Spin correlations in the frustrated square lattice Pb2VO(PO4)2

SKOULATOS, M.; GOFF, J. P.; SHANNON, N.; KAUL, E. E.; GEIBEL, C.; MURANI, A. P.; ENDERLE, M.; WILDES, A. R.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

Elsevier

Año: 2007 vol. 310 p. 1257 - 1259

0304-8853

The new frustrated square-lattice system, Pb2VO(PO4)2, has been investigated using polarised neutron scattering. From these studies, made on powdered samples, we have determined the nature of the exchange interactions and the magnetic ordering for this novel quantum magnet. Quantum order from disorder occurs at low temperature, and the ground state observed below the Ne´ el temperature T_N~3.7K is a collinear antiferromagnet. At room temperature there are no magnetic correlations and it is possible to model the scattering with the V4+ magnetic form factor. However, at T~20 K, a temperature well into the paramagnetic phase, magneticcorrelations are observed, and these spin correlations have been modelled using a high-temperature series expansion. Ferromagnetic nearest-neighbour exchange J1~-2K and antiferromagnetic next-nearest-neighbour exchange J2~6.5K are obtained, and this is ofparticular interest theoretically, since it corresponds to a new region of the J1–J2 phase diagram.