BaMn2P2: highest magnetic ordering temperature 122-pnictide compound

Abstract

We report the growth of high-quality single crystals of ThCr2Si2-type tetragonal BaMn2P2 and investigation of its structural, electrical transport, thermal, and magnetic properties. Our results of basal plane electrical resistivity and heat capacity measurements show that the compound has an insulating ground state with a small band gap. Anisotropic susceptibility χab,c (T ) data infer a collinear local-moment Néel-type antiferromagnetic (AFM) ground state below the ordering temperature TN = 795(15) K, which is highest among all the ThCr2Si2-and CaAl2Si2-type 122-pnictide compounds reported so far suggesting that the strength of magnetic exchange interactions is strongest in this material. The magnetic transition temperatures of BaMn2Pn2 (Pn = P, As, Sb, Bi) compounds exhibit a monotonic decrease with the increase of tetragonal unit cell parameters a and c, suggesting a strong dependence of the strength of the decisive magnetic exchange interactions on the separation between the localized spins residing on the Mn ions. The observed monotonic increase of both χab and χc for T > TN suggests that short-range dynamic quasi-two-dimensional AFM correlations persist above the TN up to the highest temperature of the measurements. The large TN of BaMn2P2 demands for systematic hole-doping studies on this material as similar investigations on related BaMn2As2 with TN = 618 K have led to the discovery of an outstanding ground state where AFM of localized Mn spins and itinerant half-metallic ferromagnetism with Tc ≈ 100 K originating from the doped holes coexist together.