  Heusler alloys are widely studied due to their interesting structural and
magnetic properties, like magnetic memory shape ability, coupled
magneto-structural phase transitions and half-metallicity; ruled, for many
cases, by the valence electrons number ($N_v$). The present work focuses on the
magnetocaloric potentials of half-metals, exploring the effect of $N_v$ on the
magnetic entropy change, preserving half-metallicity. The test bench is the
Si-rich side of the half-metallic series Fe$_2$MnSi$_{1-x}$Ga$_x$. From the
obtained experimental results it was possible to obtain $|\Delta
S|_{max}=\Delta H^{0.8}(\alpha+\beta N_v)$, i.e., the maximum magnetic entropy
change depends in a linear fashion on $N_v$, weighted by a power law on the
magnetic field change $\Delta H$ ($\alpha$ and $\beta$ are constants
experimentally determined). In addition, it was also possible to predict a new
multifunctional Heusler alloy, with enhanced magnetocaloric effect, Curie
temperature close to 300 K and half-metallicity.
