Researchers double room temperature tunnel magnetoresistance ratios of Fe/MgO/Fe
Researchers double room temperature tunnel magnetoresistance ratios of Fe/MgO/Fe lead image
Spintronics, as opposed to electronics, aims to utilize the intrinsic spin of the electron and its magnetic moment in addition to its charge, for the advancement of next-gen computing devices. One of the most desirable properties for spintronic materials is to have a large tunnel magnetoresistance (TMR) ratio at room temperature. However, although giant TMR ratios have been predicted in materials with tunnel junction structures, the values yielded in experiments have generally been much smaller.
Scheike et al. synthesized and measured an iron/magnesium oxide/iron tri-layer with a TMR ratio over 400 percent at room temperature and much closer to its theoretical predicted value at low temperature.
“The spintronic device community believed that TMR ratios would not exceed 400 percent in realistic spin-valve-type junctions,” said author Hiroaki Sukegawa. “However, we demonstrate the present large TMR ratios that break this preconceived idea.”
To improve the TMR ratio, the researchers developed high-quality films to create the tri-layer. To maximize performance, the team examined processes such as ultra-thin layer insertion and annealing to finetune the interfaces where the layers made contact.
“Imagine you want to build a wall with several layers of bricks. To make the wall perfect you want every brick layer and every interface, the mortar, to be as flat and well-aligned as possible,” said Sukegawa. “We made each brick and interface flat to suppress formation of defects and cracks.”
The researchers hope their work is a step toward new spintronic device architectures.
“We are convinced that new devices with much larger TMR ratios can be developed using the knowledge of this work,” said Sukegawa.
Source: “Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions,” by Thomas Scheike, Qingyi Xiang, Zhenchao Wen, Hiroaki Sukegawa, Tadakatsu Ohkubo, Kazuhiro Hono, and Seiji Mitani, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0037972 .
