Element substitution effects on magnetism of cadmium chromite spinel CdCr₂O₄

Cadmium chromite spinel CdCr₂O₄ is a geometrically-frustrated magnet with the Neel temperature T_N ~ 8 K, and the Weiss temperature q_w ~ -70 K. The magnetic properties of this compound are fully dominated by the orbital-inactive Cr³⁺ (3d³) with spin S = 3/2 residing on the pyrochlore network. To study the element substitution effects on the geometrically-frustrated magnetism of CdCr₂O₄, we investigate structural and magnetic properties of polycrystalline Cd(Cr_1-xFe_x)₂O₄,Cd(Cr_1-xV_x)₂O₄, and Cd(Cr_1-xMn_x)₂O₄. For these mixed crystals, the substituted Fe³⁺ (3d⁵) with S =5/2 is an orbital-inactive ion, but V³⁺ (3d²) with S = 1 and Mn³⁺ (3d⁴) with S = 2 are orbital-active ions. The experiments reveal that the antiferromagnetic order of CdCr₂O₄ is sensitively suppressed by the element substitutions, and instead, the spin-glass-like behavior appears at low temperatures below ~ 10 K. This result implies the competition of geometrical and bond frustrations in Cd(Cr_1-xFe_x)₂O₄, Cd(Cr_1-xV_x)₂O₄, and Cd(Cr_1-xMn_x)₂O₄.