Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals

TL;DR

This study reports the synthesis and characterization of semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals, revealing their antiferromagnetic order, anisotropic magnetic properties, and quasi-two-dimensional magnetic behavior with distinct structural and magnetic transition temperatures.

Contribution

It provides new insights into the magnetic and electronic properties of SrMn2Sb2 and BaMn2Sb2, highlighting their antiferromagnetic order and structural differences compared to related Mn pnictides.

Findings

Both compounds are semiconductors with activation energies of 0.35 eV and 0.16 eV.

SrMn2Sb2 orders antiferromagnetically at 110 K, BaMn2Sb2 at 450 K.

Strong short-range AFM correlations exist above TN up to 900 K.

Abstract

Crystals of SrMn2Sb2 and BaMn2Sb2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity rho, heat capacity Cp, and magnetic susceptibility chi measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn2Sb2 adopts the trigonal CaAl2Si2-type structure whereas BaMn2Sb2 crystallizes in the tetragonal ThCr2Si2-type structure. The rho(T) data indicate semiconducting behaviors for both compounds with activation energies of 0.35 eV for SrMn2Sb2 and 0.16 eV for BaMn2Sb2. The chi(T) and Cp(T) data reveal antiferromagnetic (AFM) ordering at TN = 110 K for SrMn2Sb2 and 450~K for BaMn2Sb2. The anisotropic chi(T < TN) data also show that the ordered moments in SrMn2Sb2 are aligned in the hexagonal ab plane whereas the ordered moments in BaMn2Sb2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn2Sb2 exhibit a continuous metamagnetic transition at low fields 0 < H < 1 T, whereas BaMn2Sb2 exhibits no metamagnetic transitions up to 5.5 T. The chi(T) data for both compounds and the Cp(T) data for SrMn2Sb2 and BaMn2Sb2 indicate strong dynamic short-range AFM correlations above their respective TN up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl2Si2 and ThCr2Si2 crystal structures show that the TN values for the CaAl2Si2-type compounds are much smaller than those for the ThCr2Si2-type materials.