Multiscale modeling of magnetic materials: Temperature dependence of the exchange stiffness

TY - JOUR

T1 - Multiscale modeling of magnetic materials: Temperature dependence of the exchange stiffness

AU - Atxitia, U.

AU - Hinzke, D.

AU - Chubykalo-Fesenko, O.

AU - Nowak, U.

AU - Kachkachi, H.

AU - Mryasov, O.N.

AU - Evans, R.F.

AU - Chantrell, R.W.

N1 - © 2009 American Physical Society. This is an author produced version of a paper published in PHYSICAL REVIEW B. Uploaded in accordance with the publisher's self archiving policy.

PY - 2010/10/26

Y1 - 2010/10/26

N2 - For finite-temperature micromagnetic simulations the knowledge of the temperature dependence of the exchange stiffness plays a central role. We use two approaches for the calculation of the thermodynamic exchange parameter from spin models: (i) based on the domain-wall energy and (ii) based on the spin-wave dispersion. The corresponding analytical and numerical approaches are introduced and compared. A general theory for the temperature dependence and scaling of the exchange stiffness is developed using the classical spectral density method. The low-temperature exchange stiffness A is found to scale with magnetization as m(1.66) for systems on a simple cubic lattice and as m(1.76) for an FePt Hamiltonian parametrized through ab initio calculations. The additional reduction in the scaling exponent, as compared to the mean-field theory (A similar to m(2)), comes from the nonlinear spin-wave effects.

AB - For finite-temperature micromagnetic simulations the knowledge of the temperature dependence of the exchange stiffness plays a central role. We use two approaches for the calculation of the thermodynamic exchange parameter from spin models: (i) based on the domain-wall energy and (ii) based on the spin-wave dispersion. The corresponding analytical and numerical approaches are introduced and compared. A general theory for the temperature dependence and scaling of the exchange stiffness is developed using the classical spectral density method. The low-temperature exchange stiffness A is found to scale with magnetization as m(1.66) for systems on a simple cubic lattice and as m(1.76) for an FePt Hamiltonian parametrized through ab initio calculations. The additional reduction in the scaling exponent, as compared to the mean-field theory (A similar to m(2)), comes from the nonlinear spin-wave effects.

KW - GREEN FUNCTION THEORY

KW - HEISENBERG-FERROMAGNET

KW - SYSTEMS

KW - NANOSTRUCTURES

KW - EQUATION

KW - FEPT

UR - http://www.scopus.com/inward/record.url?scp=78049409695&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.82.134440

DO - 10.1103/PhysRevB.82.134440

M3 - Article

SN - 1098-0121

VL - 82

SP - -

JO - Physical Review B

JF - Physical Review B

IS - 13

M1 - 134440

ER -