Quantum-well tunneling anisotropic magnetoresistance above room temperature

TL;DR

This paper demonstrates room-temperature tunneling anisotropic magnetoresistance in quantum wells integrated into magnetic tunnel junctions, showing significant control of quantum states via magnetization rotation with potential applications in spintronics.

Contribution

It introduces the observation of QW-TAMR effect above room temperature and shows magnetic control of quantum well states in MTJs, a novel advancement in spintronic device research.

Findings

QW-TAMR ratio of up to 5.4% at 5K

QW-TAMR persists with 1.2% at 380K

Magnetization rotation significantly shifts QW levels

Abstract

Quantum-well (QW) devices have been extensively investigated in semiconductor structures. More recently, spin-polarized QWs were integrated into magnetic tunnel junctions (MTJs). In this work, we demonstrate the spin-based control of the quantized states in iron $3d$-band QWs, as observed in experiments and theoretical calculations. We find that the magnetization rotation in the Fe QWs significantly shifts the QW quantization levels, which modulate the resonant-tunneling current in MTJs, resulting in a tunneling anisotropic magnetoresistance (TAMR) effect of QWs. This QW-TAMR effect is sizable compared to other types of TAMR effect, and it is present above the room-temperature. In a QW MTJ of Cr/Fe/MgAl$_2$O$_4$/top electrode, where the QW is formed by a mismatch between Cr and Fe in the $d$ band with $\Delta_1$ symmetry, a QW-TAMR ratio of up to 5.4 % was observed at 5 K, which persisted to 1.2 % even at 380K. The magnetic control of QW transport can open new applications for spin-coupled optoelectronic devices, ultra-thin sensors, and memories.