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.

DOI: 10.12693/APhysPolA.109.611 PACS numbers: 74.72.-h, 74.25.Fy, 73.43.Qt