Current-induced magnetic superstructures in exchange-spring devices

TL;DR

This paper explores how a magneto-thermo-electric instability in a layered magnetic device can induce and control magnetic superstructures, leading to potential applications like precise current stabilization.

Contribution

It introduces a novel method to generate and manipulate magnetic superstructures using Joule heating-induced instabilities in exchange-spring multilayers.

Findings

Spatial instability occurs when sample length exceeds ~10 μm.

Magnetization forms a moving domain controllable by bias voltage.

Device exhibits a plateau in current-voltage characteristics with hysteresis.

Abstract

We investigate the potential to use a magneto-thermo-electric instability that may be induced in a mesoscopic magnetic multi-layer (F/f/F) to create and control magnetic superstructures. In the studied multilayer two strongly ferromagnetic layers (F) are coupled through a weakly ferromagnetic spacer (f) by an "exchange spring" with a temperature dependent "spring constant" that can be varied by Joule heating caused by an electrical dc current. We show that in the current-in-plane (CIP) configuration a distribution of the magnetization, which is homogeneous in the direction of the current flow, is unstable in the presence of an external magnetic field if the length L of the sample in this direction exceeds some critical value Lc ~ 10 \mu m. This spatial instability results in the spontaneous formation of a moving domain of magnetization directions, the length of which can be controlled by the bias voltage in the limit L >> Lc. Furthermore, we show that in such a situation the current-voltage characteristics has a plateau with hysteresis loops at its ends and demonstrate that if biased in the plateau region the studied device functions as an exponentially precise current stabilizer.