Femtosecond laser-heating effect on the magnetization dynamics in perpendicularly magnetized Ta/CoFeB/MgO film

Bo Liu,Xuezhong Ruan,Long Yang,Jing Wu,Hao Meng,Jian-Wang Cai,Liang He,Yongbing Xu

doi:10.1088/1367-2630/ab1fac

Abstract

We have studied the effect of ultrafast laser-heating on the magnetization dynamics of perpendicularly magnetized CoFeB film by means of the time-resolved magneto-optical Kerr rotation effect. The effective perpendicular magnetic anisotropy field is significantly decreased with enhancing the pump laser-fluence in a moderate range of 5–12 mJ cm−2. The Gilbert damping, however, is found to be independent of the pump fluence. These findings provide a new method of separately manipulating the Gilbert damping and perpendicular magnetic anisotropy.

Highlights

The magnetic films with perpendicular magnetic anisotropy (PMA) are the promising candidates in the application of the next-generation, high-density magnetic information storage technology due to their high thermal stability
We report the effect of transient laser heating on the magnetic anisotropy and Gilbert damping in perpendicularly magnetized Ta/CoFeB/MgO film by using the time-resolved magneto-optical Kerr effect (TRMOKE) techniques
For better understanding the behavior of HK and a0 in the PMA CoFeB thin film under different pump irradiation fluences, we provide a possible explanation for the irrelevance between a0 and HK

Summary

Introduction

The magnetic films with perpendicular magnetic anisotropy (PMA) are the promising candidates in the application of the next-generation, high-density magnetic information storage technology due to their high thermal stability. With STT, the critical current density for magnetization switching in the case of perpendicular magnetized magnetic tunneling junctions (MTJs) is directly proportional to the Gilbert damping constant and PMA. This proportionality shows that a balance between the thermal stability and writability of magnetization is required. Materials with large PMA and weak Gilbert damping are preferred. Materials with large PMA exhibit large damping values such as Co/Pt multilayers [6] and CoCrPt alloys [7]

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Conclusion