Spintronics with multiferroics

TLDR

Exchange coupling mechanisms in multiferroics enable electrical control of magnetization, offering a route to logic state manipulation in spintronic devices. This review surveys the functionalization of multiferroics for spintronics, focusing on recent studies of BiFeO3 and (La,Bi)MnO3 as active tunnel barriers. The authors examine BiFeO3 integration into various architectures and the use of (La,Bi)MnO3 as a ferromagnetic/ferroelectric tunnel barrier in magnetic tunnel junctions with Au and (La,Sr)MnO3 electrodes. BiFeO3 tunnel barriers yield large tunnel magnetoresistance and exchange coupling with ferromagnets, while (La,Bi)MnO3 barriers produce four‑resistance‑state devices that combine spin filtering and ferroelectric polarization, illustrating how ferroelectric control adds new functionalities to spintronic memory.

Abstract

In this paper, we review the recent research on the functionalization of multiferroics for spintronics applications. We focus more particularly on antiferromagnetic and ferroelectric BiFeO3 and its integration in several types of architectures. For instance, when used as a tunnel barrier, BiFeO3 allows the observation of a large tunnel magnetoresistance with Co and (La,Sr)MnO3 ferromagnetic electrodes. Also, its antiferromagnetic and magnetoelectric properties have been exploited to induce an exchange coupling with a ferromagnet. The mechanisms of such an exchange coupling open ways to electrically control magnetization and possibly the logic state of spintronics devices. We also discuss recent results concerning the use of ferromagnetic and ferroelectric (La,Bi)MnO3 as an active tunnel barrier in magnetic tunnel junctions with Au and (La,Sr)MnO3 electrodes. A four-resistance-state device has been obtained, with two states arising from a spin filtering effect due to the ferromagnetic character of the barrier and two resulting from the ferroelectric behavior of the (La,Bi)MnO3 ultrathin film. These results show that the additional degree of freedom provided by the ferroelectric polarization brings novel functionalities to spintronics, either as a extra order parameter for multiple-state memory elements, or as a handle for gate-controlled magnetic memories.