Regensburg 2002 – wissenschaftliches Programm
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MA: Magnetismus
MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111
MA 10.107: Poster
Dienstag, 12. März 2002, 15:00–19:00, Bereich A
Interplay between structure and magnetism in (Cu,Zn)2V2O7 — •K.-Y. Choi1, J. Pommer1, A. Ionescu1, P. Lemmens1,2, V. Kataev3, Yu. Pashkevich4, and G. Güntherodt1 — 12. Phys. Inst., RWTH Aachen — 2IMNF, TU Braunschweig — 32. Phys. Inst., Univ. zu Köln — 4Donetsk Phystech NASU, Donetsk, Ukraine
Cu2−yZnyV2O7 belongs to the multi-redox complex oxides nCuO·V2O5 with n=2. The 5-fold oxygen coordinated Cu2+ is the only magnetic ion. CuO5 polyhedra share edges and form chains. To study the interplay between the symmetry of exchange topology and magnetism in this system we investigated Zn-substituted samples using X-ray diffraction, magnetization and ESR. The undoped compound (y=0) crystallizes in the orthorhombic α-phase, space group Fdd2. It shows a Curie-Weiss paramagnetism at high temperatures and orders antiferromagnetically at TN=33.5 K. Below TN weak spontaneous magnetization and ferromagnetic resonance are observed indicative of the spin canting due to the Dzyaloshinsky-Moriya exchange. Surprisingly, a moderate Zn doping results in a qualitatively different magnetic behavior. Although the decrease of TN due to the spin dilution is small, weak ferromagnetism is not observed in the ordered state for y≥0.14. In the paramagnetic state susceptibility exhibits a broad maximum typical for the one-dimensional Heisenberg S=1/2 systems, albeit ESR data suggest an appreciable anisotropy of magnetic interaction. We find that the drastic change of magnetic properties is accompanied by a structural phase transition to the monoclinic β-phase, space group C2/c. We acknowledge support by DFG SPP1073.