Cluster glass transition and relaxation in random spinel CoGa2O4

TL;DR

This study investigates the magnetic properties and glass transition behavior of the random spinel CoGa2O4, revealing a spin-glass transition at 8.2 K and complex relaxation dynamics indicative of glassy states.

Contribution

It provides detailed experimental evidence of spin-glass transition and relaxation mechanisms in CoGa2O4, highlighting the effects of random ion distribution on magnetic glassy behavior.

Findings

Spin-glass transition at 8.2 K confirmed by susceptibility measurements

Relaxation time follows Vogel-Fulcher law, indicating glassy dynamics

Magnetic entropy reduction suggests cluster formation above TSG

Abstract

We report magnetic properties in the random spinel magnet CoGa2O4. Rietveld analysis of the x-ray diffraction profile for CoGa2O4 reveals that the Co and Ga ions are distributed randomly in the tetrahedral A-sites and octahedral B-sites in the cubic spinel structure. CoGa2O4 exhibits a spin-glass transition at TSG = 8.2 K that is confirmed by measurements of the dc- and ac-susceptibilities and thermoremanent magnetization (TRM) that develops below TSG. From the frequency dependence of the freezing temperature Tf for CoGa2O4, it is indicated that the relaxation time follows a Vogel-Fulcher law. Magnetic entropy is considerably reduced, probably because magnetic cluster formation developed even at T > TSG. The relaxation rate of TRM is considerably enhanced at TSG and decays rapidly above and below TSG. The time course of TRM is reproduced by non-exponential relaxation forms, such as a stretched exponential (Kohlrausch) as well as Ogielski and Weron relaxation forms. This behavior is displayed universally in glass systems, and the characteristic parameters associated with these functions were reasonable.