EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In spintronics, magnetic tunnel and giant magnetoresistive junctions have been used for read heads for data storage, magnetic memories and sensors [1]. Current technology uses CoFeB as a ferromagnetic layer with a face-centred cubic crystalline structure induced by seed layers with platinum group metals, and a MgO tunnel barrier. These satisfy high temperature endurance (typically 1 min. at 270ºC for memories and 3,000 h at 175ºC for sensors) and corrosion resistance. In order to achieve these requirements, Heusler alloys holds great potential with exhibiting only one spin channel at the Fermi level [2].

Machine learning has been used for the search of new magnetic materials. As an example, NiCrMnSi (NCMS) alloy has been predicted to be ferromagnetic in experimental and theoretical studies [3],[4]. In this study, we investigated structural and magnetic properties on NiCrMnSi and the other alloys. NCMS samples were sputtered using ultrahigh vacuum magnetron sputtering, consisting of MgO(001) substrate/NCMS (100)/Ta (3) (thickness in nm). The NCMS samples were in situ annealed at 500ºC and 700ºC before the Ta layer was deposited. Additional alternative alloys and barriers have also been investigated in a similar manner and characterised in a junction form. We will present the details of our recent achievements in our presentation.

This work was partially supported by JST-CREST (No. JPMJCR17J5), EU-EIT-IRTC Business and EPSRC (EP/V007211/1).

[1] A. Hirohata et al., J. Magn. Magn. Mater. 509, 166711 (2020).
[2] C. Felser and A. Hirohata, Heusler Alloys (Springer, Berlin, Germany, 2016).
[3] V. D. Buchelnikov et al., J. Magn. Magn. Mater. 459, 78 (2018).
[4] Y. Jin et al., Appl. Phys. Lett. 109, 142410 (2016).