Influence of Ho substitution on structural, magnetic and microwave absorption properties of PbM-type hexaferrites nanoparticles

Ho substituted lead hexaferrites, PbCo0.5Sn0.5Ho (x) Fe11-x O-19 (x = 0.00-0.75) were successfully prepared by a citrate combustion process. Saturation magnetization and coercivity were measured from MH-loops taken on vibrating sample magnetometer. X-ray analysis reveals that in all samples M-type structure exist with few secondary phases. The results of X-ray diffraction analysis show that the particle size is inversely related to the dopant content. Microwave absorption properties of the nanocrystalline lead ferrite (PbCo0.5Sn0.5Ho (x) Fe11-x O-19) for single-layer investigated in a frequency range of 2-18 GHz. Results indicated that the substituted Ho can greatly improve the microwave absorption properties of PbCo0.5Sn0.5Fe11O19 hexaferrites. For sample with x = 0.75, a minimum reflection loss of -33 dB was obtained at 16.5 GHz for a layer of 1.8 mm in thickness. The microwave absorption performance of PbCo0.5Sn0.5Ho0.5Fe10.5O19 ferrite gets significant improvement: The bandwidth below -15 dB expands from 12 to 16.5 GHz, and the peak value of reflection loss decreases from -18 to -37 dB. The minimum reflection loss reaches -34.2 dB when the substitution amount of the Ho3+ ions is 0.25. Also results show that the peak positions of the minimum reflection loss shift toward higher frequency band.