Quaternary spinel oxide LiMn1.825Cr0.175O4 Powder was synthesized by using an ultrasonic spray pyrolysis method, without additional annealing. The crystal structure of the as-prepared powder was revealed by X-ray powder diffraction and identified as a single spinel phase with Fd3m space group. The powders had a spherical morphology with extremely smooth surface appearance and densely congested interior structure. Transmission electron microscopy confirmed that the particle consisted by the cohesion of the primary particles. Magnetic measurements performed in DC field in both zero-field-cooled and field-cooled regimes, as well as AC susceptibility experiments, show that system undergoes spin-glass transition at the freezing temperature T-f = 20 K. The value of the effective magnetic moment mu(eff) = 4.34 mu(B) Obtained from the Curie-Weiss fit in the high temperature region confirms the substitution of Mn3+ ions with Cr3+ ions. (C) 2006 Elsevier Ltd. All rights reserved.