Ab Initio-Calculations of Residual Resistivities For Dilute Ni-Alloys
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AB INITIO-CALCULATIONS OF RESIDUAL RESISTIVITIES FOR DILUTE NI-ALLOYS
I.MERTIG Technische Universitit Dresden, Institut ffir Theoretische Physik, Mommsenstr. 13, 0-8027 Dresden, Germany R.ZELLER and P.H.DEDERICHS Institut ffir Festk6rperforschung der Kernforschungsanlage Jiilich, D-5170 Jiilich, Germany
ABSTRACT We report about residual resistivity calculations for dilute Ni alloys which are based on density-functional theory and the Korringa-Kohn-Rostoker Green's-function method. The transport is described quasiclassically by means of the Boltzmann equation using a two current model for the ferromagnetic host. In particular we consider 3d, 4d, 4sp and 5sp impurities in Ni and include in addition to the impurity atom one shell of perturbed host atoms in the calculation. For the residual resistivity satisfactory agreement with the experiments is obtained in practically all cases. We clarify the role of both subbands for the transport properties. INTRODUCTION Following Mott's idea (1] several transport properties of ferromagnetic alloys can be explained by assuming conduction in parallel by electrons in the majority bands (spin-up electrons) and by electrons in the minority bands (spin-down electrons) . The physical basis of this two current model is the dominance of spin conserving-scattering and the weakness of spin-flip collisions in a ferromagnetic alloy at low temperatures. This model has been used by many authors [2,3,4,5,6,7,8,10] for studies on Ni based alloys. It seems that the model provides a good basis for the discussion of a wide range of alloy properties [9]. Owing to the developments of density-functional theory and sophisticated numerical techniques we are now able to perform realistic ab - initio calculations and we are in a position to check the reliability of such model studies mentioned above. Recent theoretical studies of dilute Ni alloys by Bliigel and co-workers (1987) [11], by Stefanou and co-workers (1987)[12] and by Zeller (1987) [131 presented a detailed analysis of the range of charge and magnetization perturbations around impurities in Ni, performed within the Korringa-Kohn-Rostoker (KKR) Green's function method. This work is an extension of the same formalism to transport properties of dilute Ni alloys. For this purpose the microscopic transition probability for an impurity atom with perturbed neighboring potentials around the impurity is calculated and feeded into the Boltzmann equations for the spin-up and the spin-down electrons. The transport equation was then solved by iteration as proposed by Coleridge (1972) [14] and van Ek and Lodder (1990) [15] for nonmagnetic materials. Within this scheme a detailed analysis of the spin-up and spin-down contributions to the residual resistivity becomes feasible without introducing any free parameters.
Mat. Res. Soc. Symp. Proc. Vol. 253. ý,1992 Materials Research Society
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MICROSCOPIC TRANSITION PROBABILITY The transition from a state k into a state k', where k is a shorthand notation for the wave vector k and the bandindex v, is given
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