Heusler Alloys for Spintronic Devices

In spintronics, magnetic tunnel and giant magnetoresistive junctions have been commonly used for magnetic recording, memories and sensors [1,2]. These junctions typically consist of a CoFeB/MgO/CoFeB trilayer. They satisfy the endurance required for nanometric fabrication and GHz operation. For further improvement in their performance, namely their magnetoresistance ratios, Heusler alloys can be an ideal candidate due to their half-metallicity. Here a Heusler alloy is an ideal vehicle for the development of a new magnetic materials as it covers almost the entire scope of magnetic properties, starting from ferromagnetism and antiferromagnetism to ferrimagnets, spin-gapless semiconductors and topological insulators. Although their crystallinity is important to exhibit these magnetic properties, some alloys can be robust against minor atomic substitution and distortion. This means by forming a crystalline foundation for a Heusler alloy, the corresponding magnetism can be controlled by the compositions, i.e., the total number of electrons contributing transport in a unit cell. 

In this presentation, a range of Heusler alloys and their device applications will be reviewed to demonstrate their importance in spintronics. Recent outcomes using machine learning will also be discussed for the search of new Heusler alloys [3]. 

This work was partially supported by Japan Science and Technology Agency (JST) Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE) program (No. JPMJAP2409), European Commission (EC) European Research Council (ERC) Advanced Grant “Strain-Free All Heusler Alloy Junctions – SAHAJ” (No. 101097475), JSPS Grants-in-Aid (Home-Returning Researcher Development, No. 22K21362) and Ministry of Education, Culture, Sports, Science and Technology (MEXT) Initiative to Establish Next-generation Novel Integrated Circuits Centers (X-nics).