Artificial control of the bias-voltage dependence of tunnelling-anisotropic magnetoresistance using quantization in a single-crystal ferromagnet

Iriya Muneta,Toshiki Kanaki,Masaaki Tanaka,Shinobu Ohya

doi:10.1038/ncomms15387

Abstract

A major issue in the development of spintronic memory devices is the reduction of the power consumption for the magnetization reversal. For this purpose, the artificial control of the magnetic anisotropy of ferromagnetic materials is of great importance. Here, we demonstrate the control of the carrier-energy dependence of the magnetic anisotropy of the density of states (DOS) using the quantum size effect in a single-crystal ferromagnetic material, GaMnAs. We show that the mainly twofold symmetry of the magnetic anisotropy of DOS, which is attributed to the impurity band, is changed to a fourfold symmetry by enhancing the quantum size effect in the valence band of the GaMnAs quantum wells. By combination with the gate electric-field control technique, our concept of the usage of the quantum size effect for the control of the magnetism will pave the way for the ultra-low-power manipulation of magnetization in future spintronic devices.

Highlights

A major issue in the development of spintronic memory devices is the reduction of the power consumption for the magnetization reversal
We demonstrate the artificial control of the carrier energy dependence of the magnetic anisotropy of the density of states (DOS) for the first time by designing quantum well structures consisting of a single-crystal ferromagnetic thin film and semiconductor barriers and tuning the strength of the quantum size effect
We reveal that the relative strength of the magnetic anisotropy between the valence band (VB) and impurity band (IB), which have fourfold and twofold symmetries in the film plane, respectively, can be varied by controlling the strength of the quantum size effect induced in the VB (Fig. 1)

Summary

Introduction

A major issue in the development of spintronic memory devices is the reduction of the power consumption for the magnetization reversal. At the peaks and dips of the dI/dV-V curves indicated by the blue and green arrows in Fig. 4b,e,h, the symmetry of the dI/dV-j curves shown in Fig. 4c,f,i is changed from twofold to fourfold as the resonant tunnelling is enhanced by decreasing d.

Results

Conclusion