Collaboration Unlocks New Magnetic Properties for Future, Faster, Low-Energy Spintronics


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A theoretical–experimental collaboration across two FLEET nodes has discovered new magnetic properties within 2D structures, with exciting potential for researchers in the emerging field of ‘spintronics.’

Spintronic devices use a quantum property known as ‘spin’ in addition to the electronic charge of conventional electronics. Spintronics thus promise ultra-high speed low-energy electronic devices with significantly enhanced functionality.

A single ‘bit’ of a conventional device can take two states: represented as 0 and 1. The computing power of conventional electronics thus increases by 2 to the power of the number of bits (2n). One bit: two states, two bits = four states, three bits = eight states, a thousand bits = 10300 states.

In comparison, a single ‘bit’ of a spintronic device has four states: 0-spin up, 0-spin down, 1-spin up, 1-spin down. Its power thus increases by four to the power of the number of bits (4n). One bit: four states, two bits = 16 states, three bits = 64 states, a thousand bits = 10600 states.

The RMIT–UNSW study discovered never-before-seen magnetic properties in devices known as vdW hetero-structures comprising several layers of novel, 2D materials.

The latest results show that vdW spintronics could provide devices with more functionality, comparing with the traditional spintronic approaches. Further research could generate devices with significant industrial applications.

Background

Two-dimensional (2D) ferromagnetic van-der-Waals (vdW) materials have recently emerged as effective building blocks for a new generation of ‘spintronic’ devices. When layered with non-magnetic vdW materials, such as graphene and/or topological insulators, vdW hetero-structures can be assembled to provide otherwise unattainable device structures and functionalities.

The material studied was 2D Fe3GeTe2 (FGT), a metal found to display promising ferromagnetic properties for spintronic devices in a previous FLEET study.

Surprising Discoveries

“We discovered a previously unseen mode of giant magneto-resistance (GMR) in the material, says FLEET PhD and study co-author Sultan Albarakati.

Unlike the conventional, previously-known two GMR states (ie, high resistance and low resistance) that occur in thin-film hetero-structures, the researchers also measured antisymmetric GMR with an additional, distinct intermediate resistance state.

“This reveals that vdW ferromagnetic hetero-structures exhibit substantially different properties from similar structures,” says Sultan.

This surprising result is contrary to previously held beliefs regarding GMR. It is suggestive of different underlying physical mechanisms in vdW hetero-structures, with potential for improved magnetic information storage.

Theoretical calculations indicate that the three levels of resistance are the result of spin-momentum-locking induced spin-polarised current at the graphite/FGT interface.

“This work has significant interest for researchers in 2D materials, spintronics, and magnetism,” says co-author FLEET PhD Cheng Tan. “It means that ‘traditional’ tunnelling magnetoresistance devices, spin-orbit torque devices and spin transistors may reward re-investigated using similar vdW hetero-structures to reveal similarly surprising characteristics.”

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