Nature of Electrical Resistivity of the Ferromagnetic Metals at Low Temperatures

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Abstract
The study of the resistivity of nickel, iron, and nickel-copper alloys with copper concentration up to 25%, at temperatures from 2°K to 78°K, has been carried out. The empirical formulas for resistivity in this temperature range have been found. It has been shown that the ``phonon'' term in T5 does not play an essential role in the resistance of ferromagnetic metals at temperatures up to 20–30°K, but that it contributes to the resistance above these temperatures. The values of (ρ-ρ0)/n for nickel and iron [where ρ and ρ0 are the resistivity and residual resistivity at 0°K, respectively, n=(T/θ)32 is the ``magnon'' concentration, θ is the exchange parameter in Bloch's 32 law], and the value of Δρ/Δn for nickel (where Δρ is the change of resistivity, Δn=ΔIs/I0 is the decrease of magnon concentration, and ΔIs is the increase of true magnetization in strong magnetic field) have been found and compared with each other. It has been shown that both of these values for nickel are of the same order and also the same order as the value of Δρ0/ν, where Δρ0 is the increase of residual resistivity of nickel copper alloys with the concentration, ν, of copper in these alloys. The coincidence of the above-mentioned values is considered to be an indirect proof for the assumption that the temperature dependent part of the resistance of ferromagnetic metals at low temperatures is related to the scattering of electrons by magnon.