Quantum mechanics

Magnetic field

Engineering

Magnetization

Exploit

Materials science

Magnetic hysteresis

Cooling capacity

Ferromagnetism

Computer security

Computer science

Scaling

Heat exchanger

Mechanical engineering

Thermodynamics

Physics

Hysteresis

Mathematics

Thermal

Magnetic refrigeration

Condensed matter physics

Geometry

Refrigeration

Magnet

Refrigerant

Nature Materials

The giant magnetocaloric effect, in which large thermal changes are induced in a material on the application of a magnetic field, can be used for refrigeration applications, such as the cooling of systems from a small to a relatively large scale. However, commercial uptake is limited. We propose an approach to magnetic cooling that rejects the conventional idea that the hysteresis inherent in magnetostructural phase-change materials must be minimized to maximize the reversible magnetocaloric effect. Instead, we introduce a second stimulus, uniaxial stress, so that we can exploit the hysteresis. This allows us to lock-in the ferromagnetic phase as the magnetizing field is removed, which drastically removes the volume of the magnetic field source and so reduces the amount of expensive Nd–Fe–B permanent magnets needed for a magnetic refrigerator. In addition, the mass ratio between the magnetocaloric material and the permanent magnet can be increased, which allows scaling of the cooling power of a device simply by increasing the refrigerant body. The technical feasibility of this hysteresis-positive approach is demonstrated using Ni–Mn–In Heusler alloys. Our study could lead to an enhanced usage of the giant magnetocaloric effect in commercial applications. Magnetocaloric effects can be used for refrigeration, but application uptake is limited due to large amounts of magnetic material used. Here, a cooling cycle is shown that uses thermal hysteresis, significantly reducing magnetic material quantity.

A multicaloric cooling cycle that exploits thermal hysteresis