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AM: Magnetismus
AM 2: Magnetische Phasenüberg
änge, Elektronentheorie
AM 2.8: Talk
Monday, March 26, 2001, 12:00–12:15, S 5.4
Magnetic Properties and Phase Diagram of La(1-x)Sr(x)MnO(3) (x >= 0.5) — •Thomas Kurz1, Hans-Albrecht Krug von Nidda1, Joachim Hemberger1, Alois Loidl1, Boris Kochelaev2, Alexander Mukhin3, Alexander Balbashov4, and Vladimir Ivanshin2 — 1Experimental Physics 5, EKM, Institute of Physics, University of Augsburg, Universitätsstrasse 1, 86159 Augsburg, Germany — 2Department of Physics, Kazan State University, Kazan, 42008, Russia — 3General Physics Institute of the Russian Academy of Sciences, 117942 Moscow, Russia — 4Moscow Power Engineering Institute, 105835 Moscow, Russia
We present susceptibility, resistivity, and electron spin resonance (ESR) investigations of highly doped La(1-x)Sr(x)MnO(3) with 0.5 <= x <= 1.0. It will be discussed how far DeGennes’ theory, which deals with the competition of double vs. super exchange in perovskites, is fulfilled in this system. Single crystals were synthesised from La(2)O(3), SrCO(3) and Mn(3)O(4) by the floating-zone method. Susceptibility measurements yield a phase diagram which shows antiferromagnetic order within 0.65 <= x <= 1.00 below temperatures of about 250K. For Sr-concentrations 0.5 <= x <= 0.65, we compare the possibilities of canting and phase seperation in the low-temperature phase. Resistivity measurements reveal a transition from metallic (x < 0.65) to insulating behavior. In ESR, we focus on the resonance linewidth in the paramagnetic state. Its temperature dependence can be explained taking into account both spin-spin-interactions and polaron hopping.