Structural and magnetic properties of Mg(In2-xMnx)O4 system

We synthesized the Mn-doped Mg(In2-xMnx)O-4 oxides with 0.03 <= x <= 0.55 using a solid-state reaction method. The X-ray diffraction patterns of the samples were in a good agreement with that of a distorted orthorhombic spinel phase. Their lattice parameters and unit-cell volumes decrease with x due to the substitution of the smaller Mn3+ ions to the larger In3+ ions. The undoped MgIn2O4 oxide presents diamagnetic signals for 5K <= T <= 300 K. The M(H) at T = 300 K reveals a fairly negative-sloped linear relationship. Neither magnetic hysteresis nor saturation behavior was observed in this parent sample. For the Mn-doped samples, however, positive magnetization were observed between 5 and 300 K even if the x value is as low as 0.03. The mass susceptibility enhances with Mn content and it reaches the highest value of 1.4 x 10(-3) emu/g Oe (at T = 300 K) at x = 0.45. Furthermore, the Mn-doped oxides with x = 0.06 and 0.2, respectively, exhibit nonlinear magnetization curves and small hysteretic loops in low magnetic fields. Susceptibilities of the Mn-doped samples are much higher than those of MnO2, Mn2O3 oxides, and Mn metals. These results show that the oxides have potential to be magnetic semiconductors. (C) 2006 Elsevier B. V. All rights reserved.