Screened real-space Korringa-Kohn-Rostoker description of the relativistic and magnetic properties of transition metals
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The use of the relativistic and spin-polarized real-space Korringa-Kohn-Rostoker (KKR) method is limited to small systems (less than 100 atoms). This is due to the prohibitively large CPU times needed for the inversion of the KKR matrix. To study systems of more than a thousand atoms, we have implemented the concept of a screened reference medium, within the fully relativistic spin-polarized version of the real-space locally self-consistent multiple-scattering method (LSMS). The LSMS method makes use of a local interaction zone (LIZ) for solving the quantum mechanical problem, while the Poisson equation is solved in the whole space. The screened reference medium gives rise to sparse KKR matrices and using state-of-the-art sparse matrix technology a substantial reduction in the CPU times is obtained, enabling applications of the method to systems whose LIZ consists of more than a thousand atoms. The method is benchmarked by application to the elemental transition metals, the fcc (face-centred-cubic) Co and Ni, and the bcc (body-centred cubic) Fe, and compared to the results of the conventional k-space methods. The convergence in real space of the magnetic moments, the magnetocrystalline anisotropy energy and the orbital moment anisotropy is discussed in detail.Keywords:
Magnetocrystalline anisotropy
Relativistic quantum chemistry
Magnetic domain structures of submicrometric epitaxial CrO2 fabricated using selective-area growth technique were studied by magnetic force microscopy. In-plane, lamellar domain structure with fragmented walls aligned along the magnetic easy axis direction is observed, indicating the existence of a large magnetocrystalline anisotropy. A classical model for ferromagnetic materials with a uniaxial anisotropy was used to explain this domain configuration. Estimates of the domain wall energy density and exchange stiffness constant for CrO2 were obtained.
Magnetocrystalline anisotropy
Domain wall (magnetism)
Anisotropy energy
Micromagnetics
Single domain
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Magnetocrystalline anisotropy
Magnetism
Exchange bias
Exchange interaction
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A study is presented of the magnetocrystalline anisotropy of the quasiternary systems (Pr/sub 1-x/Er/sub x/)/sub 2/Fe/sub 14/B and (Pr/sub 1-x/Sm/sub x/)/sub 2/Fe/sub 14/B in which, with increasing x, the easy-magnetization direction changes from easy axis to easy plane. Magnetization measurements on samples aligned magnetically at room temperature have been carried out in fields up to 20 T at temperatures ranging from 4.2 K to room temperature. The data of the easy-axis compounds are analyzed in terms of the anisotropy constants up to sixth-order, taking into account the misalignment of the grains in the magnetically-aligned samples. Special emphasis is given to the influence of the Sm and Er substitutions on the first-order magnetization process and the anisotropy energy of Pr/sub 2/Fe/sub 14/B.< >
Magnetocrystalline anisotropy
Anisotropy energy
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Rare-earth atoms play an important role in determining the magnetocrystalline anisotropy in 4f-3d intermetallic compounds. Recently we reported on the synthesis and magnetic properties of Gd-substituted Mn-Zn ferrite nanoparticles as potentially suitable for magnetic fluid hyperthermia (MFH). In MFH the specific power absorption rate is related to the lossy magnetocrystalline anisotropic properties of the magnetic fluids. In this paper we report the role of Ho substitution in magnetite nanoparticles, which is found to enhance the KV product arising from the large anisotropy of Ho3+ moments. The zero-field-cooled magnetization data is then simulated by assuming noninteracting magnetic particles with uniaxial anisotropy and lognormal particle size distribution. The fit parameters give the values of particle diameter (D) 9 nm, standard deviation 0.3 in ln(D), and the anisotropy constant K to be 3.5×104J∕m3. The value of K thus obtained is an order of magnitude larger than the value known for the undoped for magnetite (104J∕m3).
Magnetocrystalline anisotropy
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Magnetocrystalline anisotropy
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The magnetic anisotropy of pure and Co/Ti-doped Ba ferrite particles is analyzed through the evaluation of the dependence on temperature of the constants of magnetocrystalline and shape anisotropy, which both are present in the platelet-like Ba ferrite particles with hexagonal structure. In undoped Ba ferrite, the magnetocrystalline anisotropy constant is predominant on the conflicting shape anisotropy constant at all temperatures, which indicates that the magnetic anisotropy is uniaxial, with preferred direction for the magnetization along the c axis of the hexagonal particles. In doped particles, where the magnetocrystalline anisotropy is weakened by the ionic substitutions, while at high temperatures the magnetic anisotropy is substantially uniaxial with c as axis of easy magnetization, when the temperature decreases, the shape anisotropy constant becomes larger than the magnetocrystalline anisotropy constant, and consequently, the magnetic anisotropy is not uniaxial, but it presents multiple preferred directions for the magnetization
Magnetocrystalline anisotropy
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Magnetocrystalline anisotropy
Lattice (music)
Anisotropy energy
Crystal (programming language)
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Magnetocrystalline anisotropy
Tetragonal crystal system
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The magnetic anisotropy of 3-nm wide cobalt nanowires embedded in epitaxial CeO 2 /SrTiO 3 (001) layers is investigated by ferromagnetic resonance measurements.The measured magnetic shape and the magnetocrystalline anisotropies confirm that the Co nanowires have their main axes perpendicular to the film surface, and they are composed of hcp Co grains with the c-axes oriented along one of the 〈 〉 111 directions of the CeO 2 matrix.The effects of such a peculiar structure on the magnetic anisotropy are addressed experimentally.The results show that the magnetic anisotropy of the wires is dominated by the magnetostatic term.The inhomogeneous structure of the wires leads to an effective magnetocrystalline anisotropy smaller than the bulk value of hcp Co.
Magnetocrystalline anisotropy
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This paper proposed an improved magnetostriction model for correlation of anisotropy in non-oriented (NO) silicon steel based on the free energy, which considers stress-induced and magnetocrystalline anisotropy. Firstly, the free energy model, which includes stress-induced anisotropy energy, the energy of magnetic field, and the anisotropic energy of magnetic crystals, is incorporated into the anhysteretic magnetization parameter Man. Then, to obtain the magnetic field and proposed model parameters related to stress-induced and magnetocrystalline anisotropy, the magnetostrictive strain loops at different magnetization directions of NO silicon steel are measured. Finally, based on the parameters obtained from experimental data of the proposed model, magnetostrictive strain loops under varying magnetization directions are simulated. This improved magnetostriction model can be applied to the calculation of the vector magnetostriction of the motor core.
Magnetocrystalline anisotropy
Electrical steel
Anisotropy energy
Inverse magnetostrictive effect
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