Cross over between ferro and antiferromagnetic order in Fe itinerant electron magnetism: An experimental and theoretical study of the model (Hf,Ta)Fe₂ Laves phases

Highlights: • a lattice parameter is found to drive the change from FM to AF magnetic order. • We demonstrate the strong interplay between crystal structure and magnetic order. • Fe magnetic moment is very sensitive to change of the lattice constant a. • A metamagnetic phase transition has been observed. - Abstract: Band structure calculations are reported to describe the effects of Ta for Hf substitution on the electronic structure of the Laves phase of HfFe₂. According to experimental results emphasis is put on the investigation of the Hf_0.825Ta_0.175Fe₂ composition in comparison with the reference HfFe₂ and TaFe₂ compounds. By investigation of the theoretical interatomic exchange interactions constants, we showed the influence of the magnetovolume effect on the magnetic phase stability for one intermediate composition Hf_0.825Ta_0.175Fe₂, chosen in the most interesting part of the magnetic phase diagram with coexistence of ferromagnetic (FM) and antiferromagnetic (AF) behaviour. Evolution of the a lattice parameter is found to drive the change from FM to AF magnetic order. A detailed study of the interatomic Fe–Fe exchange coupling constants and their lattice dependence reveals that the ferromagnetic interaction with the first shell is strongly reduced upon contraction of the a lattice parameter