No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
THE PHONON SOFTENING IN METALLIC FINE PARTICLES
Abstract
La résistance électrique des films des petites particules Ag et Al a été mesurée entre 1,5 et 300 K. L'augmentation de la température de transition de supraconduction et la réduction de la température de Debye ont été obtenues et on suggère l'existence d'un phonon mou venant de la surface dans tout le domaine de température. The d.c. electrical resistance of films of Ag and Al fine particles was measured between 1.5 and 300 K. The enhancement of the superconducting transition temperature and the reduction of the Debye temperature were obtained and they suggest the existence of the phonon softening due to the surface in the whole temperature region.
Electron spin resonance (e.s.r.) spectra of small particles (ca. 500 nm) of sodium and potassium metals have been recorded over the temperature range 4-100 K. Analysis of the e.s.r. lineshapes yields values of the electron spin-lattice relaxation rate T-1_1. Both electron spin relaxation and electrical resistivity in the alkalis are governed by the scattering of high velocity conduction electrons by lattice phonons. The temperature dependence of T-1_1 bears a striking similarity to that of the electrical resistivity. In both cases the temperature dependence is adequately described by a Bloch-Gruneisen function for temperatures above 1/2theta, where theta is the Debye temperature. If a Debye model is used to approximate the behaviour of lattice vibrational modes, the derived Debye temperatures from the spin relaxation data are about 20% lower in the particulate samples of sodium and potassium than in the corresponding bulk metals.
Electrically conducting films of thickness 2 m have been prepared on ordinary glass slides by growing ultra-fine particles of iron and copper, respectively, from a suitable precursor sol. The diameters of metal particles can be varied from 3–13 nm by controlling the heat-treatment schedule of the sol coating. Resistivity measurements (d.c.) have been carried out over the temperature range 80–300 K. The resistivity values in the range 0.0001–0.0039 cm have been obtained depending on the particle diameter and the type of metal used. The effective Debye temperature D for the different nanoparticle systems have been estimated by fitting the experimental data to the Ziman equation. D is found to vary from 346–408 K for iron with the particle size in the range 3.4–9.5 nm. The values obtained for copper are 243–307 K with particle diameters covering a range of 5.9–12.6 nm.
- K Fujita
- T Wada
- N Yoshioka
- H Hauser
- J J Uyeda
OHSHIMA, K., FUJITA, T., WADA, N., YOSHIOKA, H. and [6] HAUSER, J. J., Phys. Rev. B 3 (1971) 1611.
UYEDA, R., J. Phys. Soc. Japan 26 (1969) 862.
[7] DEUTSCHER, G. and PASTERNAK, M., Phys. Rev. B 10 (1974)
- T Ohshima
FUJITA, T., OHSHIMA, K. and KUROISHI, T., J. Phys. Soc. [5] STRONGIN, M. and KAMMERER, 0. F., J. Appl. Phys 39
Japan 40 (1976) 90.
(1968) 2509.
- J W Bennemann
- F M Ohshima
- K Kuroishi
GARLAND, J. W., BENNEMANN, K. H. and MUELLER, F. M., [8] OHSHIMA, K., KUROISHI, T. and FUJITA, T., to be published
Phys. Rev. Lett. 21 (1968) 1315.
in J. Phys. Soc. Japan.