Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Spin structures and Magnetic Phase Transitions
MA 15.7: Vortrag
Dienstag, 1. April 2014, 11:00–11:15, HSZ 403
Spin relaxation in frustrated 2D antiferromagnets α-ACr2O4 (A = Ca, Sr) — •Martina Schädler, Mamoun Hemmida, Hans-Albrecht Krug von Nidda, and Alois Loidl — Experimental Physics V, EKM, University of Augsburg, 86135 Augsburg, Germany
Electron Spin Resonance (ESR) measurements were performed at X-band (9.4 GHz) and Q-band (34 GHz) frequency on polycrystalline samples of α-CaCr2O4 and α-SrCr2O4. In both compounds the magnetic Cr3+ ions form slightly distorted triangular layers, representing a frustrated 2D Heisenberg antiferromagnet with alternating exchange. The spin-spin relaxation behavior derived from the temperature dependence of the ESR-linewidth (Δ H) exhibits two different regimes. At temperatures T > 2TN a BKT-like scenario [1,2] suggests the existence of Z2 vortices as observed in the prototype triangular lattice Heisenberg antiferromagnet CuCrO2 [3]. For TN < T < 2TN fluctuations due to the onset of 3D antiferromagnetic order seem to dominate.
We thank for sample preparation: S. Toth and B. Lake, Helmholtz Zentrum Berlin, Germany (α-CaCr2O4), S. E. Dutton and R. J. Cava, Princeton University, USA (α-SrCr2O4).
References: [1] V. L. Berezinskii, J. Exp. Theor. Phys. 32, 493 (1971). [2] J. M. Kosterlitz and D. J. Thouless, J. Phys. C 6, 1181 (1973). [3] M. Hemmida, H.-A. Krug von Nidda, and A. Loidl, J. Phys. Soc. Jpn. 80, 053707 (2011).