Contribution of energy-gap in the ferromagnetic spin-wave spectrum on magnetocaloric parameters of CeRu(2)Ge(2).

A study of the magnetocaloric effect has been performed on a polycrystalline CeRu(2)Ge(2) compound, which exhibits an antiferromagnetic ordering below T(N) = 8.3 K and enters into a ferromagnetic ground state at T(C) = 7.4 K. The origins of the magnetocaloric parameters (the isothermal entropy change: -ΔS and the adiabatic temperature change: ΔT(ad)) of the CeRu(2)Ge(2) compound below T(C) have been analyzed. A sharp decrease in -ΔS has been observed below T(C). However, the ΔT(ad) does not fall as sharply as -ΔS with decreasing temperature in the corresponding temperature region. This behavior results in an additional value of ΔT(ad) at low temperature, which originates from the exponential decrease of the magnetic contribution of specific heat associated with an increase of energy-gap in the ferromagnetic spin-wave spectrum with the application of magnetic field.