Thermoelectrical manipulation of nanomagnets

TL;DR

This paper explores how Joule heating can be used to control magnetic states in nanostructures, enabling thermally driven switching and oscillations in magnetic multilayer devices with potential applications in spintronics.

Contribution

It introduces a theoretical and experimental framework for thermally manipulating nanomagnets via Joule heating, including the design of devices for controlled magnetic switching and oscillations.

Findings

Thermal control of magnetic state switching demonstrated.

Joule heating can reversibly drive spacer through Curie point.

Magneto-resistance oscillations tunable from DC to GHz.

Abstract

We investigate the interplay between the thermodynamic properties and spin-dependent transport in a mesoscopic device based on a magnetic multilayer (F/f/F), in which two strongly ferromagnetic layers (F) are exchange-coupled through a weakly ferromagnetic spacer (f) with the Curie temperature in the vicinity of room temperature. We show theoretically that the Joule heating produced by the spin-dependent current allows a spin-thermo-electronic control of the ferromagnetic-to-paramagnetic (f/N) transition in the spacer and, thereby, of the relative orientation of the outer F-layers in the device (spin-thermo-electric manipulation of nanomagnets). Supporting experimental evidence of such thermally controlled switching from parallel to antiparallel magnetization orientations in F/f(N)/F sandwiches is presented. Furthermore, we show theoretically that local Joule heating due to a high concentration of current in a magnetic point contact or a nanopillar can be used to reversibly drive the weakly ferromagnetic spacer through its Curie point and thereby exchange couple and decouple the two strongly ferromagnetic F-layers. For the devices designed to have an antiparallel ground state above the Curie point of the spacer, the associated spin-thermionic parallel-to-antiparallel switching causes magneto-resistance oscillations whose frequency can be controlled by proper biasing from essentially DC to GHz. We discuss in detail an experimental realization of a device that can operate as a thermo-magneto-resistive switch or oscillator.