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Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.132: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Thermal expansion of multiferroic manganites in magnetic fields — •D. Meier1, J. Baier1, O. Heyer1, J. Hemberger2, D. Argyriou3, N. Aliouane3, A. Freimuth1, and T. Lorenz11II. Physikalisches Institut, University of Cologne, 50937Cologne, Germany — 2Institut für Physik, University of Augsburg, 86159 Augsburg,Germany — 3Hahn-Meitner-Institut, 14109 Berlin, Germany

Strong coupling between magnetic and ferroelectric ordering in some perovskite rare-earth manganites RMnO3 (R = Gd, Tb) gave rise to intense investigation on these multiferroics. We present high-resolution measurements of thermal expansion and magnetostriction on RMnO3 (R=Nd, Gd, Tb). NdMnO3 is a non-multiferroic A-type antiferromagnet (TN=88K) serving as a reference compound. GdMnO3 shows antiferromagnetic order for T<TN=43K. Application of a magnetic field H||b induces an electric polarization P below T ≈ 10K. In contrast, TbMnO3 shows intrinsic ferroelectricity for T<Tlock=28K already in zero magnetic field. Depending on strength and direction of the magnetic field, P can be suppressed or changes its direction. Our mesurements reveal a huge magnetoelastic coupling, a strong hysteretic behavior and an anisotropic thermal expansion of these compounds. The investigation on the phase boundaries as a function of the magnetic field identifies a new phase transition in TbMnO3, a bending down of the Tlock-phase boundary in GdMnO3 for low magnatic fields and a shift of the ferroelectric transition down to lower temperatures in high fields.

This work was supported by the DFG through SFB 608.

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