Doping Effect of Cr3+ on Magnetic Properties and Structure Stability of NiFe2O4

Cr3+doping NiFe2O4was prepared by mixed ions co-precipitation.The magnetic properties were investigated by the physical propertymeasurement system.The saturationmagnetizationMs, remanentmagnetizationMrand coactivity Hcwere calculated from 5 K hysteretic loops of different Cr3+doping content NiFe2O4after being annealed at 350 and 600℃. With the increasing of Cr3+content, for 350℃annealing samples,Msdecreased from 32.49 to 18.11 emu/g, Mrdecreased from 9.39 to 3.72 emu/g andHcincreased from 230 to 2500 Oe, for 600℃annealing samples,Msdecreased from 44.59 to 21.73 emu/g,Mrdecreased from14.04 to 10.32 emu/g andHcincreased from350 to 720 Oe, respectively. Itwas obviously shown that the magnetic properties of samples change corresponded to the doping content of Cr3+. XRDmeasurement also showed thatthe crystallite size and cell parameterof samples decreased as the increasingof Cr3+doping content. These results affirmed that Cr3+entered the lattice ofNiFe2O4after being annealed at 600℃. The existence of Cr3+in the structure ofNiFe2O4dramatically raised the stabilityof the spinel structure and CO2cycle decomposition times. Pure NiFe2O4lost its activity just after 15 cycle reactions, and the phase abundance ofNiFe2O4remained about5%, while Cr3+doping NiFe2O4still had some activities after 50 reaction times and the phase abundance of NiFe2O4still had 20%.