•  Magnetocaloric materials and magnetic refrigeration

magnetocaloric refrigeration


Magnetic refrigeration is a cooling technology based on the magnetocaloric effect, i.e. solid magnetic materials heat up or cool down when an external magnetic field is applied or removed. The basic operating principle of magnetic refrigeration is similar to that of vapor-compression refrigeration. However, the efficiency of magnetic refrigeration can reach up to 60 %, compared with only 40 % in vapor-compression-refrigeration. Besides, solid magnetic refrigerants are employed instead of gases. Thus, there is no gas compressor. As a result, magnetic refrigeration generates less noise and vibrations, and does not use ozone-depleting and hazardous chemicals, or greenhouse gases, e.g. chlorofluorocarbons (CFCs), ammonia (NH3), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Magnetic refrigeration is therefore considered to be a revolutionary, energy-efficient and environmentally friendly cooling technology.

 

Magnetocaloric materials play an important role in magnetic refrigeration. The development of advanced magnetocaloric materials is a prerequisite for commercializing magnetic refrigeration technology. Although considerable success has been achieved in developing magnetic refrigerants, the search for novel working materials or optimizing known magnetocaloric materials is still an important task in order to find suitable materials for application.



  • Diluted magnetic semiconductors

 


Magnetic semiconductors are semiconductor materials that exhibit both ferromagnetism and useful semiconductor properties. These materials could provide a new type of control of conduction. Unlike traditional electronics which are based on control of charge carriers (n- or p-type), practical magnetic semiconductors would also allow control of quantum spin state (up or down). This would theoretically provide near-total spin polarization (as opposed to iron and other metals, which provide only ~50% polarization), which is an important property for spintronics applications, e.g. spin transistors.

 

Diluted magnetic semiconductors have recently been a major focus of magnetic semiconductor research. These are based on traditional semiconductors, but are doped with transition metals (Mn, Fe, Co, Ni) or even with non-magnetic elements (Cu, C).