Magnetoresistivity Behavior of some Dilute Cu-Fe, Cu-Mn, and Cu-Zn Alloys at Liquid Helium Temperatures

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Resistance measurements in magnetic fields up to 100 kilo-oersteds have been made on some Cu-Fe, Cu-Mn, and Cu-Zn alloys in the liquid helium temperature range, where the Cu alloys containing paramagnetic impurities exhibit resistance anomalies. The sign of both the transverse and longitudinal magnetoresistivity in Cu-Fe alloys at 4.2°K is positive for alloys containing less than 0.04 at. % Fe and negative for alloys containing more than this concentration of iron. For all of the Cu-Fe alloys studied the magnitude of the magnetoresistance normalized to the zero-field resistivity is larger at 4.2°K than at lower temperatures. The sign of both the transverse and longitudinal magnetoresistivity in a Cu-0.007 at. % Mn alloy at 4.2°K is positive for all magnetic field values. However, at lower temperatures (1.3°K) the same alloy has a negative magnetoresistivity at low fields, which saturates and becomes positive at higher field values. The rate of change of the normalized transverse and longitudinal magnetoresistivity for Cu-Mn is also larger at 4.2°K than at lower temperatures. The magnetoresistivity of the Cu-Zn alloys decreases with decreasing field strength and increasing Zn concentration, with a modified Kohler law fitting the experimental data. The transverse magnetoresistivity is always larger than the longitudinal one, and for the most dilute Cu-Zn alloy the magnitude of both components is of the same order as that of pure Cu. It is found possible empirically to separate the Cu-Mn magnetoresistivity data into a positive and negative component ; however, for the Cu-Fe alloys studied the present analysis proves the existence of a negative component for the more concentrated alloys but does not permit a separation from the total magnetoresistivity effect.

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