EXPANSIVITY AND HEAT-CAPACITY DATA FOR LU AND SC CRYSTALS FROM 1 TO 300 K - SPIN-FLUCTUATION AND ELECTRON-PHONON EFFECTS

Linear thermal expansivity (alpha) measurements from 1 to 300 K and he at capacity (C-p) measurements from 1 to 110 K are reported for single crystals of the hexagonal scandium and lutetium metals; the C, data w ere combined with previous data to obtain smooth representations to 30 5 K for Lu and 350 K for Sc. The Theta(0)'s (352 and 190 K, respective ly, for Sc and Lu) and gamma's (10.38 and 8.30 mJ/mol K-2, respectivel y for Sc and Lu) are in reasonable agreement with previous data of var ious kinds. Electronic contributions are much larger for the alpha's t han for the C-p's, with the large anisotropies of the alpha's primaril y electronic in origin. The equivalent Debye Theta's for the lattice C -p's and the Gruneisen parameters Gamma for the lattice alpha's both s how an unexpected T dependence at ''high'' T (T greater than or simila r to Theta(0)/2), which can be associated with the disappearance of sp in-fluctuation and electron-phonon enhancements to the electronic prop erties; this effect has been reported previously for Sc C-p's by Plesc hiutschnig et al. [Phys. Rev. B 44, 6794 (1991)]. While the resulting high-temperature ''bare'' or ''density of states'' gamma for Sc, gamma (b)=5.75(25) mJ/mol K-2, is slightly larger than that calculated recen tly by Gotz and Winter [J, Phys. Condens. Matter 5, 1721 (1993)], the magnitude of the sum (gamma(spin)+gamma(ep)) agrees well. For Lu, for which no recent calculations exist, gamma(b)=5.50(25) mJ/mol K-2. The various Gamma's (a and c axis, lattice, and electronic) generally are quite anisotropic, with no obvious correlation between high- and low-T behavior. The anisotropy in Gamma which is associated with the enhanc ement (spin plus e-p) contribution is very large, with similar magnitu des for the c-axis values (similar to 17), but + for Lu and - for Sc. A 186-at. ppm Fe impurity in the scandium crystals makes a significant contribution to all of the data below 3.5 K. The resulting impurity G amma's are very large and very anisotropic (Gamma(a)(Fe)=-40, Gamma(c) (Fe)=30).