Magnetocaloric Effect

Also found in: Acronyms.

Magnetocaloric effect

The reversible change of temperature accompanying the change of magnetization of a ferromagnetic or paramagnetic material. This change in temperature may be of the order of 1°C (2°F), and is not to be confused with the much smaller hysteresis heating effect, which is irreversible. See Thermal hysteresis

Magnetocaloric Effect


a change in the temperature of a magnetic substance upon an adiabatic change in the intensity H of the magnetic field in which the substance is located.

Energy of magnetization δ = JdH (where J is the magnetization) is achieved as the field changes by dH. According to the first law of thermodynamics, δA = δQ — dU, where δQ is the amount of heat imparted to a magnetic substance (equal to zero under adiabatic conditions) and dU is the change in the internal energy of the substance. Thus, when δQ = 0, work is accomplished only as a result of change in the internal energy (δA = —dU), which leads to a change in the temperature of the magnetic substance if its internal energy is dependent on temperature T. In paramagnetic and ferromagnetic substances, the magnetization J increases with H, that is, there is an increase in the number of atomic magnetic moments (spin or orbital) parallel to H. As a result, there is a reduction in the energy of paramagnets and ferromagnets with respect to the field and in their internal energy of exchange reaction. On the other hand, the internal energy of paramagnets and ferromagnets increases with T. Therefore, according to the Le Chatelier-Brown principle, heating of paramagnets and ferromagnets should take place on magnetization. For ferromagnets, this effect is at a maximum near the Curie point; for paramagnets, the magnetocaloric effect in-creases with a decrease in temperature. Upon an adiabatic reduction of the field, there is partial or total destruction (the latter when the field is shut off) of the ordered orientation of the moments at the expense of the internal energy. This leads to the cooling of the magnetic substance.


Vonsovskii, S. V. Magnetizm. Moscow, 1971.


magnetocaloric effect

[mag¦nēd·ō·kə′lȯr·ik i‚fekt]
The reversible change of temperature accompanying the change of magnetization of a ferromagnetic material.
References in periodicals archive ?
In the 1990s, Pecharsky (1) discovered a magnetocaloric material that has a large magnetocaloric effect near room temperature.
A magnetocaloric material exhibits a strong magnetocaloric effect near the Curie temperature, when the phase changes from paramagnetic to ferromagnetic.
Second, the magnetocaloric effect is largest over a relatively narrow temperature range.
The magnetocaloric effect causes the material in the bed to increase in temperature when it is magnetized.
The magnetocaloric effect is "the thermal response of a magnetic material to the change of an external magnetic field, which manifests as a change in its temperature," explained Mohamed Balli, a researcher in the physics department at the Universite de Sherbrooke in Quebec, Canada.
The researchers originally set out to measure the standard magnetocaloric effect in the multiferroic compound HoMn[sub.
Concurrently, the development of magnetic materials with "tunable" Curie temperatures allowed layered magnetic regenerator beds to be fabricated that exhibit a large magnetocaloric effect over a large temperature range (Smaili and Chahine 1997).
The magnetocaloric effect causes the temperature of the material in the bed to increase.
Another way to tune the magnetocaloric effect is to construct magnetic nanocomposites, says Robert D.
Cooling systems based on the magnetocaloric effect have the potential of significantly reducing energy consumption.
These compounds are characterized by low-volume expansion and a particularly large magnetocaloric effect.
Shyll's group now reports making a new composite that shows a magnetocaloric effect three to four times larger than the effect exhibited by current materials.