Abstract
We suggest a thermodynamically and mathematically consistent analysis of magnetocaloric effect for a plate immersed in a uniform static magnetic field. We ignore deformability of the plate, but make no assumption regarding the amplitude of the magnetic field - it can be arbitrarily large. Traditional presentations of magnetocaloric effect are rather simple and straightforward - they are based on the algebraic manipulations with thermodynamic identities, and no analysis of boundary value problems is required. But they suffer one conceptual drawback - they are dealing with the magnetic field inside the specimen. However, the interior field is, a priori, unknown and depends on the geometry of the specimen. In fact, the meaningful analysis should be based on usage of the experimentally controllable exterior field. The relevant analysis therefore, should be based on the consideration of the boundary value problem for the equations of magnetostatics. We establish the relevant relationships of the magnetocaloric effect for the sample in the shape of a plate.
Highlights
Per the classical definition, “The magnetocaloric effect (MCE, from magnet and calorie) is a magneto-thermodynamic phenomenon in which a temperature change of a suitable material is caused by exposing the material to a changing magnetic field...”
The phenomenon was widely used in low temperature physics instead of traditional adiabatic cooling caused by mechanically induced expansion
In the low temperature physics the magnetocaloric effect is known as adiabatic demagnetization
Summary
Per the classical definition (https://en.wikipedia.org/_ wiki/Magnetic_refrigeration), “The magnetocaloric effect (MCE, from magnet and calorie) is a magneto-thermodynamic phenomenon in which a temperature change of a suitable material is caused by exposing the material to a changing magnetic field...” The phenomenon was widely used in low temperature physics instead of traditional adiabatic cooling caused by mechanically induced expansion. In phenomenological thermodynamics of magnetism of nondeformable substances we introduce free energy density per unit volume Ψ which is the function of the magnetization M i per unit volume and the absolute temperature T - Ψ = Ψ(M ,T ) ; here and in the following we omit indices in the arguments. The identity is applicable to the bodies of arbitrary geometry - no geometry whatsoever appears in this formula The cost for this universality is rather high, . We need the relationship between the equilibrium temperature and the field This formula is not as universal as the Equation (5), it depends upon the geometry of the system and its determination is based on solving boundary value problems for different geometries of the magnetizable bodies. Equation (6) implies the continuity of the tangential components of the magnetic field; that fact can be presented in the form k.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
