Large remanent magnetization in Bi doped CaMn7O12 compounds: Magnetic and X-ray absorption spectroscopic studies

Abstract

The structural and magnetic properties of Bi doped CaMn7O12 (CMO) multiferroics are correlated with the results of electronic structures obtained from X-ray absorption spectroscopy. These compounds were prepared by using wet sol–gel technique and their X-ray diffraction patterns confirm the single phase formation. The solid solubility limit of Bi in CMO is found to be 10% at Ca site. A remarkable enhancement in magnetization is observed for 10% Bi doped Ca1-xBixMn7O12. This increase in remanence magnetization is ~10 times in comparison to CMO. Doping of divalent Ca ions by trivalent Bi ions cause an increase in trivalent Mn ions and hence increase in unpaired electrons leading to this enhancement of magnetization. The X-ray absorption studies at the O K-, and Mn K-, and Mn L3,2 -edges of Ca1-xBixMn7O12 (x = 0, 0.05 and 0.10) clearly indicate an increase in the ratio of Mn3+/Mn4+ along with increase in interstitial oxygen atoms. This significant increase in magnetic remanence for optimum Bi doping is very promising for magnetic and microwave applications.