Role of longitudinal fluctuations in L$1_0$ FePt

Abstract

L$1_0$ FePt is a technologically important material for a range of novel data storage applications. In the ordered FePt structure the normally non-magnetic Pt ion acquires a magnetic moment, which depends on the local field originating from the neighboring Fe atoms. In this work a model of FePt is constructed, where the induced Pt moment is simulated by using combined longitudinal and rotational spin dynamics. The model is parameterized to include a linear variation of the moment with the exchange field, so that at the Pt site the magnetic moment depends on the Fe ordering. The Curie temperature of FePt is calculated and agrees well with similar models that incorporate the Pt dynamics through an effective Fe-only Hamiltonian. By computing the dynamic correlation function the anisotropy field and the Gilbert damping are extracted over a range of temperatures. The anisotropy exhibits a power-law dependence with temperature with exponent $n\approx 2.1$. This agrees well with what observed experimentally and it is obtained without including a two-ion anisotropy term as in other approaches. Our work shows that incorporating longitudinal fluctuations into spin dynamics calculations is crucial for understanding the properties of materials with induced moments.

arXiv comment9 pages, 9 figures

References in corpus (8)

• Atomistic spin model simulations of magnetic nanomaterials
• Temperature dependent magnetic properties of FePt: effective spin Hamiltonian model
• All-optical switching in granular ferromagnets caused by magnetic circular dichroism
• The Landau-Lifshitz equation in atomistic models
• Ultrafast demagnetization of Pt magnetic moment in L1${}_0$-FePt probed by hard x-ray free electron laser
• Switching times of nanoscale FePt: finite size effects on linear reversal mechanism
• Extended spin model in atomistic simulations of alloys
• Non-trivial spatial dependence of the spin torques in L1${}_0$ FePt-based tunnelling junctions

Cited by in corpus (3)

• Modeling coupled spin and lattice dynamics
• Temperature scaling of two-ion anisotropy in pure and mixed anisotropy systems
• Generalised form of the magnetic anisotropy field in micromagnetic and atomistic spin models