Magnetocaloric effect and magnetic ordering in GdFe 1- x T x Si, T = Cr, V, Ni

The intermetallic compounds GdFe Cr Si, = 0-0.8, GdFe V Si, = 0-0.4, and GdFe Ni Si, = 0-0.4 with a tetragonal CeFeSi ( ) structure type have been synthesized. The Curie temperature, , sharply increases from 130 K to 255 K and 250 K for the GdFe Cr Si and GdFe V Si compounds and decreases to 104 K for GdFe Ni Si. Within the framework of the model of effective d-f exchange interaction in 3̄d intermetallics, these changes in can be caused by the corresponding changes in the density of states. The electronic structure, magnetic moments and types of magnetic orderings of the GdFe T Si, T = Cr, V, Ni intermetallic compounds were calculated using the DFT+U theoretical method. For the GdFe Ni Si system, the transformation of a ferromagnet with the composition = 0 into an antiferromagnet with the composition = 0.3 was established experimentally and using first-principles calculations. The correlation of the ferromagnetic or antiferromagnetic type of the magnetic state in the GdFe Ni Si compounds with the value of the lattice parameter to greater or less than the critical value = 6.72 Å for the GdCoSi antiferromagnet has been experimentally established. The magnetic structures of the antiferromagnets GdFe Ni Si and GdCoSi were found to be different. GdFe Ni Si is characterized by a collapse in the magnetocaloric effect a change in the isothermal magnetic entropy Δ ( ). The compounds GdFe Cr Si with -Δ ( ) = 2.37 J kg K at = 255 K and = 82.07 J kg and GdFe V Si with -Δ ( ) = 2.06 J kg K at = 250 K and RC = 96.02 J kg in a field changing to 17 kOe could be of practical interest due to the being close to room temperature.