Negative and positive magnetoresistance in the itinerant antiferromagnet BaMn2Pn2 (Pn = P, As, Sb, and Bi)

We report the discovery of a large-magnetoresistance (LMR) phenomenon in a family of BaMn2Pn2 antiferromagnets (Pn = P, As, Sb, and Bi) with parity-time symmetry. The resistivities of these materials are reduced by 60 times in magnetic fields H, thus yielding a LMR of about −98%. The LMR changes systematically along with the Pn elements, hinting that its origin is the spin-orbit coupling and/or d−p orbital hybridization. A positive MR component emerging on top of the negative LMR at low temperatures suggests an orbital-sensitive magnetotransport as H suppresses the conduction of the electronlike carriers in the d-like band but enhances that of holelike ones in the d−p hybridized band. The anisotropy of the LMR reveals that the electrical conductivity is extremely sensitive to the minute changes in the direction of the antiferromagnetic moments induced by the parity-time symmetry-breaking H, which is perpendicular to the antiferromagnetic spin-ordered direction. We attribute the observed LMR to the nontrivial low-energy bands of BaMn2Pn2 antiferromagnets, which are governed by the parity-time symmetry.