Tuning of magnetic properties in Cr-doped lithium ferrite

Abstract

Cationic substitutions in lithium ferrite spinel (LiFe 5 O 8 ) leading to modifications in magnetic properties have a significant role in their technological applications. In this context, LiFe 5− x Cr x O 8 , compounds with 0 ≤ x ≤ 3 were synthesized and studied using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), M o ¨ ssbauer spectroscopy and magnetization measurements. Oxidation states of Fe and Cr are found to be 3 + from XPS investigations and further confirmed from the M o ¨ ssbauer analysis. Cr replaces Fe from both tetrahedral and octahedral sites. Magnetization and magnetic ordering temperature decrease with increasing Cr concentration. This is consequent to reduced strength of dominant Fe - O - Fe interactions due to replacement of Fe with Cr cation possessing relatively smaller magnetic moment. The positive value of Curie-Weiss constant implies that the system has dominant ferromagnetic interactions. The much important negative magnetization and spin compensation phenomena are observed only in specific range of doping concentration (x = 2.5–3). Spin compensation in LiFe 2.5 Cr 2.5 O 8 occurs at 315 K, close to room temperature. • The effect of Cr doping on oxidation state of cations and their distribution at tetrahedral and octahedral sites is reported. • The influence of Cr doping on the magnetic properties of LiFe 5 O 8 is reported. • Spin compensation behavior is observed in LiFe 2.5 CR 2.5 O 8 and LiFe 2 CR 3 O 8 compounds.