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Negative Magnetoresistance in the Variable-Range-Hopping Transport of Strongly Underdoped La_{2-x}Sr_xCuO_4

100%

Malinowski A., Cieplak M., Berkowski M., Guha S.

Acta Physica Polonica A

2006

vol. 109

issue 4-5

611-615

The in-plane transport of strongly underdoped La_{2-x}Sr_xCuO_4 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-E_F)=N_0 (E-E_F)^p, with a small exponent p of the order of 0.1. In the magnetic field parallel to CuO_2 planes one of the variable-range-hopping parameter,ρ_0, increases by about 20-25%, while the other one, T_0, 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.

Microstructure of the Pulsed Laser Deposited LaSrCuO Films

76%

Cieplak M., Abal'oshev A., Zaytseva I., Berkowski M., Guha S., Wu Q.

Acta Physica Polonica A

2006

vol. 109

issue 4-5

573-576

The X-ray diffraction and atomic force microscopy are used to examine the microstructure of La_{1.85}Sr_{0.15}CuO_4 films grown by pulsed laser deposition on LaSrAlO_4 substrates. The films grow with different degrees of built-in strain, ranging from a large compressive to a large tensile in-plain strain. The tensile strain cannot be attributed to a substrate-related strain. The possible origins of the tensile strain are discussed.

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2 Acta Physica Polonica A

2 2006

2 Berkowski M.

2 Cieplak M.

2 Guha S.

1 Abal'oshev A.

1 Malinowski A.

1 Wu Q.

1 Zaytseva I.

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Negative Magnetoresistance in the Variable-Range-Hopping Transport of Strongly Underdoped La_{2-x}Sr_xCuO_4

Microstructure of the Pulsed Laser Deposited LaSrCuO Films