Extended Debye model for molecular magnets

Heat-capacity data on ${\text{Mn}}_{12}$ are fitted within the extended Debye model that takes into account a continuum of optical modes as well as three different speeds of sound.

Figure 1

Heat capacity of ${\text{Mn}}_{12}$. The standard Debye model fails everywhere except for very low temperatures, while the extended Debye model perfectly fits the data.

Figure 2

Heat capacity of ${\text{Mn}}_{12}$ in $C\left(T\right)/T$ vs $T^2$ representation used to eliminate the small parasite term $C\left(T\right)\propto T$.

Figure 3

(Color online) Heat capacity of ${\text{Mn}}_{12}$ in the presentation used as a crucial test for different models. Only the model with three different acoustic phonon modes really fits the data.

Figure 4

Phonon density of states for ${\text{Mn}}_{12}$ within the extended Debye model.