Magnetocaloric

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... 

Tables 9.1 and 9.2 show how non-zero-dimensional compounds can have the largest MCEs. Even amongst this non-exhaustive selection, these compounds have larger Gd(III) percentages and densities. It is possible, of course, to synthesize polymeric compounds with inferior performance. However, these represent a new tool in the arsenal of magnetocaloric research, which, as we will see below, has been extremely successful, including in 3d-4f materials.

There is nothing intrinsically superior about non-zero-dimensional materials compared to lanthanide cages as magnetocaloric materials, but, thus far, synthetic chemists have been unable to realize as many of the required properties in cages simultaneously, as they have done with some chains and lattices. The key advantage is cramming in as many metals as possible into a structure with as few ligands as possible. 

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

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