Nowak, Ulrich

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Nowak
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Ulrich
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Current-induced domain wall motion including thermal effects based on Landau-Lifshitz-Bloch equation

2009, Schieback, Christine, Hinzke, Denise, Kläui, Mathias, Nowak, Ulrich, Nielaba, Peter

We employ the Landau-Lifshitz-Bloch (LLB) equation to investigate current-induced domain wall motion at finite temperatures by numerical micromagnetic simulations. We extend the LLB equation with spin torque terms that account for the effect of spin-polarized currents and we find that the velocities depend strongly on the interplay between adiabatic and non-adiabatic spin torque terms. As a function of temperature, we find non-monotonous behavior, which might be useful to determine the relative strengths of the spin torque terms experimentally.

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Temperature-dependent magnetic properties of FePt : Effective spin Hamiltonian model

2005, Mryasov, Oleg N., Nowak, Ulrich, Guslienko, Konstantin, Chantrell, Roy W.

A model of magnetic interactions in the ordered ferromagnetic 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 (Fe, Pt) resolved contributions to the MAE have been distinguished with small Fe easy-plane and large Pt easy-axis terms. This model has been tested against available experimental data on the temperature dependence of MAE showing scaling of uniaxial MAE (K-1(T)) with magnetization (M(T)) K-1(T) similar to M(T)(gamma) characterized by the unusual exponent of gamma = 2.1. It is shown that this unusual behavior of the FePt can be quantitatively explained within the proposed model and originates from an effective anisotropic exchange mediated by the induced 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.