Oral: Employing Weron’s probabilistic approach to probe the slow-spin dynamics of the tri-cation spinel ZnGeCoO₄

Altering the long-range magnetic ordering in spinels (AB₂O₄) via substitution by 3d-transition metals at the tetrahedral (A) and/or octahedral (B) lattice sites often induce magnetic frustration. As a result, a frustration-induced cluster spin-glass (SG) state may emerge at low temperatures. Here, we report a highly frustrated cubic spinel (Fd-3m) ZnGeCoO₄ (ZGCO) which is a derivative of GeCo₂O₄, synthesized by the solid-state route. Only 50% of the B sites being occupied by magnetic cations Co²⁺ renders the system to be of short-range magnetic order. The frequency and field dependence of the ac-susceptibility of ZGCO established a ‘hierarchically organized’ cluster-glass state using dynamical scaling laws, namely the Power and the Vogel-Fulcher laws. The SG state was further confirmed by a detailed analysis of the temporal variation of its isothermal remanent magnetization (IRM). Mathematical fits of the non-exponential IRM tail to well-known relaxation functions including the semi-logarithmic function, power law, etc., were obtained. Karina Weron’s probabilistic function, formulated on the basis of a purely stochastic model, is the best in reproducing the IRM data of ZGCO [J. Phys. Condens. Matter, 3,9151 (1991)]. Slow spin-dynamics and non-exponential critical response of the SG state in ZGCO has been established in the present study.