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

LiMn_2−XZn_XO₄ (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 Fdm to P2₁3 in the spinel oxide, while those with a small substitution degree (X<0.1) had Fdm 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 4.48μ_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.