Training and recovery behaviours of exchange bias in FeNi/Cu/Co/FeMn spin valves at high field sweep rates

TL;DR

This study investigates how exchange bias in FeNi/Cu/Co/FeMn spin valves responds to high field sweep rates, revealing proportional relationships with training cycles and recovery time explained by thermal activation.

Contribution

It introduces a model based on thermal activation to explain training and recovery behaviors of exchange bias at high field sweep rates.

Findings

Training and recovery are proportional to the logarithm of cycles and time.

Relaxation times decrease with increasing sweep rates.

Shorter relaxation times compared to conventional measurements.

Abstract

Training and recovery of exchange bias in FeNi/Cu/Co/FeMn spin valves have been studied by magnetoresistance curves with field sweep rates from 1000 to 4800 Oe/s. It is found that training and recovery of exchange field are proportional to the logarithm of the training cycles and recovery time, respectively. These behaviours are explained within the model based on thermal activation. For the field sweep rates of 1000, 2000 and 4000 Oe/s, the relaxation time of antiferromagnet spins are 61.4, 27.6, and 11.5 in the unit of $ms$ respectively, much shorter than the long relaxation time (~10^2 s) in conventional magnetometry measurements.