Van Vleck paramagnetism

Not much attention had been paid to this (21) until Dorf man 22) showed that Eq. (4) was often roughly true and suggested that the difference between the observed and that from Eq. (4) was simply due to the van Vleck paramagnetism. 

Another additive term in the magnetic susceptibility arises from the temperature-independent core diamagnetism of all the ions in a solid. For YBa2Cu307 the core diamagnetism is approximately -2 x 10 7 based on a calculation using Pascal s constants (9). This small negative contribution serves to reduce the total susceptibility. A third possible contribution arises from Van Vleck paramagnetism (10) caused by excited states in the atoms of the... 

SmFe4Pn is a metal that shows Van Vleck paramagnetism (Jeitschko et al., 2000). 

The heat capacity behavior of PrNi2 confirms that it becomes a Van Vleck paramagnet at low temperatures (65). It exhibits no X-type thermal anomaly expected if there is magnetic ordering only a Schottky-type heat capacity excess is observed. This is a consequence of the thermal population of the higher crystal field states. 

Wilson and Laity claim that the incremental bond system used in the construction of the model 19> will include the Van Vleck paramagnetism of the localised 2pn electrons. Accordingly, they attribute the observed exaltations to the presence of ring currents (London diamagnetism). 

The results show that the magnetic susceptibility of these carbides agrees well with a Curie-Weiss law of the form X = Xq + (C/T — 0 ) above the temperature T. The only exception is samarium hypocarbide, for which a deviation from this law has been observed. This type of deviation also occurs in SmC2 and has been attributed to Van Vleck paramagnetism. 

Here ps is the Bohr magneton, p is the effective number of Bohr magnetons, and ks is Boltzman s constant. Thus a plot of 1 // versus temperature is a straight line with an intercept at zero. Other contributions to the susceptibility of an isolated molecule include core diamagnetism and Van Vleck paramagnetism, both of which are small and temperature independent (231). 

The term Van Vleck paramagnetism is mainly used in atom physics, and the term induced orbital paramagnetism referring to molecules.Riess, J. (1970) J. Ann. Phys., 57, 301-321. 

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