Spin-glass state in CuGa2O4

Abstract

Magnetic susceptibility, magnetization, specific-heat, and positive muon spin relaxation (µSR) measurements have been used to characterize the magnetic ground state of the spinel compound CuGa2O4. We observe a spin-glass transition of the S=1/2 Cu2+ spins below Tf = 2.5 K characterized by a cusp in the susceptibility curve which is suppressed when a magnetic field is applied. We show that the magnetization of CuGa2O4 depends on the magnetic history of the sample. Well below Tf, the muon signal resembles the dynamical Kubo-Toyabe expression reflecting that the spin freezing process in CuGa2O4 results in a Gaussian distribution of the magnetic moments. By means of Monte Carlo simulations, we obtain the relevant exchange integrals between the Cu2+ spins in this compound. © 2001 The American Physical Society.