Change of Thermal Energy with Adiabatic Change of Magnetization in Iron, Nickel and Carbon Steel

Abstract

Previous methods for measuring the change in thermal energy which occurs when the magnetization of a ferromagnetic material is altered adiabatically have been so improved as to permit a precise study of this phenomenon in magnetically soft materials. The materials here dealt with are carbon steel, and annealed and unannealed Armco iron and nickel. The change in thermal energy of each of these substances is traced through a complete half-cycle of magnetization which starts with the maximum value of the intensity of magnetization. The external work done by the specimen at each stage of the process is likewise evaluated. The decrease in thermal energy on demagnetization is less than the external work done by the specimen in iron and steel, while in unannealed nickel it is greater. In annealed nickel the decrease in thermal energy is greater than the external work when the magnetization process is continuous and less when it is discontinuous.