The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spin-polarized currents can be generated several ways: by passing an unpolarized current through a ferromagnetic contact, using the spin-Hall effect, by ballistic and hot electron injection, by using spin-polarized materials such as half-metals, or using a spin filter material. Half metals and spin filter (SF) materials are especially suitable for spin injectors that are based on magnetic tunnel junctions (MTJs). However, a spin injector using a spin filter material is simpler, as it does not require magnetic electrodes.
Illustration of the DOS for majority and minority spin states, with various band gaps.
Spin gapless semiconductors (SGS) and spin filter materials (SFM) uniquely merge the properties of diversely gapped semiconductors and high Curie temperature magnetism. This remarkable combination of properties in Heusler compounds could have advantages for spin-transport in electronic/magnetic devices and quantum information processing. New functionalities are poised to take advantage of several novel and valuable properties, especially at room temperature. Some of the unique properties are:
(1) half-metallic high spin polarization (100 %);
(2) carrier flexibility allowing for generation of spin-polarized holes;
(3) voltage-tunable spin polarization with n-type/p-type switching;
(4) spin-polarized ferrimagnets with zero moment;
(5) spin filters.
A number of these fascinating Heusler materials have been grown in bulk form, but the synthesis of high-quality thin films necessary for devices is difficult.
Magnetic moment of the antiferromagnetic gapless semiconductor V3Al at 2T, showing a very low moment and a peak at the Neel temperature TN=600 K. (inset) m(H) showing linear-in-H dependence and temperature independence. M.E. Jamer, et al. Phys. Rev. B 91, 094409 (2015)."