Time-Resolved Reversal of Spin-Transfer Switching in a Nanomagnet

Abstract

Time-resolved measurements of spin-transfer-induced (STI) magnetization reversal were made in current-perpendicular spin-valve nanomagnetic junctions subject to a pulsed current bias. These results can be understood within the framework of a Landau-Lifshitz-Gilbert equation that includes STI corrections and a Langevin random field for finite temperature. Comparison of these measurements with model calculations demonstrates that spin-transfer induced excitation is responsible for the observed magnetic reversal in these samples.

Reducing the switching current with a Gilbert damping constant in nanomagnets with perpendicular anisotropy

“…1,2 This technique can be used to develop non-volatile memory with both high-speed magnetization switching and low power consumption, e.g., spin-torque magnetoresistive random access memory (spin-RAM). There have been many theoretical reports on magnetization switching 3,4 and experimental studies of in-plane [5][6][7] and out-of-plane [8][9][10][11][12][13][14][15] magnetization magnets. To realize high-density spin-RAM, a low-magnetization switching current is required for the writing process, and a high thermal stability factor (D) is required to retain the information record.…”

Depinning probability of a magnetic domain wall in nanowires by spin-polarized currents

“…The fitting curve with the inverse relation, that is, j c -j c0 p1/t p , which is true for CIMS in nanopillars 7,9,11 , is also shown in the figure (dotted line). This relation is based on magnetization reversal originating from the current-induced torque through conservation of spin angular momentum 7 . In addition, a result of a one-dimensional Landau-Lifshitz-Gilbert calculation is shown (solid line).…”

“…As the key ingredient of these devices is current-induced displacement of DWs from one artificially prepared pinning site to another, it is very important to characterize the depinning properties, especially its probability and the relationship between the critical current and pulse duration in the nanosecond range. Whereas a theoretical model to address such issues for CIMS has been established 11,12 and confirmed in several experiments 7,9,10 , there has only been a few theoretical studies on CIDWM 16,17 .…”

“…There are mainly two ways to utilize the STT: one is current-induced magnetization switching (CIMS) in magnetic nanopillars 2,[7][8][9][10][11][12] , and the other is current-induced domain wall motion (CIDWM) in magnetic nanowires 1,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] . In particular, the latter is promising for applications in which a domain wall (DW) moves numerous times within several nanoseconds' duration 4 , or in which numerous DWs are shifted simultaneously 6 .…”

Time-resolved magnetic relaxation of a nanomagnet on subnanosecond time scales

“…It is now well known that spin-polarized currents and spin-transfer torques (STTs) can reverse the direction of the magnetization on subnanosecond timescales 1,9 . In fact, many experimental methods have been developed to study spin-transfer switching in both spin valves and magnetic tunnel junctions (MTJs).…”