Anomalous Magnetic Contributions to Hall Effect in Ho0.5Lu0.5B12

Strongly correlated electron system Ho0.5Lu0.5B12 possesses a cooperative dynamic Jahn-Teller instability of the boron cage that affects the rattling modes of loosely bound rare-earth ions, a frustrated antiferromagnetic (AF) ground state and dynamic charge stripes. The Hall effect, resistivity, and magnetization were studied on the single crystals of this AF metal (T-N approximate to 3.4 K) at temperatures 1.9-4.2 K in magnetic field B <= 7 T applied along the principal axis of the fcc lattice. Two components of anomalous Hall effect (AHE) were identified on Hall resistivity rho(H)(B) curves. The first AHE component to be proportional to magnetization is detected both in the AF and in the paramagnetic state of Ho0.5Lu0.5B12. The second one that contributes to AHE only in the AF phase has the amplitude increasing with lowering of temperature. Both AHE components are strongly anisotropic having maximal amplitudes for B parallel to (100). The observed AHE features are discussed in terms of spin chirality and Berry phase effects, which could develop in the exotic spin texture of Ho0.5Lu0.5B12 under strong charge carrier scattering on dynamic charge stripes.