Electronic transport in ferromagnetic alloys and the Slater-Pauling curve

Abstract

Experimental measurements of the residual resistivity ͑x͒ of the binary-alloy system Fe 1−x Cr x have shown anomalous concentration dependence which deviates significantly from Nordheim's rule. In the low ͑x Ͻ 10%͒ Cr concentration regime the resistivity has been found to increase linearly with x until Ϸ10% Cr where the resistivity reaches a plateau persisting to Ϸ20% Cr. In this paper we present ab initio calculations of ͑x͒ which explain this anomalous behavior and which are based on the Korringa-Kohn-Rostoker method in conjunction with the Kubo-Greenwood formalism. Furthermore we are able to show that the effects of short-range ordering or clustering have little effect via our use of the nonlocal coherent-potential approximation. For the interpretation of the results we study the alloy electronic structure by calculating the Bloch spectral function particularly in the vicinity of the Fermi energy. From the analysis of our results we infer that a similar behavior of the resistivity should also be obtained for iron-rich Fe 1−x V x alloys-an inference confirmed by further explicit resistivity calculations. Both of these alloy systems belong to the same branch of the famous SlaterPauling plot, and we postulate that other alloy systems from this branch should show a similar behavior. Our calculations show that the appearance of the plateau in the resistivity can be attributed to the dominant contribution of minority-spin electrons to the conductivity which is nearly unaffected by the increase in Cr/V concentration x, and we remark that this minority-spin electron feature is also responsible for the simple linear variation in the average moment in the Slater-Pauling plot for these materials.

Coherent potential approximation as a voltage probe

“…The coherent potential of the system can be found by self-consistently solving Eq. (19). The Green's function of the sample, connected to the electrodes within the CPA, is given by Eq.…”

Electronic and transport properties of disordered transition‐metal alloys

“…It follows that other late TM-rich alloys should behave similarly. In sharp contrast studies of systems containing no late transition metals, e.g., Cu 1-x Zn x [76] and Fe 1-x Cr x [101], found no decrease of residual resistivity with increase in SR-clustering.…”

“…Obviously, the conductivity is quite different for the two spin channels. This behavior can be traced back straight forwardly to the electronic structure of the alloy system around the Fermi energy [101]. The analysis in Section 7 above has shown, there exists a well-defined Fermi surface for the spin down subsystem.…”

“…The resistivity of the alloys Fe 1-x Cr x and Fe 1-x V x was investigated recently to study the impact of the ferromagnetic ordering in these prototype systems as well as the importance of possible short-range order [101]. The main results of these calculations are shown in Fig.…”

Influence of complex disorder on skew-scattering Hall effects inL10-ordered FePt alloy

“…Indeed, from our full calculations we find that majority electrons constitute most of the conductivity, resulting in a 50% spinpolarization of the diagonal conductivity. Such a strong difference in the influence of disorder on transport properties of majority versus minority electrons is very common in magnetic materials, and is responsible for e.g., an anomalous concentration dependence of the resistivity of Fe upon alloying with Cr or V [31]. On the contrary, the LDOS of a Pt impurity deviates around the Fermi energy considerably from the substituted host-Fe atom in both spin channels [cf.…”