The Magnetoresistance of Nonsuperconducting Bi2Sr2CuOy Crystals

The normal-state charge transport of high-Tc cuprates has been one of the focuses in understanding the high-Tc mechanism.We recently studied the temperature-dependent ab-plane resistivity of Bi2Sr2CuOy crystals,and found that many of the as-grown crystals exhibited metallic conduction at high temperature,but localized behavior at low temperature.The magnetoresistance measurement has been performed on the crystals showing strong-localization behavior.It is found that in the low temperature regime the samples show positive magnetoresistance at low field,but negative at high field.The magnetic field corresponding to the maximum positive magnetoresistance shifts to the direction of low field with the increase of the temperature.However,in the high temperature regime,only the negative magnetoresistance is observed no matter how the field is.With further increase of the temperature the magnetoresistance effect becomes less prominent.By comparison of the magnetoresistance in longitudinal direction with that in