  Magnetocaloric effect in a double-tetrahedral chain, in which nodal lattice
sites occupied by the localized Ising spins regularly alternate with three
equivalent lattice sites available for mobile electrons, is exactly
investigated by considering the one-third electron filling and the
ferromagnetic Ising exchange interaction between the mobile electrons and their
nearest Ising neighbours. The entropy and the magnetic Gruneisen parameter,
which closely relate to the magnetocaloric effect, are exactly calculated in
order to investigate the relation between the ground-state degeneracy and the
cooling efficiency of the hybrid spin-electron system during the adiabatic
demagnetization.
