Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 44: Poster Session Correlated Electrons

TT 44.34: Poster

Thursday, March 17, 2011, 10:00–13:00, P1

Phase diagram of NaFe(WO₄)₂ — •Yvonne Sanders¹, Stephanie Orbe¹, Oliver Heyer¹, Sven Jodlauk², Sebastian Albiez², Petra Becker², Ladislav Bohatý², and Thomas Lorenz¹ — ¹II. Physikalisches Institut, University of Cologne, Germany — ²Institut für Kristallographie, University of Cologne, Germany

Multiferroic materials show simultaneous ferroelectric and magnetic order, which are strongly coupled to each other. A well-known model system is MnWO₄ with only one kind of magnetic ions and three magnetically ordered phases below ∼13 K. Here, the multiferroic behavior of one of these phases arises from an incommensurate spin spiral structure. Much less is known about the double tungstate NaFe(WO₄)₂, which has a structure closely related to MnWO₄. While in MnWO₄ sheets || (100) of MnO₆ zig-zag chains alternate with similar sheets of WO₆, in NaFe(WO₄)₂ an alternating sheet sequence FeO₆-WO₆-NaO₆-WO₆ - is found. Consequently, the a lattice parameter is doubled and the magnetic subsystem is diluted. The ordering temperature in NaFe(WO₄)₂ is reduced to T_N≈ 4 K. The magnetic structure in zero magnetic field is reported to be collinear antiferromagnetic, but the H-T phase diagram has not been published so far. Here, we present a detailed study of this phase diagram obtained by high-resolution thermal expansion and magnetostriction measurements. We find pronounced hysteresis effects, which resemble those observed in other multiferroic materials.

Supported by the DFG through SFB 608.