Journal
JOURNAL OF PHYSICS-CONDENSED MATTER
Volume 29, Issue 7, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1361-648X/aa50e0
Keywords
half metals; Heusler materials; spintronics
Categories
Funding
- National Science Foundation (NSF) through the summer programs of the Nebraska Materials Research Science and Engineering Center (MRSEC) [DMR-1420645]
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A high degree of spin polarization in electron transport is one of the most sought-after properties of a material which can be used in spintronics-an emerging technology utilizing a spin degree of freedom in electronic devices. An ideal candidate to exhibit highly spin-polarized current would be a room temperature half-metal, a material which behaves as an insulator for one spin channel and as a conductor for the other spin channel. In this paper, we explore a semi-Heusler compound, IrMnSb, which has been reported to exhibit pressure induced half-metallic transition. We confirm that the bulk IrMnSb is a spin-polarized metal, with dominant contribution to electronic states at the Fermi energy from majority-spin electrons. Application of a uniform pressure shifts the Fermi level into the minority-spin energy gap, thus demonstrating pressure induced half-metallic transition. This behavior is explained by the reduction of the exchange splitting of the spin bands consistent with the Stoner model for itinerant magnetism. We find that the half-metallic transition is suppressed when instead of uniform pressure the bulk IrMnSb is exposed to biaxial strain. This suppression of half-metallicity is driven by the epitaxial strain induced tetragonal distortion, which lifts the degeneracy of the Mn 3d t(2g) and e(g) orbitals and reduces the minority-spin band gap under compressive strain, thus preventing half-metallic transition. Our calculations also indicate that in thin film geometry, surface states emerge in the minority-spin band gap, which has detrimental for practical applications impact on the spin polarization of IrMnSb.
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