Spin order-disorder evolution in spinel oxide series Zn(Fe,Ga)₂O_4.

The physics of spin glass remains interesting and unresolved since there exists no complete understanding of the influence of microscopic differences such as spin type, magnetic interaction, dimensionality, and electronic structure, on the spin glass state. Here we explore the relationship between the spin glass and the long-range antiferromagnetic order states in the Ga-substituted spinel Zn(Fe,Ga)₂O₄. By replacing Fe³⁺ ions with nonmagnetic Ga³⁺ ions at the B-site, a continuous evolution from the antiferromagnetic long-range order to a spin glass state is realized. The system experiences a fast lowering of heat capacity and magnetic susceptibility temperatures T_C and T_N with a few percents of Ga-doping. Further doping beyond 5% drives the system into a fully spin glass state. This evolution is explored by neutron magnetic diffuse scattering in detail. While the long-range antiferromagnetic ordered state exhibits both spin critical fluctuations around T_N and a well-defined wavevector (1, ½, 0), the spin glass state with 13% of Ga doping shows a broad distribution of spin correlation in the reciprocal space. A coexistence of short- and long-range orders is present at the intermediate range of 3% Ga doping. Our study provides a systematic exploration of differences between long-range order and spin glass behaviors in the fast relaxation time limit of sub-femtosecond scale.