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Magnetotransport in Metals and Alloys

Magnetism and Magnetic Measurement

  1. Jack Bass

Published Online: 18 MAY 2012

DOI: 10.1002/0471266965.com047.pub2

Characterization of Materials

Characterization of Materials

How to Cite

Bass, J. 2012. Magnetotransport in Metals and Alloys. Characterization of Materials. 1–13.

Author Information

  1. Michigan State University, East Lansing, MI, USA

Publication History

  1. Published Online: 18 MAY 2012

Abstract

Electronic transport properties are fundamental to the classification of materials. The behaviors of the electrical resistivity ρ, the thermal conductivity κ, and the thermopower S are used to define whether a material is a metal, a semiconductor, or an insulator. Studies of how ρ, κ, and S vary with impurity content (alloying), magnetic field B, sample size, deformation, and so on, provide insight into the nature of current carriers and how they are scattered. Studies of magnetoresistance, the variation of ρ with B, can yield additional information about electronic structure, the current carriers, and their scattering. In systems involving magnetic metals, ρ(B) has technical applications to magnetic sensing and memory. The Hall effect and the thermopower S can often be used to infer the sign of the charge of the majority current carriers, and the thermal conductivity κ, while closely related to ρ, can manifest differences that contain significant information. The Hall effect in semiconductors also finds use in sensors, but in metals it is smaller and usually of more interest for the physical insight it can provide into both nonmagnetic and magnetic metals. Changes with magnetic field in the thermal conductivity and thermoelectric coefficients of metals are usually small and difficult to measure. They have provided useful information about physical phenomena such as many-body contributions to thermoelectricity and giant magnetoresistance in granular alloys and magnetic multilayers but are much less studied than the resistivity and Hall effect. Transport and magnetotransport measurements of metals and alloys are made over a wide range of temperatures extending from the lowest achievable temperature to the liquid state.

This article focuses on four measured quantities in solid metals and alloys in the presence of a temporally constant and spatially uniform magnetic field B—the electrical resistance R, the Hall resistance RH, the thermal conductance K, and the thermopower S. The basic theory underlying these quantities applies also to liquid metals and alloys. The discussion begins with definitions and general information, including how to relate the measured quantities to the fundamental properties ρ, the Hall coefficient R0, κ, and S. These are followed by a brief description of the behaviors of ρ, κ, and S in zero magnetic field. Many more quantities than these four can be defined and measured, some of which have provided important information about metals. A few are briefly discussed.

Keywords:

  • electronic transport;
  • magnetotransport;
  • Hall resistance;
  • transport equations;
  • thermopower;
  • magnetoresistance;
  • Peltier heat