Giant Vertical Magnetization Shift Caused by Field-Induced Ferromagnetic Spin Reconfiguration in Ni50Mn36Ga14 Alloy

Fanghua Tian,Zhonghai Yu,Chao Zhou,Qizhong Zhao,Yin Zhang,Adil Murtaza,Sen Yang,Wenliang Zuo,Xiaoping Song

doi:10.3390/ma13214701

Abstract

Vertical magnetization shift (VMS) is a special type of exchange bias effect that may lead to a revolution in future ultrahigh-density magnetic recording technology. However, there are very few reports focusing on the performance of VMS due to the unclear mechanism. In this paper, a giant vertical magnetization shift (ME) of 6.34 emu/g is reported in the Ni50Mn36Ga14 alloy. The VMS can be attributed to small ferromagnetic ordered regions formed by spin reconfiguration after field cooling, which are embedded in an antiferromagnetic matrix. The strong cooling-field dependence, temperature dependence, and training effect all corroborate the presence of spin reconfiguration and its role in the VMS. This work can enrich VMS research and increase its potential in practical applications as well.

Highlights

Since the discovery of the exchange bias effect, it has been utilized to fabricate hard disk drives, spin valves, magnetic tunnel junctions, and other “spin electronic” devices [1,2,3,4]
magnetization shift (ME) = 45 emu/cm3 in SrRuO3 /SrTiO3 heterostructures due to the lattice distortion caused by the oxygen deficiency, which modifies the strong hybridization of p-d orbitals and perpendicular uniaxial magnetic anisotropy [15]
It is known from the literature that the melting temperature of NiMnGa alloy is about 1300 K [30], so the annealing temperature used in this article was 1173 K

Summary

Introduction

Since the discovery of the exchange bias effect, it has been utilized to fabricate hard disk drives, spin valves, magnetic tunnel junctions, and other “spin electronic” devices [1,2,3,4]. EB is the offset of the hysteresis loop along the field axis, which is observed and studied in many materials [5,6,7,8,9,10,11,12]; VMS is the offset of the hysteresis loop along the magnetization axis, which is only found in a small number of systems [13,14,15,16,17,18]. ME denotes the shift of the center of gravity of the hysteresis loop along the magnetization axis. It is a measure of the average value of magnetizations at the positive and negative measuring fields (Mmax+ and Mmax− , respectively), ME = (Mmax+ + Mmax− )/2 [13,14,15]. The reported ME is relatively small, and a comprehensive understanding of the VMS effect is still disputed, restricting the practical applications of VMS

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Discussion

Conclusion