template which modifies the magnetic interactions between them. The nanostructures are deposited electrochemically into an etched silicon wafer exhibiting an array of channels of a few ten nanometers in diameter and a length up to 50 µm. The self-assembled grown templates offer the opportunity of tuning the magnetic properties by varying the geometrical characteristics of the membrane which can be loaded with different metals like Ni or Co with variable metal distribution. Magnetic characteristics like coercivity, magnetic anisotropy and temperature dependent magnetization give a survey about the structure and the magnetic interactions of the nanocomposite. This achieved ferromagnetic nanocomposite system is not only of interest for basic research but also gives rise to applications in magneto-optics, spintronics and sensor application. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bulk anisotropy Nd-Fe-B/,-Fe nanocomposite permanent magnets prepared by sonochemistry and spark plasma sinteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Peili Niu Abstract NdFeB/,-Fe nanocomposite magnetic powders were prepared by sonochemical process. The powders were then submitted to a hot press and subsequent hot deformation process by spark plasma sintering (SPS) technique. Effect of ,-Fe content on structure and magnetic properties of both isotropic and anisotropic magnets was investigated. For hot pressed magnets, the remanence increases with the content of ,-Fe, while the coercive force drops simultaneously. After hot deformation, the magnets with no more than 2 vol% ,-Fe exhibit obvious anisotropic characteristic. For the magnets with more ,-Fe, however, the magnetic anisotropy disappears due to the absence of (00l) crystal texture after deformation. It is, therefore, expected that ,-Fe content plays an important role in the formation of C-axis crystal texture during hot deformation process. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Longitudinal and transverse incremental permeability of Co19.35Fe53.28Hf7.92O19.35 filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Anh-Tuan Le Abstract We present here, the results of a thorough study of the longitudinal permeability ratio (LPR) and transverse permeability ratio (TPR) in sputtered Co19.35Fe53.28Hf7.92O19.35 films with varying thicknesses (t = 1, 1.5, 1.8 and 2.4 µm) in the frequency range of 100 - 1000 MHz. It is found that for all samples investigated, the LPR/TPR first increases with increasing frequency, reaches a maximum at 710 MHz, and then decreases at higher frequencies. This is related to the ferromagnetic resonance. The LPR and TPR profiles measured along the easy axis of the film show a single-peak feature, whereas those measured along the hard axis of the film show a double-peak one. This indicates an existence of magnetic anisotropy and its dispersion in the films. It reveals that the study of LPR and TPR spectra provides an alternative way for the evaluation of the high-frequency magnetic softness of film-type materials. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The property of multilayered SmCo5 film with perpendicular magnetic anisotropyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Shigeto Takei Abstract In order to fabricate thick SmCo5 film, the dependences of the magnetic properties of SmCo/Ru/Cu/Ru films and its multilayer films on the SmCo layer thickness were studied. The SmCo/Ru/Cu/Ru film with the SmCo layer thickness up to 200 nm showed the perpendicular magnetic anisotropy while the multilayer film with the total SmCo layer thickness of 1000 nm indicated the magnetic easy axis was in the perpendicular direction. It was found that the multilayered structure is preferable for the increase in total thickness of the SmCo layer with the perpendicular anisotropy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Soft magnetic properties and microstructure of Fe65Co35 thin films with different underlayersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006Yu Fu Abstract High-moment soft magnetic Fe65Co35 thin films with well in-plane uniaxial anisotropy were obtained by cosputtering on Co93Fe7, Ni80Fe20, Cu and Fe underlayers. The single-layer Fe65Co35 film with thickness of 100 nm shows a magnetic anisotropy. The coercivity along easy axis Hce and that along hard axis Hch are equal to 3.3 kA/m and 2.1 kA/m, respectively. The soft magnetic properties of Fe65Co35 films were much improved by using an underlayer. The Hce and Hch of Fe65Co35 films with Ni80Fe20, Co93Fe7 and Cu underlayers can be reduced to 0.9,1.1 kA/m and 0.08,0.20 kA/m, respectively. For films with Fe underlayer, the Hce and Hch reduced to 1.1 kA/m and 0.6 kA/m, respectively. In the case of Co93Fe7, Ni80Fe20 and Fe underlayers, the coercivity of films did not depend remarkably on the thickness t of underlayer at t > 1 nm. While in the case of Cu underlayer, the coercivity of films changed remarkably with increasing underlayer thickness. It was shown that the texture of double-layered underlayer/Fe65Co35 films is dependent on the material and the thickness of underlayer. The influence of the underlayer on the surface morphology and micro-magnetic structure of films were investigated by AFM and MFM. It was suggested that the modification of the structure of Fe65Co35 films by using an underlayer is an important way to improve their soft magnetic properties. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characteristic magnetic length-scales in Vitroperm , Combining Kerr microscopy and small-angle neutron scatteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004A. Grob Abstract We present a study of the magnetic-field dependence of the magnetic microstructure of the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic magnetic anisotropy. The samples were analysed using Kerr microscopy and small-angle neutron scattering (SANS). As the applied magnetic field is decreased starting from saturation, we find that two processes occur independently: the formation of a domain structure with the net magnetisation of the domains aligned along the macroscopic easy axis and the increase in magnitude of static, nanometer-scale fluctuations of the spin orientation. The domain structure observations from Kerr microscopy are in excellent agreement with the results of the SANS experiments. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth of epitaxial garnet film by LPE for application to integrated magneto-optic light switch arraysPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004J. H. Park Abstract We investigate the dependence of the properties of garnet films grown by liquid phase epitaxy (LPE) on the procedure and the temperature of growth to tailor magnetic properties of Bi, Gd, Ga:YIG film for application to integrated magneto-optic light switch arrays. Because the yttrium and gallium concentrations of the films decreased slightly and the bismuth, iron concentrations of the films increased slightly with decreases of the growth temperature, the magnetic properties of the garnet film grown by LPE are very sensitive specially to a growth temperature. The decrease of Hsat with decreasing growth temperature indicates that the perpendicular magnetic anisotropy energy of the film decreases. The Bi, Gd, Ga:YIG film grown at around 730 °C have good magnetic properties, i.e., a low value of 4,Ms of 120 G, a low value of saturation field Hsat of 168 Oe, and a low perpendicular magnetic anisotropy for application of the magneto-optic spatial light modulators. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetic characterization of U/Co multilayersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003M. A. Rosa Abstract With the aim of expanding the studies on 2D systems containing uranium, U/Co multilayers with layer thickness ranging from 50 to 200 Å were recently prepared by dc magnetron sputtering onto glass. The multilayers were characterized by Grazing-Incidence X-Ray Diffraction (GIXRD) and Rutherford Backscattering Spectrometry (RBS). Magnetization measurements performed with a squid magnetometer showed that the multilayers have a ferromagnetic behaviour, with the magnetic signal increasing with the thickness of the layers. The analysis of magnetic anisotropy evidenced an easy magnetic direction in the film plane with large anisotropy fields, which increase with the thickness of the layers and suggests a positive contribution of surface anisotropy to the effective anisotropy Keff. [source] Domains in helicoidal magnetic structurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2010E. V. Rosenfeld Abstract Theoretical investigation of the magnetic spiral behavior in a layered magnet with strong hexagonal magnetic anisotropy has been performed. It is shown that if the exchange integrals between the first and second neighboring layers meet the requirement |J1|,=,,J2, the energy densities for spirals with three and four (at J1,<,0) or four and six (at J1,>,0) layers in the period coincide. Moreover, near the surface of contact of the above phases the energy density is equal to or even lower than inside each of them, which should result in the appearance of a domain magnetic structure. [source] Magneto-optical spectroscopy of (Zn,Co)O epilayersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2006W. Pacuski Abstract We present a magneto-optical study of (Zn,Co)O layers grown by molecular beam epitaxy. We observed sharp lines related to 4A2,2E intra-ionic Co2+ transitions, and to the A , B and C excitons. Intra-ionic transitions observed by absorption and photoluminescence were used to determine the values of the parameters describing the isolated Co ions, such as the easy-plane magnetic anisotropy and the g -factor of the S = 3/2 Cobalt spin. Excitonic transitions observed in reflectivity were used to determine the giant Zeeman splitting and to estimate the effective coupling ,N0(, , , ),A ,B = 0.4 eV between excitons and Cobalt spins. Due to the electron,hole exchange within the exciton, this effective spin,exciton coupling is much weaker than the exchange integrals for free carriers, estimated to be N0|, , , | , 0.8 eV, with a positive value of (, , , ) if the normal ordering of the valence band of ZnO is assumed. The Zeeman splitting of diluted samples and the magnetic circular dichroism (for a higher Co content) are proportional to the magnetization of the paramagnetic, isolated Cobalt ions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical spin orientation of a single manganese atomPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010C. Le Gall Abstract An optical spin orientation is achieved for a Mn atom localized in a semiconductor quantum dot using quasiresonant excitation at zero magnetic field. Optically created spin polarized carriers generate an energy splitting of the Mn spin and enable magnetic moment orientation controlled by the photon helicity and energy. The dynamics and the magnetic field dependence of the optical pumping mechanism shows that the spin lifetime of an isolated Mn atom at zero magnetic field is controlled by a magnetic anisotropy induced by the built-in strain in the quantum dots. Relaxation times exceeding the micro-second range are measured (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||