Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys.

Fanghua Tian,Rui Zhang,Chao Zhou,Minwei Xu,Kaiyan Cao,Yuyang Zeng,Tieyan Chang,Yin Zhang,Sen Yang,Xiaoping Song

doi:10.1038/srep30801

Abstract

A spontaneous exchange bias (SEB) discovered by Wang et al. [Phys. Rev. Lett. 106 (2011) 077203.] after zero-field cooling (ZFC) has attracted recent attention due to its interesting physics. In this letter, we report a giant SEB tuned by Sb-doping in Ni50Mn38Ga12-xSbx Heusler alloys. Such an SEB was switched on below the blocking temperature of approximately 50 K. The maximum exchange bias HE can arrive at 2930 Oe in a Ni50Mn38Ga10Sb2 sample after ZFC to 2 K. Further studies showed that this SEB was attributable to interaction of superspin glass (SSG) and antiferromagnetic matix, which was triggered by the crossover of SSG from canonical spin glass to a cluster spin glass. Our results not only explain the underlying physics of SEB, but also provide a way to tune and control the SEB performance.

Highlights

A spontaneous exchange bias (SEB) discovered by Wang et al [Phys
spontaneous EB (SEB) continuous tuning was demonstrated in Ni50Mn38Ga12-xSbx (x = 0–6) alloys, and the largest HE (~2930 Oe) was obtained in the Ni50Mn38Ga10Sb2 sample
The largest SEB is observed in the Ni50Mn38Ga10Sb2 sample

Summary

Introduction

A spontaneous exchange bias (SEB) discovered by Wang et al [Phys. Rev. Exchange bias (EB) is demonstrated as the magnetic hysteresis loop shifts from the origin, which is usually induced by field cooling (FC) to form a unidirectional magnetic anisotropy at the interface between ferromagnetic (FM) and antiferromagnetic (AFM) phases. SEB was first reported in NiMnIn alloys by Wang et al.[11] in 2011 and was attributed to a superferromagnetic (SFM) unidirectional anisotropy formed at the interface between superparamagnetic (SPM) domains and the AFM matrix. This SEB was subsequently explored in other magnetic systems and several different mechanisms were proposed. Abundant physical properties could be caused by the SPM or the SG11,13

Methods

Results

Conclusion