The level-shifting-induced negative magnetoresistance
in the nearest-neighbor hopping conduction

X. R. Wang ¹, S. C. Ma ¹ and X. C. Xie ²

¹ Department of Physics, The Hong Kong University of Science and Technology
Clear Water Bay, Hong Kong
² Department of Physics, Oklahoma State University - Stillwater, OK 74078, USA

(received 21 July 1998; accepted in final form 26 November 1998)

PACS. 72.80Tm - Composite materials.
PACS. 75.70Pa - Giant magnetoresistance.
PACS. 81.05Rm - Porous materials; granular materials.

Abstract:

We propose a new mechanism of negative magnetoresistance in non-magnetic granular materials in which electron transport is dominated by hopping between two nearest-neighbor clusters. We study the dependence of magnetoresistance on temperature and separation between neighboring clusters. At a small separation we find a negative magnetoresistance at low temperatures and it changes over to a positive value as temperature increases. For a fixed temperature, magnetoresistance changes from negative to positive when the cluster separation increases. The change of magnetoresistance can be more than 80 % at low temperatures.

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