Showing papers by "John B Ketterson published in 1970"

Velocity of Sound, Density, and Grüneisen Constant in Liquid He 4

Abstract: By measuring the pressure dependence of the velocity of sound, we have determined both the pressure dependence of the density and the Gr\"uneisen constant $u$ of liquid $^{4}\mathrm{He}$. Measurements were made below 0.1 K and in the vicinity of 0.5 K. Our determinations of the pressure dependence of the density agree quite well with that determined by Boghosian and Meyer, who used a capacitance bridge. Since the latter results rely on the validity of the Clausius-Mossotti relation and a pressure-independent electric polarizability, the present work can be interpreted as supporting both of these assumptions. We found that $u({\ensuremath{\rho}}_{0})\ensuremath{\equiv}(\frac{\ensuremath{\rho}}{c})\frac{\mathrm{dc}}{d\ensuremath{\rho}}=2.84$ under the vapor pressure at 0.1 K. Using this value of $u$ to calculate the attenuation of sound according to a three-phonon mechanism, we obtain an attenuation of less than half the measured value. Thus, the present theory of sound attenuation must be incomplete.

de Haas-van Alphen Effect in Platinum

Abstract: The de Haas-van Alphen effect has been used to study the extremal areas, cyclotron masses, and spin-splitting zeros on all three sheets of the Fermi surface of platinum. For the T-centered electron surface and $X$-centered hole pocket, newly developed inversion techniques have been employed to obtain the Fermi radius and Fermi velocity at all points on these surfaces. By performing the appropriate integrations over these surfaces, we have been able to determine the number of carriers and the density of states for these surfaces. Our observations on the open-hole surface, when combined with band-structure calculations, confirm the shape and connectivity of this surface. By combining effective-mass data with spin-splitting zero data, we have obtained information on the magnitude and anisotropy of the $g$ factor on all surfaces. In general, we find the $g$ factor to be different from 2.0 and quite anisotropic. The effective-mass measurements, when compared with band-structure calculations, indicate an enhancement of approximately 30%.

Low-Temperature Negative-Ion Mobility in Liquid 3 He

Abstract: The negative-ion mobility in liquid $^{3}\mathrm{He}$ has been determined in the range 17-300 mK. The pressure dependence of the mobility up to 2 atm was also studied.

Negative ion transmission through the3He-4He phase boundary

Abstract: A potential barrier is observed for the transmission of electron bubbles through the3He-4He boundary of a phase-separated mixture from the4He-rich side. The origin of the barrier is electrostatic (dielectric image charge) but the measured magnitude is considerably less than a simple estimate predicts. The reason for this discrepancy is explained in terms of a finite boundary width.

g Factor and Exchange Splitting in Pure Pd and Pt and Cobalt‐Doped Pd

Abstract: The anisotropy of the g factor on all sheets of the Fermi surface of pure Pt and Pd has been investigated by studying the spin splitting amplitude vanishing of the de Haas‐van Alphen effect. In all cases the g factor was observed to be anisotropic and varied by as much as 25% from its free space value of 2. Thus, estimates of the Stoner enhancement factor deduced from the calculated density of states with a g factor of 2 may be in considerable error. Evidence for the itinerant nature of the ferromagnetism in cobalt‐doped palladium has been observed both from the disappearance of the expected spin splitting zeros and the beating of the frequencies derived from corresponding cross‐sectional areas on the exchange split bands. An estimate of the magnitude of the exchange splitting is made from the beat frequency.

Accurate orientation method for dHvA data

Abstract: A new technique for improving the accuracy of the angular orientation of nonsymmetry plane dHvA data on cubic systems by an order of magnitude (from 2.0° to 0.2°) has been developed. The extension of this technique to orienting dHvA data in noncubic crystallographic systems, or to orienting data for other types of experiments, viz. neutron scattering, should be straightforward.