Jul 9 2019
A theoretical-experimental partnership across two FLEET nodes has discovered new magnetic properties inside 2D structures, with stimulating potential for scientists in the evolving domain of “spintronics”.
“We discovered a previously unseen mode of giant magneto-resistance,” FLEET Ph.D. and study co-author Sultan Albarakati (RMIT). (Image credit: FLEET)
Spintronic instruments use a quantum property called “spin”, over and above the electronic charge of conventional electronics. Spintronics, therefore, assure ultra-high speed low-energy electronic devices with considerably enhanced functionality.
The RMIT-UNSW research discovered for the first time ever magnetic properties in devices called vdW hetero-structures composed of several layers of unique, 2D materials. The recent results indicate that vdW spintronics could offer devices more functionality, than the traditional spintronic methods. Additional research could produce devices with major industrial applications.
Background
Two-dimensional (2D) ferromagnetic van-der-Waals (vdW) materials have recently materialized as positive building blocks for a new generation of “spintronic” devices.
When layered with non-magnetic vdW materials, such as topological insulators and/or graphene, vdW hetero-structures can be assembled to deliver otherwise unachievable device structures and performances.
The material examined was 2D Fe3GeTe2 (FGT), a metal proven to exhibit promising ferromagnetic properties for spintronic devices in an earlier FLEET research.
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.
In contrast to the conventional, formerly-known two GMR states (that is, high resistance and low resistance) that occur in thin-film hetero-structures, the scientists also measured anti-symmetric GMR with an extra, distinct intermediate resistance state.
"This reveals that vdW ferromagnetic hetero-structures exhibit substantially different properties from similar structures," says Sultan.
This unexpected result is opposing to formerly held opinions about GMR. It is indicative of different underlying physical mechanisms in vdW hetero-structures, with the potential for better magnetic information storage.
Theoretical calculations show that the three levels of resistance are the outcome of spin-momentum-locking induced spin-polarized current at the graphite/FGT interface.
This work has significant interest for researchers in 2D materials, spintronics, and magnetism. 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.
Cheng Tan, PhD Researcher and Study Co-Author, FLEET