Room temperature magnetic barrier layers in magnetic tunnel junctions

Abstract

We investigate the spin transport and interfacial magnetism of magnetic tunnel junctions with highly spin polarized ${\text{La}}_{0.7}{\text{Sr}}_{0.3}{\text{MnO}}_{3}$ (LSMO) and ${\text{Fe}}_{3}{\text{O}}_{4}$ electrodes and a ferrimagnetic ${\text{NiFe}}_{2}{\text{O}}_{4}$ (NFO) barrier layer. The spin-dependent transport can be understood in terms of magnon-assisted spin-dependent tunneling where the magnons are excited in the barrier layer itself. The $\text{NFO}/{\text{Fe}}_{3}{\text{O}}_{4}$ interface displays strong magnetic coupling, while the LSMO/NFO interface exhibits clear decoupling as determined by a combination of x-ray absorption spectroscopy and x-ray magnetic circular dichroism. This decoupling allows for distinct parallel and antiparallel electrode states in this all-magnetic trilayer. The spin transport of these devices, dominated by the NFO barrier layer magnetism, leads to a symmetric bias dependence of the junction magnetoresistance at all temperatures.