R. C. Richardson

Properties of melting 3He: Specific heat, entropy, latent heat, and temperature

A sequence of experiments has been performed to measure thermal properties of liquid and solid 3He between the temperatures 1 and 25 mK at melting curve densities. A two-phase mixture of 3He sample was self-cooled by the Pomeranchuk method. A heat pulse technique was used, combined with measurements of pressure and volume, to yield separate determinations of liquid and solid properties: the specific heat of liquid 3He in the normal Fermi liquid and superfluid phases; the entropy of solid 3He above and through a nuclear magnetic transition at 1.10 mK; and an absolute thermodynamic temperature scale based on measurement of latent heat of conversion of liquid to solid.

Spin-wave phenomena in liquid3He systems

AbstractThe magnetic effects predicted by Leggett and Rice for Fermi liquids in the collisionless regime have been verified. Spin-echo measurements are reported which demonstrate the existence of spin waves and undamped spin currents in liquid3He and dilute3He-4He solutions. The experimental results are compared with the theoretical expressions of Leggett and Rice, and values of the Fermi liquid interaction parameter

Viscosity measurements in superfluid 3He-B from 2 to 29 bar

\lambda = \left[ {1/(1 + F_0^a )} \right] - \left\{ {1/[1 + (F_1^a /3)]} \right\}

Magnetic coupling of3He with a fluorocarbon substrate

are derived for three samples: liquid3He atP=0 and 27 atm, and a 6.4%3He-4He solution. In addition, some techniques for direct observation of individual spin-wave modes are explored and the results reported.

Attenuation of zero sound and the several low-temperature phases of liquid3He

Nuclear magnetic relaxation studies of isotopically impure solid4He have been made in the temperature-independent region of the relaxation spectrum, below 0.7 K. The Torrey theory for nuclear relaxation has been applied to measurements ofT1 andT2 to calculate the characteristic fluctuation time of the3He atoms due to the zero-point motion of3He and4He atoms. The fluctuation rates have been determined as a function of molar volume and Larmor frequency in samples where the mole fractions of3He in the gaseous mixtures used to form the solids were 0.02, 0.01, 0.005, and 0.002. The volume dependence of the fluctuation rate has been found to be far greater than that of the exchange rate of a3He-3He pair.T1 has been found to vary as ω02, and bothT1 andT2 increased as the concentration decreased, in agreement with the Torrey theory. Preliminary investigations of the solid isotopic phase separation have also been carried out.

The low temperature viscosity of normal liquid3He

Measurements from a high-Q torsional oscillator and a vibrating wire are presented which give a consistent view of the viscosity of the normal fraction of 3He-B at high pressure. At low pressures discrepancies are largely eliminated by taking into account a mean-free-path size effect. We compare our corrected viscosities with recent calculations. The superfluid fraction, also measured in this experiment, is reexamined in the light of recent specific heat measurements.

Determination of the electric field gradient and relaxation time measurements in scandium metal at very low temperature

Measurements have been made of the normal fluid fraction of superfluid3He-B at eight different pressures between 0 and 29.2 bar. The minimum temperatures were such that ρn/ρ was reduced to less than 0.5%. The experiments, carried out independently at Cornell and Texas A&M Universities, used similar Andronikashvilli-type torsional oscillators. The results are qualitatively similar, but show significant differences due to the use of different temperature standards. Both sets of results are presented in tabular form. The inconsistencies in the temperature scales preclude the examination of the results for possible strong coupling effects.

Magnetic surface phenomena in liquid 3He

We observe a nuclear interaction between3He and the19F spin species of a fluorocarbon substrate. The magnetization of a3He film is strongly linked to that of the19F substrate spins. We use this interaction as a probe of the3He to identify several features important in surface relaxation.