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 La_0.7Ca_0.3MnO₃ step-edge junctions in pulsed magnetic fields up to 50 T — •K. Dörr¹, N. Kozlova¹, M. Ziese², M. Kozlov¹, K.-H. Müller¹, and L. Schultz¹ — ¹IFW 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 La_0.7Ca_0.3MnO₃ 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 La_0.7Sr_0.3MnO₃ films.

This work is supported by DFG, FOR 520.

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