Abstract

This literature review provides a thorough examination of the fast-paced field of spintronics, focusing on the critical role of Spin-Orbit Torque (SOT) in novel heterostructures. The key objective is to integrate key findings from a broad spectrum of contemporary investigations concerning Heavy-Metal/Ferromagnet bilayers. We delve into the underlying physics, laboratory breakthroughs, and potential applications identified in the current academic discourse. This review attempts to establish a useful resource for academics engaged in this fascinating area of nanotechnology.

1. Introduction

The search for low-power memory devices has fueled intensive study into spin-based electronics, which utilizes the electron's spin degree of freedom in alongside its charge. Conventional spintronic elements, such as Magnetic Tunnel Junctions (MTJs) memory cells, utilize spin-polarized currents and external fields for operation. However, the need for faster, denser, and energy-frugal performance has stimulated the search of alternative control techniques, namely Spin Caloritronics. These effects allow the effective manipulation of magnetization with thermal gradients in specially engineered multilayers, establishing them as highly compelling for use in high-density logic technologies.

2. Fundamental Principles and Mechanisms

The physical basis of Spin Caloritronics lies in the complex interaction between spin, electronic structure, and heat in nanoscale systems. In the context of Spin-Orbit Torque, the main source is the Spin-Hall Effect (SHE). The SHE converts a charge current in a heavy metal (e.g., Pt) into a perpendicular spin current, which then exerts a moment on the neighboring magnetic layer, potentially reorienting its polarization. Similarly, Spin Caloritronics relies on the change of electron densities via the use of an charge accumulation at an junction, thereby lowering the energy barrier required for reversal. On the other hand, Ignou MBA Project Spin Caloritronics investigates the interconversion between heat currents and temperature differences, opening up pathways for waste heat recycling and unique detection modalities.

3. Review of Key Material Systems

The effectiveness of SOT switching is profoundly dependent on the choice of materials and the cleanliness of their junctions. This review examines three key material systems:

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• Heavy-Metal/Ferromagnet Bilayers: These are the most studied system for studying SOT. Elements like Pt act as efficient spin current sources, while Fe acts as the ferromagnetic layer. Research has centered on optimizing parameters such as layer thicknesses to maximize the damping-like torque.
  
• Complex Oxide Interfaces: These heterostructures integrate magnetic and polar properties in a composite system. The primary interest for electric-field control is the strong coupling between ferroelectricity and magnetism, that can lead to