Resistivity Measurements In Magnetic Fields Research Articles

MAGNETORESISTIVITY BEHAVIOR OF SOME DILUTE Cu–Fe, Gu–Mn, AND Gu–Zn ALLOYS AT LIQUID HELIUM TEMPERATURES

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.