Exchange bias relaxation in reverse magnetic fields

Abstract

The time dependence associated with the so-called exchange bias in coupled polycrystalline ferromagnetic/ antiferromagnetic films has been suspected as arising from antiferromagnetic domain dynamics. In this paper we present a quantitative description of the nucleation and growth of antiferromagnetic domains based on the Kolmogorov-Avrami model, which describes the time dependence of the exchange bias in all the systems for which data could be found.

Activation of antiferromagnetic domain switching in exchange-coupled Fe/CoO/MgO(001) systems

“…This trend is very different from the training effect in exchange bias, which usually exhibits a dramatic decrease in the first few cycles [14][15][16][17].…”

Characterization and analysis of the training effect of exchange bias in coupled NiFe∕IrMn bilayers

“…In our previous study 16 of exchange bias relaxation in the presence of a constant strong reverse magnetic field, the domains are constantly growing and the domain size is described as a power law of time, s͑t − ͒ = c͑t − ͒ ␥ , with c the domain growth speed and ␥ Ͼ 0. However, in the training effect study with the magnetization changing its direction, the size of the AF domains can either increase or decrease at a given time and then s͑t − ͒ is not a monotonic function of time.…”

“…At subsequent times, the exchange bias field H e was measured by the shift of the hysteresis loop providing a time dependence of the exchange bias. 16 The training effect has been widely characterized by a power-law function of time. In fact, the underlying mechanism for these results is the same as that leading to the exchange bias reduction and reversal observed in the earlier experiments performed by Heijden et al 14,15 and explained in our previous study.…”

Field dependence of antiferromagnetic domain switching in epitaxial Fe/CoO/MgO(001) systems

“…AFM domain evolution has been previously explored to a certain extent in exchange bias phenomenon as a function of time (usually referred to as the training effect) [19,20,21,22]. However, the random spin orientations of AFM polycrystalline grains, which are usually employed for such studies, complicate the spin switching, prohibiting an explicit exploration of the AFM spin switching process.…”