thermomagnetic

Thermomagnetic refers to phenomena in which temperature and magnetic properties are interdependent, or where magnetic fields couple to thermal gradients. In magnetic materials, the degree of magnetic order and the spontaneous magnetization generally decreases with increasing temperature and changes abruptly near characteristic temperatures such as the Curie temperature for ferromagnets or the Néel temperature for antiferromagnets.

A central thermomagnetic phenomenon is the magnetocaloric effect, where changes in magnetic field alter the magnetic entropy of a material. Aligning magnetic moments with a field reduces magnetic entropy and, under isothermal conditions, leads to heating; removing the field allows adiabatic cooling. The effect is strongest near magnetic phase transitions and is the basis for magnetic refrigeration research, with materials such as gadolinium and several Mn-based alloys.

In transport phenomena, temperature gradients in the presence of a magnetic field can generate electric fields or transverse heat flow. The Nernst effect produces a transverse electric field from a longitudinal temperature gradient in a magnetic field, while the Ettingshausen effect links a heat current to a transverse electric field in a magnetic field. These effects are studied in metals and semiconductors, including ferromagnets, and have potential for sensors and energy conversion applications.

Applications and relevance of thermomagnetic phenomena include magnetocaloric cooling, thermomagnetic sensors, and exploratory devices that exploit the coupling between thermal and magnetic properties. The field intersects magnetism, solid-state physics, and materials science, with ongoing research into new materials and devices.