Negative Magnetoresistance in the Variable-Range-Hopping Transport of Strongly Underdoped La2-xSrxCuO4

A. Malinowskia, M.Z. Cieplaka, M. Berkowski a and S. Guhab aInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland bDepartment of Physics and Astronomy, Rutgers University, Piscataway, NJ 08885, USA

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Received: 25 09 2005;

The in-plane transport of strongly underdoped La2-xSrxCuO4 films was examined in the magnetic fields up to 14 T and in temperatures down to 1.6 K. While at high temperatures the samples display metallic-like resistivity, the low-T transport is governed by variable-range-hopping mechanism. Careful analysis shows that the temperature dependence of pre-exponential factor in Mott's variable-range-hopping law may not be neglected and that the density of states at the Fermi level can be effectively expressed as g(E-EF)=N0 (E-EF)p, with a small exponent p of the order of 0.1. In the magnetic field parallel to CuO2 planes one of the variable-range-hopping parameter,ρ0, increases by about 20-25%, while the other one, T0, decreases by about 10-15%, resulting in the decrease in total resistivity. This effect may be related to the decrease of the tunneling barrier between different antiferromagnetic clusters in the presence of magnetic field.

PACS numbers: 74.72.-h, 74.25.Fy, 73.43.Qt