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

• 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.

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 Hf0.825Ta0.175Fe2 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 Hf0.825Ta0.175Fe2, 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.