Spin correlations and exchange in square-lattice frustrated ferromagnets

M. SKOULATOS; J. P. GOFF; C. GEIBEL; E. E. KAUL; R. NATH; N. SHANNON; B. SCHMIDT; A. P. MURANI; P. P. DEEN; M. ENDERLE; A. R. WILDES

EUROPHYSICS LETTERS

EPL ASSOCIATION

Año: 2009 vol. 88 p. 570051 - 570055

0295-5075

The J1-J2 model on a square lattice exhibits a rich variety of different forms of magnetic order that depend sensitively on the ratio of exchange constants J2/J1. We use bulk magnetometry and polarized neutron scattering to determine J1 and J2 unambiguously for two materials in a new family of vanadium phosphates, Pb2VO(PO4)2 and SrZnVO(PO4)2, and we find that they have ferromagnetic J1. The ordered moment in the collinear antiferromagnetic ground state is reduced, and the diffuse magnetic scattering is enhanced, as the predicted bond-nematic region of the phase diagram is approached.