Dresden 2011 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 1: Multiferroics I (Joint Session of MA, DF, DS, KR, TT)
KR 1.5: Vortrag
Montag, 14. März 2011, 15:45–16:00, HSZ 04
Dilatometric studies of the multiferroic FeTe2O5Br — •Christian Balz1, Mariano de Souza1, Matej Pregelj2, Helmuth Berger3, Denis Arčon2, and Michael Lang1 — 1Physikalisches Institut, Goethe-Universität, D-60438 Frankfurt(M), SFB/TR49, Germany — 2Institute "Jozef Stefan", Jamova 39, 1000 Ljubljana, Slovenia — 3Institute of Physics of Complex Matter, EPFL, 1015 Lausanne, Switzerland
We report on high-resolution directional dependent thermal expansion measurements of the novel multiferroic system FeTe2O5Br [1]. Our results reveal two distinct phase transition anomalies centered at TN1=11.0 K and TN2=10.6 K, which coincide with the transitions observed in other quantities [2]. A rounded minimum in αc shows that short-range magnetic correlations within the crystal layers start to develop already above TN. At TN1, the system undergoes a magnetic phase transition into the high-T incommensurate (HT-ICM) phase. Interestingly, at TN2, a second phase transition into the low-T incommensurately modulated (LT-ICM) phase is observed, which is accompanied by a spontaneous electric polarization. When magnetic field is applied, the transition temperatures shift depending on the field orientation. In the case of B||b>4.5 T, the HT-ICM phase merges into the LT-ICM phase. Despite the pronounced lattice effects observed at TN2 at 6 T, the electric polarization is destroyed. The rich low-T magnetic phase diagram of FeTe2O5Br will be discussed in details [2].
M. Pregelj et al., Phys. Rev. Lett. 103, 147202 (2009).
M. Pregelj et al., Phys. Rev. B 82, 144438 (2010).