Orientation dependence of the anomalous Hall resistivity in single crystals of Yb14MnSb11

The Hall resistivity, electrical resistivity, and magnetization of single crystals of the tetragonal ferromagnet Yb14MnSb11 are reported as a function of the direction of the current I and magnetic field H with respect to the principal crystallographic axes. With I along the unique c direction and H in the a-b plane, the anomalous Hall resistivity in the limit of zero applied field is negative for all temperatures T TC=53 K. In this direction, the anomalous Hall effect behaves in a manner similar to that observed in other ferromagnets such as Fe, Co, Mn5Ge3, and EuFe4Sb12. However, with I in the a-b plane and H along the c direction, the anomalous Hall behavior is completely different. The anomalous Hall resistivity data are positive for all T TC and a similar analysis of these data fails. In this direction, the anomalous response is not a simple linear function of the magnetization order parameter, and for a fixed temperature, T TC does not depend on the magnitude of the magnetization perpendicular to the current in the a-b plane. That is, when the magnetization and applied field are rotated away from the c direction, the anomalous Hall resistivity does not change. In all other soft ferromagnets that we have examined including La doped crystals of Yb14MnSb11, i.e., Yb13.3La0.7MnSb11 , rotation of the magnetization and magnetic field by an angle away from a direction perpendicular to I results in a decrease in both the anomalous and normal portions of the Hall resistivity that approximately scales as cos . We suggest that the unique response exhibited by Yb14MnSb11 is a direct reflection of the delicate balance between ferromagnetism and Kondo screening.