Chemical control of spin chirality in (Nd_1-xDy_x) ₂Mo₂O₇

Magnetization and Hall resistivity have been investigated for single crystals of Dy-doped Nd₂Mo₂O₇. A sharp decrease of the Hall resistivity upon a metamagnetic transition, perhaps associated with magnetic-field (H) induced flop of Dy³⁺ moments, has been observed in the Dy-doped crystals only for H||[111] direction. In addition, the sign of the Hall resistivity at a high field, both for H||[100] and for H||[111], changes with the Dy doping. These results are explained in terms of the sign change of Mo spin chirality that is controlled by the Dy³⁺ moments with a different sign of f-d interaction from the Nd³⁺ moments.