Magnetic Ordering of CoCl_{2}-GIC: a Spin Ceramic -Hierarchical Successive Transitions and the Intermediate Glassy Phase-

TL;DR

This study investigates the complex magnetic phase transitions in CoCl₂-GIC, revealing hierarchical ordering, spin glass behavior, and coexistence of different glassy regions through detailed magnetization relaxation analysis.

Contribution

It provides new insights into the dynamical properties and coexistence of glassy phases in a spin ceramic with hierarchical magnetic transitions.

Findings

Hierarchical successive magnetic transitions at T_{cu} and T_{cl}.

Change in relaxation rate behavior indicating coexistence of two glassy regions.

Evidence of complex spin glass dynamics between T_{cu} and T_{cl}.

Abstract

Stage-2 CoCl$_{2}$-GIC is a spin ceramic and shows hierarchical successive transitions at $T_{cu}$ (= 8.9 K) and $T_{cl}$ (= 7.0 K) from the paramagnetic phase into an intra-cluster (two-dimensional ferromagnetic) order with inter-cluster disorder and then to an inter-cluster (three-dimensional antiferromagnetic like) order over the whole system. The nature of the inter-cluster disorder was suggested to be of spin glass by nonlinear magnetic response analyses around $T_{cu}$ and by studies on dynamical aspects of ordering between $T_{cu}$ and $T_{cl}$. Here, we present a further extensive examination of a series of time dependence of zero-field cooled magnetization $M_{ZFC}$ after the aging protocol below $T_{cu}$. The time dependence of the relaxation rates $S_{ZFC}(t) = (1/H)dM_{ZFC}(t)/d\ln t$ dramatically changes from the curves of simple spin glass aging effect below $T_{cl}$ to those of two peaks above $T_{cl}$. The characteristic relaxation behavior apparently indicates that there coexist two different kinds of glassy correlated regions below $T_{cu}$.