Search for magneto-flicker noise in K

Abstract

A search has been made for a magnetic field-dependent flicker noise in potassium, predicted by the charge-density-wave (CDW) model of the alkali metals. The search was made in high-purity encapsulated K wires over 1 m long with diameters 0.023 and 0.010 in. The specimens were prepared by degassing high-purity K, vacuum filling long thin plastic (0.023-in. i.d.) or cupro-nickel (0.010-in. i.d.) tubing with molten K, and using a temperature gradient for controlled solidification. Four-terminal magnetoresistance measurements were made of the encapsulated K wires in transverse and longitudinal magnetic fields up to 44 kG. The search for the magneto-flicker noise was made up to 44-kG fields and 1.5-A d.c. currents. No magneto-flicker noise was found from 10 Hz to 10 kHz greater than or equal to 4 nV, which is the minimum detectable noise signal. The nonobservance of the magneto-flicker noise in the plastic-encapsulated samples of 0.023-in. i.d. indicates a discrepancy ∼ ${10}^6$ in the mean-square noise voltage of the magneto-flicker noise, as predicted by the original CDW model. An analysis of the data on the cupro-nickel-encapsulated samples of 0.010-in. i.d. indicates that the samples have voids with a total length ∼ 1% of the sample length and thin K films (∼ 1.5 μm thick) connecting the K regions separated by the voids. The nonobservance of the magneto-flicker noise in these thin films indicates a discrepancy ∼ ${10}^3$ in the mean-square noise voltage of the magneto-flicker noise, as predicted by the revised CDW model.