Magnetocaloric effect and magnetic ordering in GdFe1-xTxSi, T = Cr, V, Ni

The intermetallic compounds GdFe1-xCrxSi, x = 0-0.8, GdFe1-xVxSi, x = 0-0.4, and GdFe1-xNixSi, x = 0-0.4 with a tetragonal CeFeSi (P4/nmm) structure type have been synthesized. The Curie temperature, T-C, sharply increases from 130 K to 255 K and 250 K for the GdFe1-xCrxSi and GdFe1-xVxSi compounds and decreases to 104 K for GdFe1-xNixSi. Within the framework of the model of effective d-f exchange interaction in R3d intermetallics, these changes in T-C can be caused by the corresponding changes in the density of states. The electronic structure, magnetic moments and types of magnetic orderings of the GdFe1-xTxSi, T = Cr, V, Ni intermetallic compounds were calculated using the DFT+U theoretical method. For the GdFe1-xNixSi system, the transformation of a ferromagnet with the composition x = 0 into an antiferromagnet with the composition x = 0.3 was established experimentally and using first-principles calculations. The correlation of the ferromagnetic or antiferromagnetic type of the magnetic state in the GdFe1-xNixSi compounds with the value of the lattice parameter c to greater or less than the critical value c = 6.72 angstrom for the GdCoSi antiferromagnet has been experimentally established. The magnetic structures of the antiferromagnets GdFe0.7Ni0.3Si and GdCoSi were found to be different. GdFe0.7Ni0.3Si is characterized by a collapse in the magnetocaloric effect via a change in the isothermal magnetic entropy Delta S-M(T-C). The compounds GdFe0.4Cr0.6Si with -Delta S-M(T-C) = 2.37 J kg(-1) K-1 at T-C = 255 K and R-C = 82.07 J kg(-1) and GdFe0.7V0.3Si with -Delta S-M(T-C) = 2.06 J kg K-1 at T-C = 250 K and RC = 96.02 J kg(-1) in a field changing to 17 kOe could be of practical interest due to the T-C being close to room temperature.

Automated summary

Intermetallic compounds GdFe1-xCrxSi, GdFe1-xVxSi, and GdFe1-xNixSi with a tetragonal CeFeSi structure type have been synthesized and their properties studied. The changes in Curie temperature can be attributed to changes in the density of states. The electronic structure, magnetic moments, and magnetic orderings of these compounds were calculated using a theoretical method. The transformation of GdFe1-xNixSi from a ferromagnet to an antiferromagnet was observed experimentally and confirmed by calculations. The compounds GdFe0.4Cr0.6Si and GdFe0.7V0.3Si with their Curie temperatures close to room temperature could be of practical interest.