Hall effect and electrical resistivity of Tb75-Gd25 near the Curie point

2014 Fairly detailed and accurate data is presented for the Hall resistivity (03C1H), temperature derivative (d03C1H/dT), electrical resistivity (p), and derivative d03C1/dT in a ferromagnetic Tb75-Gd25 polycrystalline alloy, over a wide range of temperatures (77-360 K). Magnetic susceptibility data (~) 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 (03C1oH) and the extraordinary (03C1sH) terms are obtained, with the corresponding Hall constants (R0, Rs). Very sharp anomalies are observed both in d03C1/dT and d03C1H/dT in the transition region, indicative of a well defined critical point in our concentrated random magnetic alloy. The critical analysis shows that (1/03C1c). (d03C1/dT)±= (A±/03B1). (1 |03B5|-03B1) + B±, with 03B5 = (T Tc)/Tc, and (+) (-) means T > Tc, T Tc, respectively. We obtain, Tc = 244.79 K, 03B1_ = 03B1+ = 0.001, A+ /A_ ~ 0.88, over the range 1.2 x 10-4 03B5 0.7 x 10-2 and 6.2 x 10-3 |03B5| 2.6 10-2. For d03C1H/dT the situation is complex, due to the effect of the applied magnetic field. Our analysis shows the existence of important fluctuation effects near Tc, 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 03C1sH in Tb75-Gd25 can be accounted for in terms of a Kondo (skew and sidejump) 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. J. Physique 45 (1984) 779-789 AVRIL 1984,