Innovative Spin Filtering Techniques Using Insulating Altermagnets

Recent research by Kartik Samanta, Ding-Fu Shao, and Evgeny Y. Tsymbal introduces a novel approach to spintronics through the use of insulating altermagnets. Their paper, titled "Spin filtering with insulating altermagnets," discusses the potential of altermagnetic insulators (AMIs) as efficient spin-filter materials, a concept that has not been extensively explored compared to their metallic counterparts.

The authors analyze the complex band structure of rutile-type altermagnets, specifically focusing on materials such as $MF_2$ (where $M$ represents iron, cobalt, or nickel). They demonstrate that the evanescent states in these AMIs exhibit spin- and momentum-dependent decay rates. This leads to a significant momentum-dependent spin polarization of the tunneling current, which is crucial for the development of advanced spintronic devices.

One of the key findings of the study is the prediction of a sizable tunnel magnetoresistance (TMR) effect in spin-filter magnetic tunnel junctions (SF-MTJs) that incorporate two magnetically decoupled $MF_2$ (001) barrier layers. The researchers estimate a TMR ratio of approximately 150-170% when the Fermi energy is adjusted near the valence band maximum. This suggests that AMIs could serve as viable alternatives to conventional ferromagnetic or ferrimagnetic materials in spintronic applications.

The implications of this research are significant for the future of antiferromagnetic spintronics, potentially leading to the development of next-generation devices that leverage the unique properties of insulating altermagnets. The findings could pave the way for more efficient and advanced technologies in the field of spintronics, which is critical for the evolution of data storage and processing technologies.

For further details, the paper can be accessed at arXiv:2409.00195.