Magnetotransport in Metals and Alloys

Abstract

AbstractElectronic transport properties are fundamental to the classification of materials. The behaviors of the electrical resistivity ρ, the thermal conductivity κ, and the thermopowerSare used to define whether a material is a metal, a semi‐conductor, or an insulator. Studies of how ρ, κ, andSvary with impurity content (alloying), magnetic fieldB, sample size, deformation, etc., provide insight into the nature of current carriers and how they are scattered. Studies of magnetoresistance, the variation of ρ withB, can yield additional information about electronic structure, the current carriers, and their scattering. In systems involving magnetic metals,has technical applications to magnetic sensing and memory. The Hall effect and the thermopowerScan 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 fieldB—the electrical resistanceR, the Hall resistance, the thermal conductanceK, and the thermopowerS. 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, κ, andS. These are followed by a brief description of the behaviors of ρ, κ, andSin 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.