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Regensburg 2004 – scientific programme

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MA: Magnetismus

MA 22: Spinabh
ängiger Transport I

MA 22.2: Talk

Thursday, March 11, 2004, 12:30–12:45, H22

Magnetoresistance and resistance relaxation of La0.7Ca0.3MnO3 step-edge junctions in pulsed magnetic fields up to 50 T — •K. Dörr1, N. Kozlova1, M. Ziese2, M. Kozlov1, K.-H. Müller1, and L. Schultz11IFW Dresden, Postfach 270116, 01171 Dresden — 2Division of Superconductivity and Magnetism, University of Leipzig, Linnéstrasse 5, 04103 Leipzig

The magnetoresistance (MR) of step-edge junctions in La0.7Ca0.3MnO3 films [1] has been investigated in magnetic fields up to 47 T between 4.2 K and 125 K. Step-edge junctions show similar electrical properties as grain boundaries [1], including the low-field MR attributed to spin-polarized tunneling. A tendency towards saturation in high fields and a large hysteresis with pronounced remanent MR are characteristic results. Time-dependent resistance data R(t) recorded after field pulses of 7 T follow a logarithmic law for 30 ms < t < 50 s, with a maximum of the relaxation rate at 18 K. Both, MR and relaxation behavior strongly indicate a spin glass-like magnetic order at the junctions. Results will be compared with those obtained for polycrystalline La0.7Sr0.3MnO3 films.

This work is supported by DFG, FOR 520.

[1] M. Ziese et al., Appl. Phys. Lett. 74 (1999) 1481.

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