  A comparative study of the magnetocaloric effect (MCE) in metals within the
single-band Hubbard model on the face-centered cubic (fcc) lattice using both
mean-field (Stoner) approximation (MFA) and dynamical mean-field theory (DMFT)
is done. The MCE is investigated in the case of second order magnetic phase
transition from ferromagnet to paramagnet. To ensure presence of itinerant
ferromagnetism in the Hubbard model the special case of spectrum parameters
generating giant van Hove singularity at the bottom of the band is considered,
while the Fermi level $E_{\rm f}$ is in the vinicity of the band bottom. To
compare MCE within MFA and DMFT temperature dependence of magnetization, total
energy and finally entropy for a set of Coulomb interactions $U$ at zero and
finite values of magnetic field $h$ for both methods were performed. Also one
of the MCE potentials, isothermal entropy change, as a function of temperature
$\Delta S (T)$ for both MFA and DMFT is calculated. In the MFA, the expected
maximum value of $\Delta S (T)$ at the Curie temperature $T_C$ ($\Delta S_{\rm
max}$) quite significantly decreases while $U$ grows. Similar but much weaker
decreasing of $\Delta S_{\rm max}$ is found for DMFT results. The account of
local quantum fluctuations results in larger values of $\Delta S_{\rm max}$
within DMFT than within MFA. A peak width of $\Delta S (T)$ at half height is
approximately the same for both methods. Another effect of DMFT local quantum
fluctuations is the destruction of anomalous Curie temperature $T_C$ dependence
on $U$ present in MFA, which is invoked by an effect of giant van Hove
singularity. However the relative cooling power (RCP) is very close in DMFT and
MFA for the same model parameters and goes down upon $U$ increase.

Strongly Correlated Electrons