Exchange bias and training effects in antiferromagnetically coupled La0.7Sr0.3MnO3 / SrRuO3 superlattices

TL;DR

This study investigates exchange bias and training effects in La0.7Sr0.3MnO3 / SrRuO3 superlattices, revealing strong antiferromagnetic coupling and how repeated cycling influences magnetic properties across a broad temperature range.

Contribution

It provides a detailed experimental analysis of exchange bias and training effects in these superlattices, supported by a theoretical model explaining the observed phenomena.

Findings

Strong AFM interlayer coupling evidenced by AC susceptibility

Significant decrease in exchange bias field with cycling

Excellent agreement between theory and experiment on training effects

Abstract

Exchange bias (EB) and the training effects (TE) in an antiferromagnetically coupled La0.7Sr0.3MnO3 / SrRuO3 superlattices were studied in the temperature range 1.8 - 150 K. Strong antiferromagnetic (AFM) interlayer coupling is evidenced from AC - susceptibility measurements. Below 100 K, vertical magnetization shifts are present due to the two remanent states corresponding to the two ferromagnetic (FM) layers at FM and AFM coupling condition. After field cooling (FC), significant decrease in the exchange bias field (HEB) is observed when cycling the system through several consecutive hysteresis loops. Quantitative analysis for the variation of HEB vs. number of field cycles (n) indicates an excellent agreement between the theory, based on triggered relaxation phenomena, and our experimental observations. Nevertheless, the crucial fitting parameter K indicates smooth training effect upon repeated field cycling, in accordance with our observation.