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.
@article{arxiv.2010.13291,
title = {Cluster glass transition and relaxation in random spinel CoGa2O4},
author = {T. Naka and T. Nakane and S. Ishii and M. Nakayama and A. Ohmura and F. Ishikawa and A. de Visser and H. Abe and T. Uchikoshi},
journal= {arXiv preprint arXiv:2010.13291},
year = {2021}
}