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Effect of chromium substituted on structural and magnetic characterization lithium ferrite nanoparticles

In this work, we present a structural, morphology and magnetic study of the Li0.5Fe2.5-xCrxO4 spinel nanoparticles (x = 0, 0.5, 0.75, 1, and 1.25) with mean particle size of 20-30 nm prepared by sol-gel method. The lattice constants and the size of particle decrease with increasing Cr concentration. In these samples, the preference of Cr3+ and Li+ ions in the octahedral sites and a small degree of site-interchange between Li+ in the octahedral sites and Fe3+ in the tetrahedral sites were found which increases with increasing the Cr content. | Vietnam Journal of Chemistry, International Edition, 55(4): 521-526, 2017 DOI: 10.15625/2525-2321.2017-00502 Effect of chromium substituted on structural and magnetic characterization lithium ferrite nanoparticles Nguyen Thi Lan1*, Phuong Dinh Tam1, Nguyen Phuong Duong2, Than Duc Hien2 1 Advanced Institute for Science and Technology, Hanoi University of Science and Technology (HUST) 2 International Training Institute for Materials Science, HUST Received 16 June 2017; Accepted for publication 28 August 2017 Abstract In this work, we present a structural, morphology and magnetic study of the Li0.5Fe2.5-xCrxO4 spinel nanoparticles (x = 0, 0.5, 0.75, 1, and 1.25) with mean particle size of 20-30 nm prepared by sol-gel method. The lattice constants and the size of particle decrease with increasing Cr concentration. In these samples, the preference of Cr3+ and Li+ ions in the octahedral sites and a small degree of site-interchange between Li+ in the octahedral sites and Fe3+ in the tetrahedral sites were found which increases with increasing the Cr content. A decrease of magnetization due to the spin disorder in the surface layer of the particles was observed. The spontaneous magnetization at 5K suggests the Néel type of magnetic ordering in these samples. The magnetic coercivity is discussed in terms of particle size, morphology and chromium substitution. Keywords. Chromium substitution, sol-gel method, nanoparticles, lithium ferrite. 1. INTRODUCTION Lithium ferrite Li0.5Fe2.5O4 possesses high saturation magnetization, high Curie temperature and soft magnetic hysteresis loop. For a long time it has continuously been interested for application in the fields of low-cost microwave devices, memory cores [1, 2] and for cathode materials in rechargeable lithium batteries [3]. Li0.5Fe2.5O4 is an inverse spinel with the Li+ and the three-fifths of the Fe3+ ions occupying the octahedral B sites of the cubic spinel structure of the general formula AB2O4. The rest of the .