CMOS-compatible low magnetization Heusler compounds enable fast switching in MTJ

Magnetic random-access memories (MRAM) utilize magnetic tunnel junctions (MTJ) as their memory elements. Those components are typically made from ferromagnetic materials such as CoFeB which demonstrate high magnetization, ultimately limiting their speed due to spin-transfer angular momentum conservation.

To address this issue, a team of researchers from IBM took advantage of a very specific family of materials: the Heusler compounds. Ferrimagnetic binary Heusler compounds have very low and weakly temperature-dependent magnetization, making them ideal candidate for high-speed memory applications.

Left: Bright-field transmission electron microscopy cross-sectional image of a Mn₃Ge-free-layer MTJ device with a diameter of ~36 nm. Right: schematic of the MTJ film stack. Credit: IBM Research—Almaden, San Jose.

Thanks to the very low saturation magnetization of the Mn₃Ge Heusler ferrimagnet (which is about 6 times lower than ferromagnetic CoFeB-based MTJs), they were able to reach a pulse write length of 0.5 ns using switching current density as small as 10 MA.s^-1. One crucial point of this device is its CMOS compatibility, indeed these Mn₃Ge-based MTJs are grown on amorphous SiO_x substrate and are thermally stable above 400°C.

Original article: https://doi.org/10.1038/s41565-024-01827-7