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DPG

Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Poster:ThinFilms(1-33),Transp.(34-49),ExchBias(50-56),
Spindynamics(57-70),Micro-nanostr.Mat.(71-82),
Particles/Clust.(83-88), Mag.Imag./Surface(89-96),
Spinelectronics(97-109), Theory/Micromag.(110-116),
Spinstruct/Phasetr.(117-128),Magn.Mat.(129-139),
Aniso.+Measuring(140-145), MolMag.(146-152),
MSMA(153-156)

MA 15.118: Poster

Dienstag, 27. März 2007, 15:00–19:00, Poster A

Thermal Expansion and Thermal Transport in NdMnO3 and TbMnO3 — •Kai Berggold1, Thomas Lorenz1, Jörg Baier1, John Mydosh1, Dennis Meier2, Joachim Hemberger3, and Dimitri Argyriou41II. Physikalisches Institut, University of Cologne, Germany — 2Helmholtz - Inst. f. Strahlen und Kernphysik, University of Bonn, Germany — 3Inst. f. Physik, University of Augsburg, Germany — 4Hahn-Meitner-Institut, 14109 Berlin, Germany

We present measurements of the thermal expansion α and the thermal conductivity κ of NdMnO3 and TbMnO3. NdMnO3 is an A type antiferromagnet with TN=88 K, whereas TbMnO3 is known for its multiferroic properties, leading to complex magnetic and electric ordering phenomena at low temperatures. In NdMnO3, the Néel transition causes large anomalies in α as well as in κ. At low temperatures the crystal-field splitting of the Nd3+ ground state causes a Schottky-type contribution to the thermal expansion. The thermal conductivity at low temperatures is strongly suppressed by this splitting, as a consequence of resonant phonon-scattering processes. In TbMnO3, we show that the main factor determining κ is also given by resonant scattering between different crystal-field split states of the 4f multiplet of the Tb3+ ions. In contrast to NdMnO3, the suppression acts in a much wider temperature range. The various transitions at low temperatures observed by anomalies of the thermal expansion have no significant influence on the thermal conductivity.

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