Spin correlations and exchange in square-lattice frustrated ferromagnetsM. Skoulatos1, J. P. Goff2, C. Geibel3, E. E. Kaul3, R. Nath3, N. Shannon4, B. Schmidt3, A. P. Murani5, P. P. Deen5, M. Enderle5 and A. R. Wildes5
1 Helmholtz Centre Berlin for Materials and Energy - Hahn-Meitner-Platz 1, 14109 Berlin, Germany, EU
2 Department of Physics, Royal Holloway, University of London - Egham, Surrey TW20 0EX, UK, EU
3 Max-Planck Institute for Chemical Physics of Solids - Nöthnitzer Str. 40, Dresden 01187, Germany, EU
4 H.H. Wills Physics Laboratory, University of Bristol - Bristol BS8 1TL, UK, EU
5 Institut Laue-Langevin - BP 156X, 38042 Grenoble Cedex, France, EU
received 14 October 2009; accepted in final form 12 November 2009; published December 2009
published online 11 December 2009
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.
75.30.Et - Exchange and superexchange interactions.
75.40.Cx - Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.).
75.40.Gb - Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.).
© EPLA 2009