Abstract
The goal of this paper is to investigate the short time-scale, thermally-induced probability of magnetization reversal for an biaxial nanomagnet that is characterized with a biaxial magnetic anisotropy. For the first time, we clearly show that for a given energy barrier of the nanomagnet, the magnetization reversal probability of an biaxial nanomagnet exhibits a non-monotonic dependence on its saturation magnetization. Specifically, there are two reasons for this non-monotonic behavior in rectangular thin-film nanomagnets that have a large perpendicular magnetic anisotropy. First, a large perpendicular anisotropy lowers the precessional period of the magnetization making it more likely to precess across the x^=0 plane if the magnetization energy exceeds the energy barrier. Second, the thermal-field torque at a particular energy increases as the magnitude of the perpendicular anisotropy increases during the magnetization precession. This non-monotonic behavior is most noticeable when analyzing the magnetization reversals on time-scales up to several tens of ns. In light of the several proposals of spintronic devices that require data retention on time-scales up to 10’s of ns, understanding the probability of magnetization reversal on the short time-scales is important. As such, the results presented in this paper will be helpful in quantifying the reliability and noise sensitivity of spintronic devices in which thermal noise is inevitably present.
Highlights
The interaction of the magnetic order parameter with the underlying thermal fluctuations of the magnetic body has been analyzed extensively in prior literature.[1,2,3,4] Most prominently, W
We consider two cases of the instability in magnetization resulting from the thermal noise that eventually lead to magnetization reversal within a given time period
We find that the reversal probability in Case-II varies non-monotonically with the demagnetization energy. This is because a larger perpendicular anisotropy shapes the energy orbit, minimizing its zcomponents, and allows the thermal field to induce a greater torque on the magnetization
Summary
The interaction of the magnetic order parameter with the underlying thermal fluctuations of the magnetic body has been analyzed extensively in prior literature.[1,2,3,4] Most prominently, W. We consider two cases of the instability in magnetization resulting from the thermal noise that eventually lead to magnetization reversal within a given time period. These two cases of thermal reversals are defined as follows. We find that the reversal probability in Case-II varies non-monotonically with the demagnetization energy This is because a larger perpendicular anisotropy shapes the energy orbit, minimizing its zcomponents, and allows the thermal field to induce a greater torque on the magnetization. We test the limits of this non-monotonic behavior and show that while this behavior is especially present in small-time scale (sub-100 ns) measurements, it is diminished at very large time-scales
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