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Uniaxial Anisotropy (uniaxial + anisotropy)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Anisotropic FMR-linewidth of triple-domain Fe layers on hexagonal GaN(0001)

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
M. Buchmeier
Abstract We present a ferromagnetic resonance (FMR) study of Fe films with thicknesses between 5 and 70 nm prepared by electron-beam evaporation on top of hexagonal GaN(0001). X-ray diffraction (XRD) and low-energy electron diffraction (LEED) suggest the growth in crystallographic Fe(110) domains with three different orientations. The magnetic properties have been investigated by in-plane angle-dependent FMR at frequencies between 4.5 to 24 GHz. All samples show a hexagonal in-plane anisotropy with the easy axes oriented parallel to the Fe [001] directions. The anisotropy field strength of about 8 mT reveals a bulk-like thickness dependence. Therefore, we can exclude the following origins of anisotropy: (i) interface effects because of the bulk-like thickness dependence and (ii) averaged first order cubic or uniaxial anisotropies arising from the three grain orientations because of the relative strengths. We qualitatively explain the sixfold anisotropy by spin relaxation inside the grains. The FMR linewidth versus frequency curves are linear with almost no zero-frequency offset indicating a good homogeneity of the magnetic properties over the sample area. However, the effective damping parameter , shows pronounced anisotropy and thickness dependence, with enhanced damping along the hard axes and for thicker layers. We suggest that the additional damping can be explained by two-magnon scattering at defects which are due to the triple domain structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Soft magnetic properties and microstructure of Fe65Co35 thin films with different underlayers

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2006
Yu 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]

Thermodynamic properties of the Ising and Heisenberg S = 1 ferromagnet with biquadratic exchange and uniaxial anisotropy

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2006
M. Manojlovi
Abstract We study the thermodynamic properties of S = 1 Ising and Heisenberg ferromagnets with both bilinear and biquadratic exchange and/or uniaxial anisotropy of both easy axis/plane character. Using the mean-field (MF) approximation we evaluated the free energy enabling us to study in detail the behavior of the order parameters and the dependence of the critical point on the anisotropy. We show that in the presence of biquadratic interaction, there is a difference in the behavior between the Ising and the Heisenberg model even in the MF approximation, which is not the case for the bilinear interaction. Combining the equations of motion for Green's functions with identities particular to S = 1, we managed to perform the random phase approximation without the decoupling of the operators at the same site, avoiding the peculiarities of the Callen,Anderson decoupling. This allowed us to improve the phase diagram for the Heisenberg model. The important result is the demonstration of the effect of anisotropy to nonvanishing of the quadrupolar order parameter at the Curie point. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Magnetic anisotropy changes in ultrathin Co films grown on vicinal sapphire substrates

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2006
A. Stupakiewicz
Abstract The aim of the work is to study the magnetic anisotropy changes in epitaxial ultrathin Co films grown on vicinal sapphire substrates with different miscut angles. Changes of the in-plane magnetic anisotropy symmetry were deduced from magnetooptical hysteresis loops shape and angular dependence analysis of the resonance field measured in the sample plane. Two-fold and four-fold symmetry of the in-plane anisotropy was observed for different miscut angles. The experimental data are discussed taking into account the following energy contributions: (i) demagnetization; (ii) perpendicular uniaxial anisotropy (iii) and step-induced uniaxial anisotropy. Magnetic anisotropy constants are fitted to the experimental results for different miscut angles. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

On the role of the soft layer in exchange-spring hard/soft magnetic bilayers

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004
D. Bisero
Abstract Bilayers of SmCo/NiFe and SmCo/Co with well-defined in-plane uniaxial anisotropy were grown by dc magnetron sputtering on glass substrates. The magnetization reversal process was investigated by magneto-optic Kerr effect from both sides of the samples, obtaining the hard and soft response separately. The NiFe layers turn out to be exchange coupled to the SmCo films and, for soft layer thicknesses above 30 nm, display reversible demagnetization loops expected from exchange-spring magnets. The experimental NiFe magnetization curve is in good agreement with the theoretical curve obtained by minimizing the magnetic energy in the soft film for an ideal hard/soft bilayer. The soft layer critical thickness above which the exchange spring behavior sets up and its presumed independence on soft layer characteristics are discussed, by comparing the two systems under investigation. We find that SmCo/Co does not fulfil the predictions of the currently accepted theories and that the magnetization reversal of the bilayer is dominated by the Co layer. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]