Giant magnetoresistive effects in antiferomagnetic semiconductors BaMn₂Pn₂ (Pn = As, Sb, Bi)

In this talk, we report the intriguing giant negative magnetoresistive effects observed in BaMn₂Pn₂ compounds, in which Pn stands for the pnictogens As, Sb, and Bi. These materials adopts identical (122) crystallographic and G-type antiferromagnetic structures and can be very interesting from the view point of symmetry. Here the magnetic point group 4’/m’mm’ directly suggests the existence of a diagonal dissipative magnetoelectric effect confined in the ab plane of the crystals. Importantly, by changing the Pn elements, both spin-orbit coupling and pd hybridization can be tuned without disturbing the symmetry.
We will describe the first systematic observations on the magnetotransport properties of BaMn₂Pn₂ compounds under a wide range of magnetic fields (B) and temperatures (T). All three compounds show very large negative magnetoresistance (MR) with complex dependencies on B and T. When Pn elements were changed from As to Bi, the observed MR changed systematically in both its magnitude and B-dependence. In the extreme B regime, the MR of BaMn₂Bi₂ becomes the largest among the BaMn₂Pn₂’s in the smallest B-range.