Adiabatic magnetization of antiferromagnets

Abstract

Spin-wave theory was used to determine the magnetic field dependence of the thermodynamic properties of cubic or uniaxial antiferromagnets at temperatures well below the Néel point. These properties were found to be exponentially increasing functions of applied field for values of H0 less than the critical spin-flopping field. This field dependence suggests that if spin wave effects are dominant an antiferromagnet can be cooled by adiabatic magnetization in contradistinction to the paramagnetic case of cooling by demagnetization. (The phenomenon of antiferromagnetic cooling by isentropic magnetization was recognized many years ago.) Both lattice and nuclear effects can alter the situation in a real material and were included in this investigation. The dependence of adiabatic magnetization cooling on the physical quantities characterizing the antiferromagnet is discussed and theoretical temperature changes for several uniaxial antiferromagnets are given. © 1963 The American Institute of Physics.