Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers: a thermo-magnetic Curie-switch

TL;DR

This paper introduces a thermally controlled interlayer exchange coupling in ferromagnetic multilayers, enabling temperature-tunable magnetic switching for potential applications in sensors, oscillators, and memory devices.

Contribution

It presents a novel thermo-magnetic Curie-switch mechanism using Ni-Cu alloy spacers with gradient composition for improved switching performance.

Findings

Effective exchange coupling can be switched on and off by temperature control.

Gradient composition spacers improve uniformity and switching efficiency.

First-principles modeling captures proximity effects and atomic moment variations.

Abstract

We investigate a novel type of interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic tri-layer through the Curie point of the weakly ferromagnetic spacer, with the exchange coupling between the strongly ferromagnetic outer layers that can be switched, on and off, or varied continuously in magnitude by controlling the temperature of the material. We use Ni-Cu alloy of varied composition as the spacer material and model the effects of proximity-induced magnetism and the interlayer exchange coupling through the spacer from first principles, taking into account not only thermal spin-disorder but also the dependence of the atomic moment of Ni on the nearest-neighbor concentration of the non-magnetic Cu. We propose and demonstrate a gradient-composition spacer, with a lower Ni-concentration at the interfaces, for greatly improved effective-exchange uniformity and significantly improved thermo-magnetic switching in the structure. The reported magnetic multilayer materials can form the base for a variety of novel magnetic devices, such as sensors, oscillators, and memory elements based on thermo-magnetic Curie-switching in the device.