Interfacial Oxidation Enhanced Perpendicular Magnetic Anisotropy in Low Resistance Magnetic Tunnel Junctions Composed of Co/Pt Multilayer Electrodes

Abstract

Low-resistance magnetic tunnel junctions utilizing perpendicular magnetic anisotropy of Co/Pt multilayer electrodes have been investigated. In these junctions, AlO x tunnel barrier has been prepared by repeated natural oxidation processes. Each natural oxidation process has been optimized by varying the thickness of pre-oxidized Al layer prior to oxidation. The perpendicular magnetic anisotropy of Co/Pt multilayer has been found to be dependent on the degree of oxidation at the interface of tunnel barrier and Co adjacent layer. It has been observed that magnetization of Co/Pt multilayer is tilted when Co layer adjacent to tunnel barrier is relatively thick, which is attributed to the lack of interfacial anisotropy contribution near the interface of Co adjacent layer and AlO x barrier. Interfacial oxidation treated on the monolayer thick Co adjacent layer has enhanced perpendicular magnetic anisotropy of the entire Co/Pt multilayer electrodes, enabling sharp transition between well-defined parallel and anti-parallel states at micro-fabricated perpendicular magnetic tunnel junctions of 100 m 2 resistance-area product.

An Overview of Spintronic True Random Number Generator

“…Conversely, the magnetization of the free FM layer can be orientated so that the MTJs are switched between parallel and anti-parallel states to encode information (Figure 1B). There are three main types of physical mechanisms that change the state of MTJ, namely the toggle switching by charge current induced Oersted field [15,16], the spin transfer torque (STT) [17][18][19][20][21], or the spin orbit torque (SOT) by spin current mediated angular momentum transfer [22,23]. Aside from these different switching mechanisms, the structure of MTJ itself also differs in different forms, such as the conventional in-plane magnetized MTJs [24], the perpendicular MTJs (p-MTJ) with magnetizations perpendicular to the film plane [25], and the orthogonal MTJs with inplane free FM layer and perpendicular pinned FM layer [26].…”