Towards fabrication of tetragonally distorted Fe2PtGe Heusler alloy thin films with large perpendicular magnetic anisotropy for spintronic applications

Tetragonally distorted Heusler alloys are the promising class of materials for developing efficient spintronic devices such as magnetic tunnel junctions used for spin-transfer torque magnetic random-access memory due to their potentially large perpendicular magnetic anisotropy (PMA), high spin polarization, high Curie temperature, and small lattice mismatch with MgO tunnel barriers. Motivated by the previous theoretical prediction [ J. Phys. D: Appl. Phys. 50 , 095002 (2017)], we aim to experimentally demonstrate large PMA in tetragonally distorted Fe 2 PtGe Heusler alloy thin films on MgO(001) substrates. Although a relatively large PMA is obtained, microstructure analysis reveals the rejection of Ge atoms from the parent matrix of Fe 2 PtGe and the separation into Ge-poor and Ge-rich L 1 0 -ordered FePt regions by heating in the film deposition process. Our negative but preliminary results would provide experimental scientists useful knowledge for realizing theoretically-predicted tetragonally distorted Heusler alloys in the future.