Magnetocaloric effect

MNMs are promising materials for low temperature refrigeration applications. Derivatives of Fei4 and ferromagnetically 

The above physical quantity, denoted by AS and expressed in J K , is called the field-induced isothermal magnetic entropy change or simply isothermal magnetic entropy change. 

From the magnetic entropy change it is easy to calculate the cooling capacity Q of the magnetic material, that is, the amount of heat that can be extracted from the cold end to the hot end of a refrigerator in one ideal thermodynamic cycle by integrating the following differential equation  

Secondly, if the magnetic material is magnetized adiabatically, that is, without exchange of heat with the surroundings (i.e., isolated system), the total entropy of the system remains constant while the temperature of the materials varies according to the following equation  

This variation, called the adiabatic temperature change calculation of the isothermal magnetic entropy change, is based on the following Maxwell relation  

The calculation of both the specific and entropy density changes is still based on the Maxwell relationships introducing the mass density of the material fr. 

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Table 4.1 Characteristic values of selected gadolinium-based systems exhibiting magnetocaloric effects.

Tishin, A.M. and Spichkin, Y.I. (2003) The Magnetocaloric Effect and its Applications, Taylor Francis Group, London. 

A large nuclearity cluster, with lots of high-spin ions, is not necessarily the route to the largest magnetocaloric effect. There are deeper factors, such as exchange interactions, which we now explore. 

If we first consider the three scenarios at the same field, we can immediately see how the paramagnetic material shows the largest magnetocaloric effect, followed by a ferromagnetically coupled system, and then the antiferromagnetic case. 

Table 9.2 List of selected compounds with -ASM, their density and adjusted magnetocaloric effect.

Of the lanthanide (III) ions, gadolinium(III) is exceptional, being the only isotropic paramagnetic ion of this series. Anisotropy, D, in 3d systems has been shown to hinder a large magnetocaloric effect at low temperatures as demonstrated by... 

Important Concepts for a Large Magnetocaloric Effect 298 Spin 298 Examples 299... 

III.1 The magnetocaloric effect Scientific American, May 1998, p. 44) relies on the ability of a ferromagnetic material to heat up in the presence of a magnetic field and then cool down once the field is removed. When a ferromagnet is... 

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