Magnetocaloric effect in the ferromagnetic GdNi4M M Al, Si and antiferromagnetic NdNiAl4 compounds

Magnetocaloric MCE effect has been studied in the ferromagnetic FM GdNi4Al, GdNi4Si, and the antiferromagnetic AFM NdNiAl4 compounds. All the compounds order magnetically between 9 and 30 K. The maximum magnetic entropy change Delta S M is in the range of 10 16 J kg 1 K 1 for the studied RNi4M compounds. Arrott plots suggest that the phase transition in GdNi4Al and GdNi4Si may be of a first order type. It is ascribed to a field induced AFM FM transition. Neutron diffraction experiments on NdNiAl4 show that its magnetic structure is not of a simple AFM type. Additionally, the specific heat measurements for NdNiAl4 reveal a change of the sign of MCE and very small values of Delta S M and the adiabatic temperature change Delta T ad. C 201