Hall coefficient behavior in TiFe, TiCo, TiNi, and their alloys

摘要: Abstract Hall coefficient and resistivity measurements on the 3d transition metal compounds TiFe, TiCo, TiNi, several of their alloys, were made at 295°, 77°, 4.2°K. These materials contain between 6 7 valence electrons per atom (Nve). The behavior was characterized by values as large +35 × 10−4 cm3/C (in TiFe), a strong temperature dependence all compositions studied, and, with increasing Nve, changes in sign from positive to negative back again. Negative coefficients have not been observed before this range Nve any other materials. discussion showed, first all, that phenomenological two-band model could account qualitatively for data Nve. It also demonstrated small group carriers present exceeding 1 40 number, which had room-temperature mobility greater than 122 cm2/V-sec, it shown conclusion did depend number bands actually present. Secondly, Mattheiss's theoretical band calculation non-magnetic Cr, Mo, W contained specific feature—a maximum wave function surprisingly p-like (rather d-like) character—which high-mobility holes TiFe. then applied remainder data, difficult say four responsible major features experimental data. Finally, comparison results earlier Cr its alloys (Nve 5.9 6.6) revealed distinctive differences temperature- composition coefficient. explained using Lomer's proposal antiferromagnetic ordering fourband considerably lower carrier concentration. assumed chemical TiFe has essentially same effect, effect related different ways magnetic two sets concluded weak-field studies elements compounds, can be quite useful, especially cases where low mobilities lack single-crystal samples prevent application sophisticated, high field techniques. This is due fact more sensitive realized numbers cross Fermi level.