Nuclear Heat Capacity Research Articles

Calorimetric measurements of nuclear quadrupole interactions in tellurium-doped bismuth

By doping bismuth with tellurium to increase the charge carrier density and thus speed up the slow nuclear spin-lattice relaxation the nuclear quadrupole heat capacity becomes measurable in contrast to pure bismuth. The quadrupole heat capacity is greatly influenced by doping, increasing by 64% over the pure bismuth value on the addition of 0.23 at. % of tellurium. This results from a local asymmetric distortion of the valence electron states of the bismuth ions around the impurity site.

Magnetic Properties of Praseodymium in Magnetic Fields Determined from the Nuclear Heat Capacity and Applied to Nuclear Cooling

The nuclear heat capacity of praseodymium in fields from 0 to 18.6 kOe has been measured from 16 to 300 mK. In zero field the metal was found to be ordered with average magnetic moments of 0.62${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$ and 0.05${\mathrm{\ensuremath{\mu}}}_{\mathrm{B}}$ on the two inequivalent lattice sites. Above 10 kOe the Van Vleck behavior dominates and an induced moment appears on both sites. The corresponding induced hyperfine field has been employed for nuclear cooling.

Calorimetric Investigation of the Hyperfine Interactions in Metallic Nd, Sm, and Dy

The specific heats of metallic Nd, Sm, and Dy have been measured in the temperature range 0.025-0.4 K, where the nuclear (hyperfine) heat capacity predominates. The data are fitted to theoretical Schottky curves corresponding to a Hamiltonian of the form $H={a}^{\ensuremath{'}}{I}_{z}+P[I_{z}^{2}\ensuremath{-}\frac{1}{3}I(I+1)]$, where ${a}^{\ensuremath{'}}$ and $P$ are the magnetic dipole and electric quadrupole interaction parameters, respectively. The Nd data are consistent with a two-sublattice model with the electronic moments on each sublattice appreciably less than the full saturation value. Both the Sm and Dy data fit Schottky anomalies corresponding to the full saturated electronic moment on each ion.

Suppression of the Nuclear Heat Capacity in Bismuth Metal by Very Slow Spin-Lattice Relaxation, and a New Value for the Electronic Specific Heat

The specific heat of metallic bismuth has been measured from 0.05 to 0.8 K. The nuclear-quadrupole heat capacity expected from NMR measurements is not observed, allowing a more accurate determination of the electronic specific heat than has been possible previously. A lower limit for the nuclear spin-lattice relaxation time is estimated.

Calorimetric Investigation of Hyperfine Interactions in Metallic Ho and Tb

The specific heats of metallic Ho and Tb have been measured between 0.03 and 0.5\ifmmode^\circ\else\textdegree\fi{}K, a temperature range in which the nuclear (hyperfine) heat capacity predominates. The data are fitted with theoretical Schottky curves, using magnetic dipole hyperfine-interaction parameters ${a}^{\ensuremath{'}}=+0.319\ifmmode^\circ\else\textdegree\fi{}$K and ${a}^{\ensuremath{'}}=+0.149\ifmmode^\circ\else\textdegree\fi{}$K, and electric quadrupole coupling constants $P=+0.004\ifmmode^\circ\else\textdegree\fi{}$K and $P=+0.0158\ifmmode^\circ\else\textdegree\fi{}$K for Ho and Tb, respectively. For Tb, these values are in agreement with the parameters obtained from nuclear-magnetic-resonance measurements. An earlier suggestion by the present authors that a cooperative nuclear-nuclear interaction might be present in Tb is here shown to have been based on an erroneous temperature scale. A detailed description of the calorimeter is presented.

Molecular Rotation and Translation in Crystals. Nuclear Magnetic Resonance Absorption, Heat Capacity, and Entropy of Crystalline Solid Solutions of 2,2-Dimethylbutane in 2,3-Dimethylbutane from 10°K to 273°K

The nuclear magnetic resonance absorption of solid solutions of 2,2-dimethylbutane (A) and 2,3-dimethylbutane (B) has been studied as a function of composition. The melting range is clearly marked, but the rotational transition is absent. There is a maximum in the melting point diagram at the composition B2 A3. Thermal data have been determined on this complex from 10°K to 265°K from which the zero-point entropy has been deduced. The heat capacity curve and zero-point entropy of the crystals are those of a glass which indicates translational freedom in the rotating crystals.