Magnetovolume effects in strongly correlated plutonium phases

Thermodynamic spin fluctuations in strongly correlated plutonium (Pu) phases with exchange and spin–orbit interactions are considered. In $\alpha$- and $\delta$-Pu phases, the spin fluctuations lead to a negative magnetovolume effect that is determined by the parameter of intermode coupling and depends on features of the electron structure. It is shown that the negative volumetric thermal expansion coefficient of $\delta$-Pu is related to an anomalously strong interaction of spin fluctuation modes.