The Effect of Polarized Currents on the Critical Curve of Single-Domain Particles With Quartic Crystalline Anisotropy

Abstract

The use of polarized currents as tools for influencing the magnetic switching of magnetic materials was an important step in the evolution of modern recording technologies. A new paradigm was opened and new technologies based on this new idea have been developed. However, the modeling effort did not followed at the same pace the technological developments. In this paper, we are analyzing the effect on switching critical curves of the polarized current, which seems to be the most sensitive tool for the moment in evidencing these effects. The most important point of this paper is that we took into consideration the effect of higher order terms in the series expansion of the uniaxial anisotropy free energy and we analyze how these terms are influencing the critical curve shape. The results are discussed in terms of the efficiency of the polarized currents on the switching behavior of macrospins.

Landau-Lifshitz-Bloch-Slonczewski simulations of the spin-transfer-torque driven magnetization switching assisted by Joule heating

“…As we proved to be essential in the switching behavior, 21 we have taken two terms in the series expansion of the anisotropy free energy density…”

“…Consequently, materials with large K 2 appear to be less noisy from this regard, property useful in explaining recent experimental results. 7,21 The reverse may also happen. When the useful signal is polarized, it may be difficult for the current to avoid the influence of all the magnetic fields of neighboring magnetic substrates on the free layer.…”

“…This was tested using Henry's analytical parametric expressions for the critical curves 7 extended by us for materials with high k 2 (Ref. 21) and also for isothermal processes at different temperatures 24 with remarkable good agreement. (ii) This model was used to simulate the switching of the macrospin in a realistic case, when the Joule heating is taken into account as the source of temperature change during the passing of a polarized current.…”

Critical curves in NiFe/FeMn bilayers with varying antiferromagnetic layer thickness

“…An interesting approach to visualize the anisotropy in these materials is through the critical curve, a concept first introduced to find magnetization equilibrium positions [13,14] for a Stoner-Wohlfarth (SW) particle [15]. This angulardependent technique is based on the reversible susceptibility and has been studied both theoretically and experimentally for a variety of magnetic systems, including nanoparticles [16], thin films [17], multilayers [18], synthetic antiferromagnets [19,20], current-driven multilayers [21], systems with multiaxial anisotropies [22], and exchange bias [12,23,24]. The critical curve, in the case of exchange bias in particular, is interesting for studying the switching properties of a material or device.…”