Electronic and magnetic properties of CrVTiAl room temperature spin filter films*

Spin filter materials (SFMs) are magnetic semiconductors with different bandgaps for each spin direction, which provide a promising alternative to present methods of spin-current generation. When used as a tunneling barrier between nonmagnetic metallic contacts, the SFM can block one spin direction to produce a highly spin-polarized current. Traditional SFMs have low magnetic transition temperatures making them unsuitable for room temperature applications. Their large magnetic moments produce strong fringing fields that would be detrimental to nearby magnetic elements in devices. The Heusler compound CrVTiAl is a promising new SFM candidate due to its predicted high Curie temperature and near-zero magnetic moment. CrVTiAl thin films have been synthesized on various substrates by magnetron sputtering and subsequently annealed. The magnetic moment is confirmed to be small and is nearly temperature independent, consistent with the behavior of a compensated ferrimagnet. The temperature-dependent resistivity shows small-bandgap semiconducting behavior. The existence of semiconducting behavior is in accordance with our DFT calculations and could lead to the realization of a room temperature spin filter device.