Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer

TL;DR

This study explores how thermal variations influence exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves, demonstrating temperature-controlled magnetic states and proposing a device that integrates thermal switching with magnetoresistive readout.

Contribution

It introduces a method to thermally control exchange coupling in spin-valves using a Ni-Cu spacer with a tunable Curie point, enabling thermal switching of magnetic states.

Findings

Giant magnetoresistance disappears above ~30% Ni concentration due to mean free path reduction.

The Ni-Cu spacer's Curie point can be tuned near room temperature for thermal control.

A device combining thermal exchange control and magnetoresistance is successfully demonstrated.

Abstract

Thermal control of exchange coupling between two strongly ferromagnetic layers through a weakly ferromagnetic Ni-Cu spacer and the associated magnetoresistance is investigated. The spacer, having a Curie point slightly above room temperature, can be cycled between its paramagnetic and ferromagnetic states by varying the temperature externally or using joule heating. It is shown that the giant magnetoresistance vanishes due to a strong reduction of the mean free path in the spacer at above ~30 % Ni concentration -- before the onset of ferromagnetism. Finally, a device is proposed and demonstrated which combines thermally controlled exchange coupling and large magnetoresistance by separating the switching and the read out elements.