Square-lattice magnetism of diaboleite Pb2Cu(OH)4Cl2

We report on the quasi-two-dimensional magnetism of the natural mineral diaboleite Pb2Cu(OH)(4)Cl-2 with a tetragonal crystal structure, which is closely related to that of the frustrated spin-1/2 magnet PbVO3. Magnetic susceptibility of diaboleite is well described by a Heisenberg spin model on a diluted square lattice with the nearest-neighbor exchange of J similar or equal to 35 K and about 5% of nonmagnetic impurities. The dilution of the spin lattice reflects the formation of Cu vacancies that are tolerated by the crystal structure of diaboleite. The weak coupling between the magnetic planes triggers the long-range antiferromagnetic order below T-N similar or equal to 11 K. No evidence of magnetic frustration is found. We also analyze the signatures of the long-range order in heat-capacity data, and discuss the capability of identifying magnetic transitions with heat-capacity measurements. DOI: 10.1103/PhysRevB.87.064404