Magnetic order in acentric Pb2MnO4

Abstract

The low temperature magnetic properties of Pb₂MnO₄, which crystallises in an acentric but non-polar space group (P2₁c) that allows piezoelectricity, have been investigated. Magnetisation measurements reveal a sharp transition to an antiferromagnetically ordered state at 18 K. Powder neutron diffraction at 1.5 K shows the spin structure to have a (000) propagation vector with Mn⁴⁺ moments of 2.74(2) μ_B lying in the ab plane. The magnetic symmetry group is P′2₁c′ which permits piezomagnetism (stress-induced weak ferromagnetism). Possible ‘multipiezo’ properties of coupled magnetisation and electrical polarisation under mechanical stress in Pb₂MnO₄ are briefly discussed.