Abstract

This paper offers a detailed examination of the dynamic field of magnetoelectronics, focusing on the pivotal role of Spin-Orbit Torque (SOT) in cutting-edge material systems. The main purpose is to synthesize key findings from a broad range of recently published studies concerning Multiferroic junctions. We explore the underlying physics, Ignou Project advancements in experimentation, and potential applications identified in the present academic discourse. This review attempts to establish a valuable resource for scientists working in this intriguing field of materials science.

1. Introduction

The search for next-generation electronic devices has driven significant investigation into spin-based electronics, which exploits the electron's spin attribute in alongside its charge. Conventional spintronic devices, such as Giant Magnetoresistance (GMR) memory cells, depend on spin-polarized electron flow and applied fields for functioning. However, the requirement for more efficient, scalable, and energy-frugal operation has prompted the exploration of alternative switching methods, such as Spin Caloritronics. These phenomena enable the effective manipulation of spins via thermal gradients in nanoscale thin films, rendering them particularly promising for applications in non-volatile memory devices.

2. Fundamental Principles and Mechanisms

The physical basis of Spin Caloritronics lies in the complex interaction between magnetism, orbit, and charges in nanoscale devices. In the case of Spin-Orbit Torque, the main driver is the Spin-Hall Effect (SHE). The REE converts a charge current in a material with strong spin-orbit coupling (e.g., W) into a perpendicular flow of angular momentum, which then exerts a torque on the adjacent ferromagnetic layer, effectively reorienting its polarization. Similarly, Spin Caloritronics relies on the alteration of interface properties via the application of an voltage pulse at an junction, thereby changing the energy barrier required for reversal. On the other hand, the spin Seebeck effect explores the interconversion between spin currents and thermal gradients, presenting pathways for waste heat recycling and new sensing modalities.

3. Review of Key Material Systems

The effectiveness of thermal spin manipulation is extremely contingent on the selection of constituent layers and the quality of their interfaces. This review highlights three key material systems:

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• Heavy-Metal/Ferromagnet Bilayers: This is the most studied system for studying SOT. Elements like Ta function as strong spin current generators, while Fe is the switchable layer. Work has centered on optimizing parameters such as interface transparency to increase the damping-like torque.
  
• Multiferroic Interfaces: These structures combine ferromagnetic and ferroelectric order in a single system. The main interest for VCMA is the significant interaction between ferroelectricity and magnetic anisotropy, which can result in