Investigation on the Effect of Femtosecond Laser Induced Spin Transfer Torque of GdFeCo Alloy

Haozhe Huang,Weiming Cheng,Zhihao Zeng,Rongyao Wang,Xinyu Zhang,Haiwei Wang,Changsheng Xie

doi:10.3390/app11146501

Abstract

All-optical magnetic switching (AOS) provides a novel approach to improve writing ability and energy efficiency compared to those utilized in the mainstream magnetic data storage products. Rare earth-transition metals (RE-TM) exhibit extremely fast magnetization switching induced by one single incident linearly polarized laser pulse; however, the mechanism is still ambiguous. Here, we show by atomistic spin simulation that the laser induced spin transfer torque dominates the magnetization reversal of Fe sublattice in Gd25Fe75 alloy, and that the switching speed of Gd25Fe75 alloy is relevant to the amount of spin current. This implies that a possible helicity independent mechanism underlies the RE-TM alloy AOS process. We also find that the greater the spin current density the faster the magnetization switching, and the time magnetization reversal of Gd and Fe takes is also affected by the spin current density.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The results show that the spin transfer torque may be the critical factor that causes reversal of spin magnetization of Fe sublattice prior to Gd sublattice during helicity, independent of photomagnetization of GdFeCo amorphous alloy films
We suggested a new physical mechanism undertaking the All-optical magnetic switching (AOS) process in GdFeCo amorphous alloy thin film: the spin transfer torque induced by femtosecond laser single pulse acts on the spins of Fe, leading to the reversal of Fe spins’ orientation first; the electronic temperature quickly dropped below the Curie temperature, and the exchange interaction between Fe and Gd sublattices makes Gd spins switch

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The exploding amount of data is devouring the capacity of storage devices and demanding ever faster read/write speed of these devices. Most of the data generated is stored on hard disk drives. The recording density of these drives is approaching the limit of the magnetic material due to the superparamagnetic effect [1]

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Conclusion