Unusual Mn-Mn spin coupling in the polar intermetallic compounds CaMn2Sb2 and SrMn2Sb2

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 P3m1, No. 164) with unit cell parameters determined at 120(2) K of a = 4.5204(6) A, c = 7.456(2) A and a = 4.5802(17) A, c = 7.730(5) A 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 at...