Unusual Mn−Mn Spin Coupling in the Polar Intermetallic Compounds CaMn2Sb2 and SrMn2Sb2

Abstract

Large single-crystals of two polar intermetallic phases, CaMn₂Sb₂ and SrMn₂Sb₂, have been grown using In or Sn as metal fluxes and characterized by single-crystal X-ray diffraction. The two compounds are isostructural and crystallize with the CaAl₂Si₂ structure (space group P3̄m1, No. 164) with unit cell parameters determined at 120(2) K of a = 4.5204(6) Å, c = 7.456(2) Å and a = 4.5802(17) Å, c = 7.730(5) Å for CaMn₂Sb₂ and SrMn₂Sb₂, respectively. Temperature- and field-dependent dc- and ac-magnetization measurements suggest complex magnetic ordering of the Mn moments below ca. 250 and 35 K for CaMn₂Sb₂ and below ca. 265 K for SrMn₂Sb₂. Resistivity measurements reveal metallic-like temperature dependence with ρ₂₉₀ = 40 mΩ cm for CaMn₂Sb₂ and ρ₂₉₀ = 100 mΩ cm for SrMn₂Sb₂ with negligible magnetoresistance at 5 K in applied magnetic fields up to 10 kOe. Spin-polarized DFT electronic structure calculations confirm the metallic-like properties and provide further evidence for a magnetic structure where Mn atoms form two magnetic sublattices with ferromagnetic coupling within them and strong antiferromagnetic coupling between them.