Positive to negative zero-field cooled exchange bias in La0.5Sr0.5Mn0.8Co0.2O3 ceramics.

Cui Shang,Shaopu Guo,Zhengcai Xia,Lingfang Xu,Haibo Xiao,Zhigang Sun,Ruilong Wang,Changping Yang

doi:10.1038/srep25703

Abstract

Exchange bias effect obtained after zero-field cooling from unmagnetized state usually exhibits a shift of hysteresis loop negative to the direction of the initial magnetic field, known as negative zero-field cooled exchange bias. Here, positive zero-field cooled exchange bias is reported in La0.5Sr0.5Mn0.8Co0.2O3 ceramics. In addition, a transition from positive to negative exchange bias has been observed with increasing initial magnetization field and measurement temperature. Based on a simple spin bidomain model with variable interface, two type of interfacial spin configuration formed during the initial magnetization process are proposed to interpret the observed phenomenon.

Highlights

Exchange bias effect obtained after zero-field cooling from unmagnetized state usually exhibits a shift of hysteresis loop negative to the direction of the initial magnetic field, known as negative zero-field cooled exchange bias
It is high unexpected to observe zero-field cooled exchange bias (EB) (ZFC-EB) effect, in another word, a shift of the magnetic hysteresis loop center away from zero field after zero-field cooling from unmagnetized state due to the formation of two oppositely oriented AFM domains
Though ZFC-EB effect with small HEB was reported in bilayer systems early[12], it receives wide acceptance until the observation of large ZFC-EB effect with HEB up to 1300 Oe in Ni50Mn37In13 alloy by wang et al.[13], in which the magnitude of the shift can be tuned by the strength of initial magnetization field

Summary

Introduction

Exchange bias effect obtained after zero-field cooling from unmagnetized state usually exhibits a shift of hysteresis loop negative to the direction of the initial magnetic field, known as negative zero-field cooled exchange bias. The appearance of such ZFC-EB effect is related to newly established interface with AFM unidirectional anisotropy, and the formation or growth of FM (or superferromagnet, SFM) domains at the expense of pinning subsystem (AFM matrix or spin glass) has been proposed as a possible way[13,16,17,18,19,20,21] Almost all these studies show only the negative ZFC-EB effect, in another word, shift of the hysteresis loop in the opposite direction to the initial magnetization field. In La0.5Sr0.5Mn0.8Co0.2O3 ceramics, which can be ascribed to the evolution of the interfacial spin configuration during the initial magnetization process

Methods

Results

Conclusion