Synthesis and magnetic properties of Li-Mn-Zn spinel oxides

LiMn2-XZnXO4 (X<0.5) compounds were prepared by sol-gel method. The specimens with a large substitution degree (X>0.2) led to symmetry reduction from Fd (3) over barm to P2(1)3 in the spinel oxide, while those with a small substitution degree (X<0.1) had Fd<(3)over bar>m cubic symmetry. The Zn2+-substitution led to the enhancement of the low-temperature magnetic susceptibility and a shift in the Weiss constant from negative to positive, indicating that the dominant exchange interaction changed from antiferromagnetic to ferromagnetic. For the compounds with X=0.5, the spontaneous magnetization was 4.48 mu(B) and the Curie temperature was approximately 21 K. The experimentally obtained magnetization value was close to the value calculated under the assumption that the spins of the Mn4+ ions were aligned in ferromagnetic form. In addition, the magnetic properties of Li-Mn-Zn spinel oxides were briefly discussed, and compared with those of Li-Mn-M (M=Ni, Mg) spinel oxides. (C) 2010 Elsevier B.V. All rights reserved.