Doping effects on itinerant-electron magnetism of Laves compound AFe₂ (A = Ti and Zr)

Laves compounds TiFe₂ and ZrFe₂ have C14-type hexagonal and C15-type cubic crystal structures, respectively. C14-type hexagonal crystal structure of TiFe₂ contains Kagome lattice sheets of Fe atoms. C15-type cubic crystal structure of ZrFe₂ contains Fe sublattice of corner-sharing tetrahedra (pyrochlore lattice). TiFe₂ and ZrFe₂ both exhibits itinerant-electron magnetism, where Fe 3d electrons are expected to play dominate role. While ZrFe₂ exhibits a ferromagnetic transition at T_C ~ 620 K, TiFe₂ exhibits an antiferromagnetic transition at T_N ~ 290 K. To study doping effects on the itinerant-electron magnetism of TiFe₂ and ZrFe₂, we investigate structural, electric, and magnetic properties of polycrystalline Ti(Fe_1-xCo_x)₂ and Zr(Fe_1-xCo_x)₂. The experiments reveal that, for Zr(Fe_1-xCo_x)₂, the ferromagnetic order is suppressed with increasing Co concentration x. On the other hand, Ti(Fe_1-xCo_x)₂ is found to exhibit a variety of antiferromagnetic and ferromagnetic orders depending on Co concentration x.