| Hall effect and electrical resistivity of Tb75-Gd25 near the Curie point (1984) | |||||||||||||||
Abstract | |||||||||||||||
| Fairly detailed and accurate data is presented for the Hall resistivity (ρH), temperature derivative (dρH/dT), electrical resistivity (p), and derivative dρ/dT in a ferromagnetic Tb75-Gd25 polycrystalline alloy, over a wide range of temperatures (77-360 K). Magnetic susceptibility data (χ) near and above the Curie point is also included. The different contributions to the electrical resistivity are separated out, including the spin-disorder, residual and phonon terms, the results being compared with theory. For the Hall resistivity, the normal (ρoH) and the extraordinary (ρs H) terms are obtained, with the corresponding Hall constants (R 0, Rs). Very sharp anomalies are observed both in dρ/dT and dρH/dT in the transition region, indicative of a well defined critical point in our concentrated random magnetic alloy. The critical analysis shows that (1/ρc). (dρ/dT)±= (A±/α). (1 - |ε|-α) + B±, with ε = (T - Tc)/Tc, and (+) (-) means T > Tc, T < Tc, respectively. We obtain, Tc = 244.79 K, α_ = α+ = - 0.001, A+ /A_ ≃ 0.88, over the range 1.2 x 10-4 < ε < 0.7 x 10-2 and 6.2 x 10-3 < |ε| < 2.6 × 10 -2. For dρH/dT the situation is complex, due to the effect of the applied magnetic field. Our analysis shows the existence of important fluctuation effects near T c, as given by the derivative dRs/dT. The extraordinary Hall resistivity in Tb75-Gd25 is extensively analysed here, in order to separate out the different contributions, i.e. the skew and side-jump terms, including the effects of several possible scattering Hamiltonians (Kondo, Smit). We show that ρsH in Tb75-Gd 25 can be accounted for in terms of a Kondo (skew and side-jump) and a side-jump Smit contribution. Finally, the Curie temperature of Tb75-Gd25 is related to the transition points of Tb and Gd, using the theory of binary rare earth random magnetic alloys. | |||||||||||||||
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