Epitaxial thin films of complex spin injector candidates

Spintronic applications require materials capable of injecting and manipulating spin polarized electrons efficiently. However, the need for increased performance pits a variety of factors against each other. The few complex material systems with higher spin polarization than the state of the art can only be grown epitaxially if they have low lattice mismatch to the few feasible substrate, buffer, or tunnel barrier options. Dislocation defects and spin orbit effects make highly uniform and highly pure films critical. On top of this, efficient spin injection requires the high spin polarization injector to also have low Schmidt conductivity mismatch. Successfully converging every need experimentally in thin films remains a challenge. 

 

In this talk, we will discuss our attempts to employ sputter beam epitaxy to fabricate films on substrates of interest for spin-based devices (Si, SrTiO3).  Candidate materials include spin-gapless semiconductor candidates Mn2CoAl and Ti2CoSi, as well as ternary alloys predicted by our own theoretical surveys to (1) match useful substrates epitaxially and (2) deliver highly spin polarized currents at room temperature. Structural, magnetic, and electrical characterization of the systems explored will highlight lessons learned on epitaxial growth of each explored system.