Anomalous Hall effect in three ferromagnetic compounds: EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30

The Hall resistivity xy , resistivity xx , and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe4Sb12 Tc 84 K , Yb14MnSb11 Tc 53 K , and Eu8Ga16Ge30 Tc 36 K are Zintl compounds with carrier concentrations between 1 1021 and 3.5 1021 cm−3. The relative decrease in xx below Tc xx Tc / xx 2 K is 28, 6.5, and 1.3 for EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30, respectively. The low carrier concentrations coupled with low magnetic anisotropies allow a relatively clean separation between the anomalous xy , and normal contributions to the measured Hall resistivity. For each compound the anomalous contribution in the zero field limit is fit to a xx+ xy xx 2 for temperatures T Tc. At T=0 the anomalous Hall conductivity xy 0 , is −220±5 −1 cm−1 , −14.7±1 −1 cm−1 , and 28±3 −1 cm−1 for EuFe4Sb12, Yb14MnSb11, and Eu8Ga16Ge30, respectively, and is independent of temperature for T Tc if the change in spontaneous magnetization order parameter with temperature is taken into account. These data are consistent with recent theories T. Jungwirth, Q. Niu, and A. H. MacDonald, Phys. Rev. Lett. 88, 207208 2002 ; Y. Yao, L. Kleinman, A. H. MacDonald, J. Sinova, T. Jungwirth, D.-S. Wang, E. Wang, and Q. Niu, Phys. Rev. Lett. 92, 037204 2004 ; I. V. Solovyev, Phys. Rev. B 67, 174406 2003 ; Z. Fang, N. Nagosa, K. S. Takahashi, A. Asamitsu, R. Mathieu, T. Ogasawara, H. Yamada, M. Kawasaki, Y. Tokura, and K. Terakura, Science 302, 92 2003 ; and Y. Taguchi, Y. Oohara, H. Yoshizawa, N. Nagaosa, and Y. Tokura, Science 291, 2573 2001 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.