Temperature study of the spin-transfer switching speed from dc to 100ps

Abstract

We study the speed of the magnetization switching resulting from spin transfer in pillar-shaped CoFe∕Cu∕CoFe spin valves and the temperature dependence thereof. The switching speed was investigated with current pulses of durations from 100ps to dc while the temperature was varied from 50to300K. Quasistatic loops indicate that the reversal events imply transition states with reduced remanences. Their interval of occurrence shrinks gradually to almost null when the temperature is raised to 300K. The curvature of resistance versus current hysteresis loops is different in the antiparallel and parallel branches, which evidences the influence of the Ampere field on the quasistatic micromagnetic configuration. In the dynamical regime, the pulse-induced parallel to antiparallel transition speed is not much temperature dependent from 50to300K. In contrast, the pulse-induced antiparallel to parallel transition is thermally disfavored and much faster at 150K than at 300K. We model the experimental behavior by a competition between thermal fluctuations and the Ampere-field-related C-like bending of the magnetization in the free layer. The contribution of the Ampere field dominates in most cases. These contributions are amplified or damped together by the spin-transfer torque, but since the C-like bending is a response to a magnetic field, it sets in at a gradual pace ruled by the classical Gilbert relaxation. Most of the difference between quasistatic switching and pulse-induced switching results from this complete or incomplete alignment with the total effective field. Our demonstration of 100-ps switching validates spin-transfer switching for fast memory applications.

Distribution of the magnetization reversal duration in subnanosecond spin-transfer switching

“…However, previous investigations have concluded that the reversal speed in the sub-ns regime has insufficient reproducibility. This has first been interpreted qualitatively as resulting from classical thermal fluctuations [11], but reliable predictions are not yet available .…”

Crystallographically amorphous ferrimagnetic alloys: Comparing a localized atomistic spin model with experiments

“…The fastest precessional reversal demonstrated experimentally using an external magnetic field 2,3 is ∼100 ps, with similar reversal times achieved using a spin-polarized current. [4][5][6] Recent experimental work in the field of magneto-optics has demonstrated that carefully shaped laser pulses can be used to manipulate the magnetization dynamics on the subpicosecond time scale [7][8][9][10][11][12] in many materials, including cobalt, iron, nickel, and GdFeCo. However, controllable magnetization switching has only been observed in GdFeCo, and this has stimulated a great deal of effort to attempt on many levels to explain the process.…”

Understanding Nanoscale Temperature Gradients in Magnetic Nanocontacts

“…Unfortunately, STT requires huge current densities, which can lead to substantial heating and early material fatigue. STT may also assist the magnetization switching in nanopillar geometries [4,5], and it can increase the magnetization thermal noise [6], degrading the device performances. In nanopillar geometries, the magnetization dynamics takes place in a very confined region where the temperature is almost uniform [7], such that the temperature dynamics could be understood from simple experiments [5].…”