Giant magnetoresistance in BaMn₂Pn₂ (Pn = As, Sb, Bi)

We report our discovery of a new kind of giant magnetoresistance (GMR) in the family of BaMn₂Pn₂ antiferromagnets, where Pn stands for As, Sb, and Bi [1, 2]. BaMn₂Pn₂’s are intriguing materials hosting a magnetic hexadecapole ordering that preserves the parity-time symmetry even though both time and space inversion are broken [3]. The hexadecapole ordering microscopically stems from symmetry-preserved spin-dependent d-p hybridization that governs the low energetic excitations and therefore promises exotic transport properties. Here we describe a new GMR in BaMn₂Pn₂’s with the following features [1,2]: (1) the magnitudes of the unique negative GMR are larger than 98 %, being comparable with those of other exotic GMR systems, (2) GMR exhibits a very unusual angular under the rotation of magnetic fields, (3) GMR is band selective in sign, showing negative and positive signs for hole- and electron-like carriers, respectively. These properties are incompatible to any known mechanism of magnetoresistance and call for new explanations.
[1] K. K. Huynh et al., submitted (2018)
[2] T. Ogasawara et al.. submitted (2018)
[3] H. Watanabe et al., PRB 96 064432 (2017)