Magnetic structure of the S = ½ staircase kagome lattice PbCu3TeO7

Abstract

The crystal and magnetic structure characterization of geometrically distorted PbCu3TeO7 with S=1/2 Cu2+ spins forming a staircase kagome lattice was investigated using x-ray and neutron diffraction on a powder sample. The distorted kagome lattice of antiferromagnet PbCu3TeO7 exhibits a quasi-two-dimensional spin network. The x-ray diffraction data show that PbCu3TeO7 crystallizes in the orthorhombic system in the space group Pnma (No. 62). The lattice parameters a = 10.488(1) Å, b = 6.353(1) Å, and c = 8.814(2) Å. Our temperature-dependent x-ray diffraction data show that there is no structure phase transition between 12 and 298 K. From our powder neutron diffraction data at 2 K, we observed two distinct magnetic Bragg peaks at low angles, confirming the magnetic transition to the ordered state at low temperatures. In previous work, the ordering vector for the magnetic structure was determined using simulations to be (0,1/3,0). However, in this work, we found that based on the neutron diffraction data the ordering vector is in fact (0,1/3,1/3). The magnetic structure of PbCu3TeO7 exhibiting an antiferromagnet with noncollinear spin order is proposed.