Antiferromagnetism and geometric frustration in tetrahedral lattice hydroxyhalidesM2(OH)3X

Abstract

A systematic study of magnetic susceptibility measurementsis carried out on distorted tetrahedral lattice hydroxyhalidesFe2(OH)3Cl,Mn2(OH)3Cl,Mn2(OH)3Br,and Co2(OH)3Br, following our recent finding of coexisting antiferromagnetic order and disorder inCu2(OH)3Cl (clinoatacamite). These transition metal hydroxyhalides are found to undergo antiferromagnetic transitions,at TN = 14 K forFe2(OH)3Cl, at two successivetransitions of TN1 = 3.4 K and TN2 = 2.7 K for Mn2(OH)3Cl, at TN1 = 3.3 Kand TN2 = 2.4 Kfor Mn2(OH)3Br,and at TN = 5 K for Co2(OH)3Br, respectively. All hydroxychlorides show coexisting glassiness below the magnetictransitions; meanwhile, the glassiness is not found in the hydroxybromides. The distortedtetrahedral lattice for the magnetic ions consists of stacked layers of triangularlattice planes and Kagome lattice planes, with the magnetic ions on the Kagomelattice planes being bonded by the halogen ions. The contrasting behaviours inMn2(OH)3Cl and Mn2(OH)3Br suggest that the glassiness arises from competing magnetic interactions in the tetrahedron,specifically on the Kagome lattice planes.