Magnetocaloric effect at the reorientation of the magnetization in ferromagnetic multilayers with perpendicular anisotropy

TL;DR

This paper explores the magnetocaloric effect in ferromagnetic multilayers with perpendicular anisotropy, demonstrating how magnetization reorientation can induce significant entropy changes with lower magnetic fields.

Contribution

It introduces a method to predict and enhance the magnetocaloric effect in exchange-coupled multilayers with perpendicular anisotropy using micromagnetic modeling.

Findings

Entropy change of 0.34 Jkg$^{-1}$K$^{-1}$ predicted for MnBi-Co multilayers.

Lower magnetic fields (by an order of magnitude) can induce the effect in thin multilayers.

Reorientation of magnetization leads to a measurable magnetocaloric effect in engineered multilayers.

Abstract

We investigate the magnetocaloric effect obtained by the rotation of a magnetic field applied to an exchange-coupled multilayer system composed of two different ferromagnetic (FM) materials. We specifically consider a system in which the two FMs have perpendicular uniaxial anisotropy axes and utilise conditions which yield a reorientation of the total magnetization when compensation between the anisotropies of the two layers occurs. We calculate the consequent entropy change associated with the "artificial" reorientation. By using known parameters from MnBi and Co we predict an entropy change of $\Delta s = 0.34$ Jkg$^{-1}$K$^{-1}$ for perfect coupling. Lastly, we study the behavior of the multilayer under a rotating magnetic field via a micromagnetic model. When the layer thicknesses are of the order of the local domain wall width, the magnetic field-induced entropy change can be obtained with magnetic fields one order of magnitude lower than in the uncoupled case.