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MA: Magnetismus

MA 5: Spin-Structures and Magnetic Phase Transitions I

MA 5.3: Vortrag

Montag, 27. März 2006, 10:45–11:00, HSZ 403

Phase diagram of the multiferroic GdMnO₃ studied by thermal expansion and magnetostriction — •J. Baier¹, D. Meier¹, V. Ivanov², A. Mukhin², A. Balbashov³, J. Hemberger^1,4, and T. Lorenz¹ — ¹II. Phys. Institut, University of Cologne, Germany — ²General Physics Institute, Russian Academy of Sciences, Moscow, Russia — ³Moscow Power Engineering Institute, Moscow, Russia — ⁴Institut f. Physik, University of Augsburg, Germany

Recently, the discovery of very large magnetoelectric effects in rare earth manganites RMnO₃ has reopened the field of the so called multiferroic materials [1]. We present a study of the phase diagram of multiferroic GdMnO₃ by thermal expansion α(T,H) and magnetostriction є(H,T). GdMnO₃ shows an incommensurate antiferromagnetic order (ICAFM) below T_N≃ 43 K. Further decrease of temperature leads to a canted A-type antiferromagnetic ordering (cAFM) below T_lock≃ 23 K. Above a critical magnetic field along the b direction ferroelectric order (FE, P||a) emerges below T_c≃ 10 K [1]. In zero magnetic field, we already observe an anomalous and anisotropic thermal expansion, but upon applying a magnetic field, very strong, new anomalies arise at the cAFM and ferroelectric phase boundary. Both phase transitions are of first-order type and display a very strong hysteresis. Furthermore we observe a down-bending of the ICAFM-to-cAFM boundary (T_lock) at low magnetic fields.

[1] T. Kimura et al., Nature 426, 55 (2003), T. Kimura et al., PRB 71, 224425 (2005)

Supported by the DFG through SFB 608