First principles design of Ohmic spin diodes based on quaternary Heusler compounds

The Ohmic spin diode (OSD) is a recent concept in spintronics, which is based on half-metallic magnets and spin-gapless semiconductors (SGSs). Quaternary Heusler compounds offer a unique platform to realize the OSD for room temperature applications as these materials possess very high Curie temperatures as well as half-metallic and spin-gapless semiconducting behavior within the same family. Using state-of-the-art first-principles calculations combined with the nonequilibrium Green's function method, we design four different OSDs based on half-metallic and spin-gapless semiconducting quaternary Heusler compounds. All four OSDs exhibit linear current–voltage (I–V) characteristics with zero threshold voltage V_T. We show that these OSDs possess a small leakage current, which stems from the overlap of the conduction and valence band edges of opposite spin channels around the Fermi level in the SGS electrodes. The obtained on/off current ratios vary between 30 and 10⁵. Our results can pave the way for the experimental fabrication of the OSDs within the family of ordered quaternary Heusler compounds.