Magnetic coupling in mesoscopic metal/ferromagnet layered systems

TL;DR

This paper investigates a mesoscopic exchange interaction mechanism in layered metal/ferromagnet systems, revealing that the exchange energy's sign and magnitude are sample-specific and controllable via external parameters, with size-independent variance in certain geometries.

Contribution

It introduces a mesoscopic mechanism for exchange interaction in layered systems, showing controllability and size-independent variance in specific geometries.

Findings

Exchange energy sign and magnitude are sample-specific and controllable.

External magnetic fields and superconducting phase differences influence exchange energy.

Variance of exchange energy is size-independent in certain geometries.

Abstract

We consider a mesoscopic mechanism of the exchange interaction in a system of alternating ferromagnetic/nonmagnetic metallic layers. In the case of small mesoscopic samples the sign and the amplitude of the exchange energy turn out to be random sample specific quantities. They can be changed by applying an external magnetic field, by attaching to the system superconducting electrodes with different phases of the superconducting order parameter and by changing the chemical potential of electrons in the matal with the help of a gate. In the case of square or cubic geometries of the nonmagnetic layer at low temperature the variance of the exchange energy turns out to be sample size independent.