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P-wave scattering effects on ultrasonic attenuation in dirty superconductors
Vol. 5, No. 6
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
x 10~cycles/sec. The Debye temperature, calculated from the elastic constant data, is 141 ~ 4°K.
transition metals of the second and third series. The case of nickel and palladium is then discussed more accurately.
(Received 20 March 1967) (Revised 21 April 1967) 16.
P-WAVE SCATTERING EFFECTS ON ULTRASONIC A~~ENUATION IN DIRTY SUPERCONDUCTORS A. Houghton and F. B. McLean (Department of Physics, Brown University, Providence, R. I.)
We have calculated the coefficients of ultrasonic absorption in dirty superconductors for small energy gap taking into consideration both s-wave and p-wave scattering of the electrons by impurities, (Received 6 March 1967) 17.
INFLUENCE DU COUPLAGE SPIN ORB1TE SUR LA SUSCEPTIBILITE MAGNETIQUE DES METAUX DE TRANSITION P. Lenglart (Facultd des Sciences Physique des Solides, 91 Orsay, France)
On se propose d’étudier, dans l’approximation des liaisons fortes, l’influence du couplage spin-orbite sur Ia susceptibilitd magnétique des métaux de transition et sur Ia stabilitd de l’état paramagnétique. On montre que l’énergie d’ échange intraatomique est equivalente a 1’ existence d’un champ moldculaire if intervenant que sur Ia partie due au spin du moment magnetique de bande; par ailleurs, ce moment magnetique est notablement réduit par le mélange des états de spins. Ii semble que cette reduction joue un role important pour rendre compte de l’absence d’ordre magnetique dans le cas des métaux des seconde et troisième series de transition. On discute ensuite plus en detail les cas du Nickel et du Palladium, The effect of spin orbit coupling on the magnetic susceptibility oftransition metals and on the stability of the paramagnetic state is studied in the tight binding approximation. It is shown that the intraatomic exchange energy is equivalent to a molecular field acting only on the spin part of the band magnetic moment; otherwise this magnetic moment Is notably reduced by the spin state mixing. It appears that this reduction plays an important part to explain the absence of magnetic order in the
v
(Received 30 March 1967) (Revised 10 April 1967) 18.
SLOW CONDUCTWITY RELAXATION IN BULK GERMANIUM CONTAINING OXYGEN E. Athchi (Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo, Japan)
In oxygen-doped n-germanium, heat-treated at 300°C, slow conductivity relaxations have been observed over the temperature range about 210-300°K; they occur after not only photoexcitation but also thermal excitation, namely the excitation by rapidly cooling or heating a sample. Their time constants range between a fraction of a second and two hours. The time constant of the conductivity relaxation for cooltag and the time constant for heating agree well with the time constant of the photoconductivity relaxation, and, therefore, It is suggested that there is a common rate-limiting process among these relaxation processes. It is concluded that the slow relaxation phenomena occur in bulk germanium and are associated with oxygencomplex (probably Ge*02 ). (Received 7 April 1967) 19.
DIRTY SUPERCONDUCTORS AND ISOTOPE E FFECT G. Gusman
The isotope effect in transition metal superconductors is reexamined. The approximate calculations of Garland are shown to be qualitatively justifiable in the limit of sufficient dirtiness, i. e., w ~ ‘ T>> F . Here ~iiDis the Debye frequency, F the Fermi energy of electrons and T the relaxation time of electrons due to impurity scattering. Furthermore a necessary condition for Garland’s calculation to be valid is that the effective mass ratio md* /m,* be not greatly in excess of unity. If this condition is violated, which appears to be the case in such alloys as Nb 3Sn, than a modification ensues wherein the cut-off of Garland corresponding to the band width is replaced by the d band plasma frequency. (Received 27 February 1967)
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
x 10~cycles/sec. The Debye temperature, calculated from the elastic constant data, is 141 ~ 4°K.
transition metals of the second and third series. The case of nickel and palladium is then discussed more accurately.
(Received 20 March 1967) (Revised 21 April 1967) 16.
P-WAVE SCATTERING EFFECTS ON ULTRASONIC A~~ENUATION IN DIRTY SUPERCONDUCTORS A. Houghton and F. B. McLean (Department of Physics, Brown University, Providence, R. I.)
We have calculated the coefficients of ultrasonic absorption in dirty superconductors for small energy gap taking into consideration both s-wave and p-wave scattering of the electrons by impurities, (Received 6 March 1967) 17.
INFLUENCE DU COUPLAGE SPIN ORB1TE SUR LA SUSCEPTIBILITE MAGNETIQUE DES METAUX DE TRANSITION P. Lenglart (Facultd des Sciences Physique des Solides, 91 Orsay, France)
On se propose d’étudier, dans l’approximation des liaisons fortes, l’influence du couplage spin-orbite sur Ia susceptibilitd magnétique des métaux de transition et sur Ia stabilitd de l’état paramagnétique. On montre que l’énergie d’ échange intraatomique est equivalente a 1’ existence d’un champ moldculaire if intervenant que sur Ia partie due au spin du moment magnetique de bande; par ailleurs, ce moment magnetique est notablement réduit par le mélange des états de spins. Ii semble que cette reduction joue un role important pour rendre compte de l’absence d’ordre magnetique dans le cas des métaux des seconde et troisième series de transition. On discute ensuite plus en detail les cas du Nickel et du Palladium, The effect of spin orbit coupling on the magnetic susceptibility oftransition metals and on the stability of the paramagnetic state is studied in the tight binding approximation. It is shown that the intraatomic exchange energy is equivalent to a molecular field acting only on the spin part of the band magnetic moment; otherwise this magnetic moment Is notably reduced by the spin state mixing. It appears that this reduction plays an important part to explain the absence of magnetic order in the
v
(Received 30 March 1967) (Revised 10 April 1967) 18.
SLOW CONDUCTWITY RELAXATION IN BULK GERMANIUM CONTAINING OXYGEN E. Athchi (Central Research Laboratory, Hitachi Ltd., Kokubunji, Tokyo, Japan)
In oxygen-doped n-germanium, heat-treated at 300°C, slow conductivity relaxations have been observed over the temperature range about 210-300°K; they occur after not only photoexcitation but also thermal excitation, namely the excitation by rapidly cooling or heating a sample. Their time constants range between a fraction of a second and two hours. The time constant of the conductivity relaxation for cooltag and the time constant for heating agree well with the time constant of the photoconductivity relaxation, and, therefore, It is suggested that there is a common rate-limiting process among these relaxation processes. It is concluded that the slow relaxation phenomena occur in bulk germanium and are associated with oxygencomplex (probably Ge*02 ). (Received 7 April 1967) 19.
DIRTY SUPERCONDUCTORS AND ISOTOPE E FFECT G. Gusman
The isotope effect in transition metal superconductors is reexamined. The approximate calculations of Garland are shown to be qualitatively justifiable in the limit of sufficient dirtiness, i. e., w ~ ‘ T>> F . Here ~iiDis the Debye frequency, F the Fermi energy of electrons and T the relaxation time of electrons due to impurity scattering. Furthermore a necessary condition for Garland’s calculation to be valid is that the effective mass ratio md* /m,* be not greatly in excess of unity. If this condition is violated, which appears to be the case in such alloys as Nb 3Sn, than a modification ensues wherein the cut-off of Garland corresponding to the band width is replaced by the d band plasma frequency. (Received 27 February 1967)