Magnetic properties of hole-doped SCGO, SrCr₈Ga _4xM_xO₁₉ (M=Zn, Mg, Cu)

We report changes in the magnetic properties of hole-doped SCGO, SrCr ₈Ga₄O₁₉, induced by replacing non-magnetic Ga³⁺ with both non-magnetic (Mg²⁺ and Zn²⁺) and magnetic (Cu²⁺) cations. The resulting solid solutions, SrCr ₈Ga_4xM_xO₁₉ (M=Zn, Mg, Cu) have been studied by x-ray diffraction and magnetic susceptibility measurements. For all cases, at least 10% of Ga can be replaced by divalent cations resulting in oxidation of 5% of the Cr³⁺ (d³) to Cr⁴⁺ (d²). The hole doping results in an increase in ferromagnetic interactions and reduces the magnetic frustration. In the SrCr ₈Ga_4xCu_xO₁₉ series an enhancement of the spin-glass-like transition is observed, T_f 6K, which we ascribe to the magnetic nature of the Cu²⁺ (d⁹) dopant.