Abstract
We present results of an experimental study of magnetoresistance (MR) in insulating NbSi amorphous alloys sample showing Variable Range Hopping (VRH) conductivity. The MR is found to be negative in a wide range of low temperature (4.2-20 K) and in the range of moderate magnetic fields (0-4 T). We made tentative analysis using three theoretical models which are the model of quantum interference, the model of Zeeman effect and the model of localized magnetic moments
Highlights
For few decades, the negative magnetoresistance (NMR) of doped semiconductors has been the subject of investigations, as much in the metallic regime [1,2,3] as in insulating systems [4,5]
The most recent theories are based on the quantum corrections, which are enhanced in the neighbourhood of the Metal-Insulator Transition (MIT)
Theories on quantum interference effects in the variable range hopping (VRH) regime [8] is in a good agreement with experiment for very low magnetic fields
Summary
The negative magnetoresistance (NMR) of doped semiconductors has been the subject of investigations, as much in the metallic regime [1,2,3] as in insulating systems [4,5]. Theories on quantum interference effects in the variable range hopping (VRH) regime [8] is in a good agreement with experiment for very low magnetic fields. Toyozawa [9] proposed that the negative magnetoresistance is a consequence of alignment of local magnetic moments by the applied magnetic field. In order to consider only the negative part of the MR (Figure 2), the present paper is devoted to a tentative analysis of the negative MR of insulating a-NbSi sample in the temperature range 4.2 - 20 K and in magnetic fields up to 2.5 T using several theoretical models. The Variable Range Hopping (VRH) conduction has been observed in this sample, and all the conductivity data, for different magnetic fields, follows a universal VRH law given by:. In this work we have attempted to decide for one of the two VRH regimes by studying the behaviour of negative magnetoresistance
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