Relation between structure and magnetism of TixFe100−x alloys within the C14 Laves-phase stability range

We report about X-ray and magnetic investigations on polycrystalline alloys with hexagonal C14 (MgZn₂) structure of the system Ti_xFe_100−x in the concentration range 30.5x36.5 around the Laves-phase composition TiFe₂ (Ti_33.3Fe_66.6). Neighboring compositions Fe₅₀Ti₅₀ (with B2 structure) and Ti₁₅Fe₈₅ and Ti₂₀Fe₈₀ (with BCC structure) have also been investigated. From the data we establish a magnetic phase diagram for the C14 range of the system, showing a rather sharp transition from mainly ferromagnetic ordering in the range x<32 to a mainly antiferromagnetic ordering in the range x>32. The results can be made plausible microscopically by taking the site dependence of the moments into account. A revised structural equilibrium phase diagram is also given.