Deviations from Matthiessen's rule and resistivity saturation effects in Gd and Fe from first principles

Abstract

According to earlier first-principles calculations, the spin-disorder contribution to the resistivity of rare-earth metals in the paramagnetic state is strongly underestimated if Matthiessen's rule is assumed to hold. To understand this discrepancy, the resistivity of paramagnetic Fe and Gd is evaluated by taking into account both spin and phonon disorder. Calculations are performed using the supercell approach within the linear muffin-tin orbital method. Phonon disorder is modeled by introducing random displacements of the atomic nuclei, and the results are compared with the case of fictitious Anderson disorder. In both cases the resistivity shows a nonlinear dependence on the square of the disorder potential, which is interpreted as a resistivity saturation effect. This effect is much stronger in Gd than in Fe. The non-linearity makes the phonon and spin-disorder contributions to the resistivity non-additive, and the standard procedure of extracting the spin-disorder resistivity by extrapolation from high temperatures becomes ambiguous. An "apparent" spin-disorder resistivity obtained through such extrapolation is in much better agreement with experiment compared to the results obtained by considering only spin disorder. By analyzing the spectral function of the paramagnetic Gd in the presence of Anderson disorder, the resistivity saturation is explained by the collapse of a large area of the Fermi surface due to the disorder-induced mixing between the electronic and hole sheets.

Heat Flow in Earth's Core From Invariant Electrical Resistivity of Fe‐Si on the Melting Boundary to 9 GPa: Do Light Elements Matter?

“…The value of ρ is almost identical to that of pure liquid Fe (within uncertainties) above 6 GPa (Figure ). This behavior is unexpected as it violates Matthiessen's rule (Glasbrenner et al, ). That is, additional resistivity arising from the Si impurity component that Matthiessen's rule predicts is not observed.…”

Physical properties of FeRh alloys: The antiferromagnetic to ferromagnetic transition

“…It is not generally correct [39], but we have verified its validity in the present FeRh alloy by performing resistivity calculations for the AFMII FeRh alloy assuming (i) Imz = 10 −3 Ry without the spin disorder (y = 0), (ii) Imz = 10 −5 Ry with the spin disorder (y = 0.05), and (iii) Imz = 10 −3 Ry and the same spin disorder as in (ii). The finite Imz is a rough model of the disorder due to phonons (although there is no relation to a certain temperature).…”

“…A possible effect of phonons at a given temperature can be eventually simulated by adding a small finite Imz. In this case, the combined effect of spin and phonon disorders is treated beyond a simple Matthiessen rule [39].…”

Electrical resistivity of substitutionally disordered hcp Fe–Si and Fe–Ni alloys: Chemically-induced resistivity saturation in the Earth's core

“…Since electrons in the vicinity of the Fermi level are only effective to electron transport properties (Banhart et al, 1989;Glasbrenner et al, At low, but finite, impurity concentrations (e.g. Fig 5 a-c), one can find that the cross section still has distinguishable features of the Fermi surface of host metal.…”