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Magnetic States (magnetic + states)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Magnonics: Spin Waves on the Nanoscale

ADVANCED MATERIALS, Issue 28 2009
Sebastian Neusser
Abstract Magnetic nanostructures have long been in the focus of intense research in the magnetic storage industry. For data storage the nonvolatility of magnetic states is of utmost relevance. As information technology generates the need for higher and higher data-transfer rates, research efforts have moved to understand magnetization dynamics. Here, spin waves and their particle-like analog, magnons, are increasingly attracting interest. High-quality nanopatterned magnetic media now offer new ways to transmit and process information without moving electrical charges. This new functionality is enabled by spin waves. They are confined by novel functioning principles, which render them especially suitable to operate at the nanoscale. Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light. Combined with nonvolatility, multifunctional metamaterials might be formed. We report recent advances in this rapidly increasing research field called magnonics. [source]

Change in the magnetic properties of [FeII(phen)3](PF6)2 in the solid state by combining grinding and annealing

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004
T. Ohshita
Abstract By grinding crystalline [FeII(phen)3](PF6)2, the effective magnetic moment, or ,MT, increased with simultaneous amorphization. Subsequent annealing further increased ,MT, despite the restoration of the crystallinity. This was explained by the recovery of the counterion, PF6,, from its strained state in the intact crystal to a less strained state towards higher spherical symmetry. The effects of annealing preceded by grinding suggest a novel method to control the magnetic states of coordination compounds without regard to their crystalline states. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Collective magnetic states of ferromagnetic nanoparticles in the superspin limit

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004
S. Bedanta
Abstract Soft ferromagnetic Co80Fe20 nanoparticles embedded discontinuously in [Co80Fe20(tn)/Al2O3]m multilayers are treated as superspins with random size, position and anisotropy. Freezing into collective states rather than single particle blocking is encountered at low temperatures. At low particle density, tn < 1.1 nm, one observes memory and aging of a superspin glass (SSG), while at higher densities, tn > 1.2 nm, superferromagnetic (SFM) domain wall relaxation is, e.g., evidenced by polarized neutron reflectivity. Thermoremanent logarithmic decay rates reveal a universal power law with exponents changing from n < 1 for SSG to n > 1 for SFM in agreement with recent Monte Carlo simulations. At intermediate densities, a crossover occurs from n < 1 with Tln(t/,) scaling at low T to n > 1 as T , Tc. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr7Ni, Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium Cations

CHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009
Angelika
Abstract The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4-DiMe-ImidH][Cr7NiIIF8(O2CtBu)16] 1 (2,4-DiMe-ImidH=the cation of 2,4-dimethylimidazole), [ImidH]2[Cr6NiII2F8(O2CCtBu)16] 2 (ImidH=the cation of imidazole), and [1-Bz-ImidH]2 [Cr7NiII2F9(O2CtBu)18] 3 (1-Bz-ImidH=the cation of 1-benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3. In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X-ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J,,5.8,cm,1, and it is not possible to differentiate the exchange between two CrIII centers (JCrCr) from the exchange between a CrIII and a NiII center (JCrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present. [source]