Ferromagnetic antiferromagnetism

There are several types of magnetic behaviour that affect the specific heat of a material paramagnetism, ferromagnetism, antiferromagnetism and ferrimagnetism. Diamagnetism, being independent of temperature, causes no specific heat contribution and is not considered. 

The symbols F, AF, mean that the compound under consideration becomes ferromagnetic (antiferromagnetic) at low temperature, the Curie (Neel) temperature being labeled T (Tn). 

ORDER-DISORDER THEORY AND APPLICATIONS. Phase transitions in binary liquid solutions, gas condensations, order-disorder transitions in alloys, ferromagnetism, antiferromagnetism, ferroelectncity, anti-ferroelectricity, localized absorptions, helix-coil transitions in biological polymers and the one-dimensional growth of linear colloidal aggregates are all examples of transitions between an ordered and a disordered state. 

FIGURE 3.3 Temperature dependence of yT (a), y (b), and 1 /y (c) for a ferromagnetically, antiferromagnetically, and uncoupled spin-1/2 dimer as calculated by the Bleaney-Bowers equation (Equation 3.12). 

Fermi energy relative to the bottom of the CB). The Fermi level wave lengths are in general incommensurable with the crystal s interatomic or interplanar distances as a result, the magnetic ground states of the rare-earth intermetallics and pure metals have complicated spatial distributions, ferromagnetic, antiferromagnetic, helical, etc. 

At low temperatures, there are at least two ways in which the f electrons, and their magnetic moments, behave either they order spontaneously in ferromagnetic, antiferromagnetic or complicated magnetic structures, or the f electrons can form a heavy fermion state, strongly correlated with the conduction electrons. 

As it follows from (12), ground-state averages of orbital pseudo spin operators determine the numeric values of Q (i) and, thereby, the respective symmetry-adapted distortion of every elementary cell of the crystal. Instead of ferromagnetic , antiferromagnetic , etc., the appropriate name to use is ferrodistortive , antiferrodistortive , etc. 

With the exception of lattice defects and semiconducting materials, these will not be discussed further here. In Section 20.8, we introduced some concepts of magnetism including ferromagnetism, antiferromagnetism and ferrimag-netism although these properties are important in materials chemistry, it is beyond the scope of this book to take this topic further. 

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