[Prof. Hyun-Woo Lee] Gigantic Current Control of Coercive Field and Ma…

Caption: (a) Atomic structure of Fe3GeTe2.  (b) Schematic diagram of the current-induced spin-orbit torque effect on the coercive field of Fe3GeTe2. (c) Comparison between the spin-orbit torque magnitude per current density for various materials.

[Prof. Hyun-Woo Lee] Gigantic Current Control of Coercive Field and Magnetic Memory Based on Nanometer‐Thin Ferromagnetic van der Waals Fe3GeTe2

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Researchers at Pohang University of Science and Technology (POSTECH) and Seoul National University in South Korea have demonstrated a new way to enhance the energy efficiency of a non-volatile magnetic memory device called SOT-MRAM (spin-orbit torque magnetic RAM). Published in Advanced Materials, this finding opens up a new window of exciting opportunities for future energy-efficient magnetic memories based on spintronics.

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In the SOT-MRAM, magnetization directions of tiny magnets store information and writing amounts to changing the magnetization directions to desired directions. The magnetization direction change is achieved by a special physics phenomenon called SOT that modifies the magnetization direction when a current is applied. To enhance the energy efficiency, soft magnets are ideal material choice for the tiny magnets since their magnetization directions can be easily alterned by a small current. Soft magnets are bad choice for the safe storage of information since their magnetization direction may be altered even when not intended – due to thermal noise or other noise. For this reason, most attempts to build the SOT-MRAM adopt hard magnets, because they magnetize very strongly and their magnetization direction is not easily altered by noise. But this material choice inevitably makes the energy efficiency of the SOT-MRAM poor.

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A joint research team led by Professor Hyun-Woo Lee in the Department of Physics at POSTECH and Professor Je-Geun Park in the Department of Physics at Seoul National University demonstrated a way to enhance the energy efficiency without sacrificing the demand for safe storage. They reported that ultrathin iron germanium telluride (Fe3GeTe2, FGT) – a ferromagnetic material with special geometrical symmetry and quantum properties – switches from a hard magnet to a soft magnet when a small current is applied. Thus when information writing is not intended, the material remains a hard magnet, which is good for the safe storage, and only when writing is intended, the material switches to a soft magnet, allowing for enhanced energy efficiency. 
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