Anomalous Hall effect in three ferromagnetic compounds:EuFe4Sb12,Yb14MnSb11, andEu8Ga16Ge30

The Hall resistivity ({rho}{sub xy}), resistivity ({rho}{sub xx}), and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe{sub 4}Sb{sub 12} (T{sub c}{approx}84 K), Yb{sub 14}MnSb{sub 11} (T{sub c}{approx}53 K), and Eu{sub 8}Ga{sub 16}Ge{sub 30} (T{sub c}{approx}36 K) are Zintl compounds with carrier concentrations between 1 x 10{sup 21} and 3.5 x 10{sup 21} cm{sup -3}. The relative decrease in {rho}{sub xx} below T{sub c} [{rho}{sub xx}(T{sub c})Y{rho}{sub xx}(2 K)] is 28, 6.5, and 1.3 for EuFe{sub 4}Sb{sub 12}, Yb{sub 14}MnSb{sub 11}, and Eu{sub 8}Ga{sub 16}Ge{sub 30}, respectively. The low carrier concentrations coupled with low magnetic anisotropies allow a relatively clean separation between the anomalous ({rho}{sub xy}), and normal contributions to the measured Hall resistivity. For each compound the anomalous contribution in the zero field limit is fit to a{rho}{sub xx}+{sigma}{sub xy}{rho}{sub xx}{sup 2} for temperatures T<T{sub c}. At T=0 the anomalous Hall conductivity {sigma}{sub xy}{sup 0}, is -220 {+-} 5 ({Omega}{sup -1} cm{sup -1}), -14.7 {+-} 1 ({Omega}{sup -1} cm{sup -1}), and 28 {+-} 3 ({Omega}{sup -1} cm{sup -1}) for EuFe{sub 4}Sb{sub 12}, Yb{sub 14}MnSb{sub 11}, and Eu{sub 8}Ga{sub 16}Ge{sub 30}, respectively, and is independent of temperature for T<T{sub c}more » if the change in spontaneous magnetization (order parameter) with temperature is taken into account. These data are consistent with recent theories of the anomalous Hall effect that suggest that even for stochiometric ferromagnetic crystals, such as those studied in this article, the intrinsic Hall conductivity is finite at T=0, and is a ground state property that can be calculated from the electronic structure.« less