Magnetothermal Effects

changes in the thermal state of bodies upon changes in their magnetic state (magnetization or demagnetization). A distinction is made between the magnetic effects that occur upon an adiabatic change in magnetic state (the magnetocaloric effect, in which the temperature of the body changes) and isothermic magnetic effects (in which heat is released or absorbed).

In principle, magnetothermal effects can be observed in any substance, since they have a common thermodynamic cause— the change in the body’s internal energy upon changes in its magnetic state. Magnetothermal effects are especially significant in ferromagnets, antiferromagnets, and ferrimagnets; the character of magnetothermal effects in these substances depends on what magnetization processes take place within them: (1) displacement of the domain boundaries, (2) rotation of the magnetic moment of the domains, (3) the paraprocess, (4) processes of destruction or induction of noncollinear magnetic structure (in antiferromagnets and ferrimagnets). The thermal effects that accompany the last two processes are especially great. The anomalies of specific heat near the Curie and Neel temperatures and other points of magnetic phase transitions (for example, near the point at which the noncollinear magnetic structure of a ferrimagnet changes), which are observed in ferromagnets, antiferromagnets, and ferrimagnets, are thermodynamically closely related to the magnetothermal effects that occur upon magnetization. In some paramagnets, magnetothermal effects are used to produce extremely low temperatures.