Coercivity and random interfacial exchange coupling in CoPt/Co films

TL;DR

This paper investigates how the coercivity and exchange bias in CoPt/Co bilayers depend on the hard layer's magnetization and domain state, revealing tunable magnetic properties relevant for spintronic applications.

Contribution

It demonstrates the linear and quadratic dependencies of exchange bias and coercivity on the hard layer magnetization and domain randomness, supported by experiments and simulations.

Findings

Exchange bias field depends linearly on hard layer magnetization.

Coercivity shows quadratic dependence on hard layer magnetization.

Hard layer domain randomness primarily influences soft layer coercivity.

Abstract

Hard-soft bilayers are analogous to prototype exchange-biased ferromagnetic -antiferromagnetic systems as the minor loop of the soft layer is biased by the hard and furthermore they offer bias layer tunability. In sputtered CoPt/Co hard-soft bilayers we demonstrate that the exchange bias field shows a linear dependence on the hard layer magnetization, while the coercivity shows a quadratic dependence. Analysis of the minor hysteresis loop features supported by Monte-Carlo simulations provide clear evidence that the coercivity of the soft layer is mainly determined by the tunable randomness of the domain state of the hard layer.