Berlin 2005 – wissenschaftliches Programm

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MA: Magnetismus

MA 5: Spinstrukturen und magnetische Phasenüberg
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MA 5.8: Vortrag

Freitag, 4. März 2005, 12:15–12:30, TU EMH225

Substitution of Manganese in electron-doped manganites — •Uwe Amann^1,2, Clemens Ritter², Dietmar Hohlwein^1,3, and Jörg Ihringer¹ — ¹Universität Tübingen, Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen, Germany — ²Institut Laue-Langevin, 6, Rue Jules Horowitz, B.P. 156, 38042 Grenoble, France — ³Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin, Germany

As part of a systematic investigation[1,2,3] of substitution effects of Manganese by other trivalent atoms, we investigated the temperature-dependant evolution of the magnetic moments in the CMR-compound Y_0.1Ca_0.9Ga_1−xMn_xO₃ for x = 0.0, 0.02, 0.04.

For temperatures above the Neel temperature the samples display monophase Pnma structure. With the onset of magnetic ordering, the system splits into at least two phases, an antiferromagnetic G-type ordered matrix into which ferromagnetic regions (FM) are embedded and a second, monoclinic antiferromagnetic (M-AFM) phase in nuclear space group P2₁/m.

Substitution with different ions acts differently on the magnetic structure: Iron inhibits the formation of FM and M-AFM phases, but doesn’t disturb the magnetic exchange paths, so there is no change in phase transition temperature. Gallium on the other hand, without magnetic moment, disturbs the exchange paths, shifting the phase transition to lower temperatures.

[1]Th. Lottermoser, Nature 430 (2004), 541-544.

[2]U. Amann et al., Z. Krist, Suppl. 18 (2000), 79