Structural and magnetic properties of frustrated Ga^sub x^Mn^sub (3-x)^O^sub 4^(1.2 = x = 1.6) spinels

We report a systematic study of the structural and magnetic properties of frustrated compounds of GaxMn(3−x)O4 (1.2 ≤ x ≤ 1.6) prepared by solid-state reaction. Using Rietveld refinement of X-ray diffraction patterns and O'Neill-Navrotsky model, we demonstrate that the system GaxMn(3−x)O4 (1.2 ≤ x ≤ 1.6) is an inverse spinel with low inversion parameter, in which Ga3+ replaces Mn3+ cations located in B-sites. The inverse magnetic susceptibility, the shape of ZFC/FC magnetization curves at low temperatures, the existence of hysteresis in all compounds, the frustration parameter and the spontaneous magnetization analysis show that the compounds with x = 1.2–1.4 exhibit a non-collinear ferrimagnetic order and the compounds with x = 1.5–1.6 exhibit a frustrated non-collinear ferrimagnetic order. Spin wave stiffness parameters were determined for each composition using the fitting results of spontaneous magnetization curves. It is demonstrated that for the compounds x = 1.2–1.4 with a non-frustrated ferrimagnetic order, the change of spontaneous magnetization Ms(T) obeys to Bloch's law (T3/2). For x = 1.5–1.6, the compounds exhibit a frustrated ferrimagnetic order, and the Ms(T) shows a deviation from Bloch's law.