Low-Temperature Resistivity Minima and Negative Magnetoresistivities in some Dilute Superconducting Ti Alloys

Electrical resistivities in the range 1.1 to 35°K and magneto-resistivities in the range 1.1 to 4.2°K have been measured in a number of dilute, superconducting hcp Ti alloys. Resistivity minima occurring between 14 and 18°K are observed in ≈99.92% pure Ti, and in Ti-Mn alloys with Mn concentrations between 0.02 and 2.0 at.% (nominal atomic percent). Negative magneto-resistivities between 2.6 and 7.2% at 30 kG and 4.2°K are observed in Ti-Mn alloys with Mn concentrations between 0.1 and 2.0 at.%. The absolute magnitude of the negative magnetoresistance increases as temperature decreases for $T_s<T<\mathrm{}4.2\mathrm{}°$K, where $T_s$ is the temperature at which the zero-field resistivity begins to decrease due to the onset of supercouductivity. Field- and temperature-dependent Hall coefficients are observed at liquid helium temperatures in Ti containing Mn concentrations of 1.0 and 2.0 at.%. Ti alloys containing 1.2 at.% Cr and 0.96 at.% Fe display resistivity minima at about 17°K, but, unlike Ti-Mn alloys, they have small positive magnetoresistivities and do not exhibit field-dependent Hall coefficients at 4.2°K. Neither negative magneto-resistivities nor significant resistivity minima are observed in Ti containing 1.3 at.% Co, 1.0 at.% Ni, 1.1 at.% Al, or 1.0 at.% Nb. Considered in the light of recent ideas regarding the origin of the low-temperature resistive anomalies, the data suggest that localized magnetic moments exist in dilute superconducting Ti alloys containing Cr, Mn, and Fe, and that the conduction electrons interact with these moments.