Europhys. Lett.
Volume 69, Number 5, March 2005
Page(s) 805 - 811
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 09 February 2005
Europhys. Lett., 69 (5), pp. 805-811 (2005)
DOI: 10.1209/epl/i2004-10404-2

Temperature-dependent magnetic properties of $\chem{FePt}$: Effective spin Hamiltonian model

O. N. Mryasov, U. Nowak, K. Y. Guslienko and R. W. Chantrell

Seagate Research - 1251 Waterfront Place, Pittsburgh, PA 15222, USA

received 8 November 2004; accepted 22 December 2004
published online 9 February 2005

A model of magnetic interactions in the ordered ferromagnetic $\chem{FePt}$ is proposed on the basis of first-principles calculations of non-collinear magnetic configurations and shown to be capable of explaining recent measurements of magnetic-anisotropy energy (MAE). The site ($\chem{Fe}$,$\chem{Pt}$) resolved contributions to the MAE have been distinguished with small $\chem{Fe}$ easy-plane and large $\chem{Pt}$ easy-axis terms. This model has been tested against available experimental data on the temperature dependence of MAE showing scaling of uniaxial MAE (K1(T)) with magnetization (M(T)) $K_{1}(T)\sim
M(T)^{\gamma}$ characterized by the unusual exponent of $\gamma=2.1$. It is shown that this unusual behavior of the $\chem{FePt}$ can be quantitatively explained within the proposed model and originates from an effective anisotropic exchange mediated by the induced $\chem{Pt}$ moment. The latter is expected to be a common feature of 3d-5d(4d) alloys having 5d/4d elements with large spin-orbit coupling and exchange-enhanced Stoner susceptibility.

75.30.Gw - Magnetic anisotropy.
75.50.Ss - Magnetic recording materials.
71.15.Rf - Relativistic effects.

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