Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 10: Magnetic Materials
MA 10.3: Vortrag
Montag, 25. Februar 2008, 15:45–16:00, H 1028
Magnetic and thermodynamic properties of the frustrated ferromagnetic square lattice BaCdVO(PO4)2 — •Ramesh Nath1, A. A. Tsirlin1,2, H. Rosner1, and C. Geibel1 — 1MPI CPfS, Nöthnitzer Str. 40, 01187 Dresden, Germany — 2Department of Chemistry, Moscow State University, 119992, Moscow, Russia
The spin 1/2 Heisenberg model on a square lattice with antiferromagnetic (AF) nearest J1 and next nearest neighbour J2 interactions has been a focus of extensive theoretical research for the last decades. Experimentally, only a limited number of compounds of this model have been realized so far. Very recently new materials, (Pb2,SrZn)VO(PO4)2 were found to be square lattice systems with mixed ferromagnetic (F) and AF exchange interactions which stimulated the theoretical research to extend the phase diagram including F J1 and J2. In this context, we would like to present a new compound BaCdVO(PO4)2, which is isostructural to SrZnVO(PO4)2 and more exciting from the magnetic point of view. Magnetization and specific heat measurements on powder sample evidence that BaCdVO(PO4)2 is a S=1/2 frustrated square lattice with F J1 and AF J2. The absolute values were estimated to be J1≃−3.6 K and J2≃3.2 K which are consistent with a strongly reduced (or vanishing) Curie temperature θCW. BaCdVO(PO4)2 undergoes a magnetic ordering at about 1 K, likely towards a columnar antiferromagnetic state as expected from the ratio J2/J1≃−0.85 and the saturation field Bsat ≃ 4.5 T. This ratio, places the system more close to the quantum critical regime in the phase diagram than previously reported compounds.