Contribution of energy-gap in the ferromagnetic spin-wave spectrum on magnetocaloric parameters of CeRu2Ge2

A study of the magnetocaloric effect has been performed on a polycrystalline CeRu2Ge2 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: -Delta S and the adiabatic temperature change: Delta T-ad) of the CeRu2Ge2 compound below TC have been analyzed. A sharp decrease in -Delta S has been observed below TC. However, the Delta T-ad does not fall as sharply as -Delta S with decreasing temperature in the corresponding temperature region. This behavior results in an additional value of Delta T-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.