RECENT DEVELOPMENTS IN SPINTRONIC DEVICES

Spintronics is one of the emerging fields for the next-generation nanoelectronic devices that are used to reduce their power consumption, and increase their memory and processing capabilities. Such devices used for the spin degree of freedom of electrons and/or holes, which can also interact with their orbital moments [1]. However, for spintronic devices to meet the ever-increasing demands of the industry, innovation in terms of materials, processes, and circuits are required.

Figure 1. Schematic diagram for major methods to generate a spin-polarised current [2].

Spin-polarised electrons can be generated in non-magnetic (NM) materials using the following methods [2]: spin injection from a ferromagnetic (FM), a magnetic field, an electric field, an electromagnetic wave introduction, a thermal gradient, Zeeman splitting, spin motive force, and mechanical rotation (see Figure 1). One of the most common methods is spin injection from a FM material, e.g., conventional FM metals (Fe, Co, Ni and Gd), half-metallic ferromagnets (HMF) and dilute magnetic semiconductors (DMS), are attached to a NM metal or semiconductors (SC) through an ohmic contact or a tunnel barrier. A stray field at the edge of a FM can also be used to induce a population difference in spin-polarized electrons in a NM material.

B. Dieny et al., have been developed that spintronics can apply in four key areas: magnetic memories, magnetic sensors, radio-frequency and microwave devices, logic and non-Boolean devices [3].

On the other hand of spintronic devices, exploit the spin of electrons to generate and control charge currents, and to interconvert electrical and magnetic signals. By combining processing, storage, sensing, and logic within a single integrated platform, spintronics could complement and, in some cases, outperform semiconductor-based electronics, offering advantages in terms of scaling, power consumption, and data processing speed.

Figure 2. Typical magnetic length scales and the development of magnetic storage devices [2].

In this field, already established many large-scale commercial applications such as Giant magnetoresistance (GMR)-based spin valves and magnetic tunnel junctions (MTJs) have been used as magnetic field sensors in tape and hard disk drive read heads, as position or proximity sensors in cars, automated industrial tools, and biomedical devices. The typical length scales of magnetic devices and systems are listed in Figure 2.

Therefore researchers from this field need to concentrate on these for future developments:

The current and future capabilities of spintronics to the broader electronics community.
To encourage the spintronics community to focus on, and think about it for applications.
The ultimate goal and being a help to translate basic research into industrial technologies and economic gains.
Spintronic devices were optimized for low-temperature operation for quantum engineering or large scale computers.

In particular, the following items should be considered for further improvements or new directions in spintronic device applications from Ref. [1]:

Low power read-out using spin–orbit phenomena rather than tunnel magneto resistance.
Innovative circuits architecture taking full advantage of spintronic phenomena, materials and devices (e.g., in memory computing, normally-off/instant-on architecture).
Unconventional computing using spintronic devices (e.g., stochasticcomputing).
Innovative magnetic field sensors with increased sensitivity, reduced temperature dependence, or broader field dynamics for all kinds of applications from position encoders to medical diagnosis or HDD read-heads.
Coupling of photonics and nanomagnetism/spintronics to the development of optical interconnects in electronics and all optical writing in storage technology.
3D spintronic embodiments for high-density memory and storage devices.
Energy harvesting from thermal gradients via spincaloritronics or electromagnetic radiations using spin-diodes.
Development of artificial neurons and synpases for artificial intelligence based on spintronic devices.
Spintronic devices optimized for low-temperature operation for quantum engineering or large scale computers.

References

A. Hirohata et al., J. Mag. Magn. Mat. 509, 166711 (2020).
A. Hirohata, K. Takanashi, J. Phys. D: Appl. Phys. 47, 193001 (2014).
B. Dieny et al., Nature Electronics, 3, 446 (2020).

Blog Written By

Dr. A. S. Ganeshraja

Assistant Professor

National College, Tiruchirappalli

Tamil Nadu, India

Editors

Dr. K. Rajkumar

Dr. S. Chandrasekar

Reviewers

Dr. Y. Sasikumar

Dr. S. Thirumurugan

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