Study On The Properties Of Ru-doped La₂NiMnO₆ And Zn-Ir Co-doped SrFe₁₂O₁₉

Nowadays,electromagnetic interference pollution has become more and more serious with the rapid development of the electronic and electric equipment.Highly effective microwave absorbing materials are in urgent need.Ferrite as a microwave absorbing material has attracted the attention of many scholars.In response to this topic,the effect of Ru ion doping on the double perovskite-type oxide La₂NiMn O₆ and Zn-Ir co-doping on hexagonal ferrite SrFe₁₂O₁₉ were studied.The results of structure,magnetic properties and microwave absorbing properties are as follows:The La₂NiMn_1-xRu_xO₆ compounds were synthesized by solid state reaction.The cations’orderings of La₂NiMn_1-xRu_xO₆are improved with the Ru doping especially in x≥0.5 when researching its structure.The magnetic properties show that the x=1.0sample is antiferromagnetic with the Neel temperature at 23 K.The antiferromagnetic transition is also observed in the other samples with the transition temperature slightly varying from 23 K to 38 K.In x=0.1,one ferromagnetic transition is observed at 242K,and it linearly decreases to 38 K in x=0.8.The magnetic moments are calculated based on the superexchange model.From the comparison of the calculated and the measured one,it suggests that both ordered and disordered patches coexist in x=0.1and 0.3,while in x≥0.5 the cations are fully ordered.The Ru doping increases the dielectric permittivity due to the enhanced dipolar polarization.In x≥0.8,the effective absorption with RL<-10 d B is able to cover the full frequency range of 2.2 GHz–18GHz.SrFe_12-2xZn_xIr_xO₁₉ were synthesized by solid state reaction.All the SrFe_12-2xZn_xIr_xO₁₉ are single phased and crystallize in the hexagonal ferrite with the space group as P6₃/mmc.The saturation magnetization linearly decreases with x.It is consistent with the diluting effect of the nonmagnetic Zn and Ir doping.The coercivity rapidly decreases with the Zn and Ir doping.Zn and Ir co-doped decreases the anisotropic field greatly.Both the permeabilities and the permittivities increase with the increasing Zn and Ir doping as x≤0.5,and decrease in x=0.7.The different behavior is due to the impurity in x=0.7.The high permittivity in x=0.5 are due to the leakage conduction as deduced from the Cole-Cole semicircles.Debye relaxations take function in x=0.1,0.3 and also 0.7.The impedance matching and the attenuation factor have the best values in x=0.5.As a result,the x=0.5 sample has a very good microwave absorbing property with the single-layer bandwidth（RL<-10 d B）as broad as 12.1 GHz at the thickness of 2.1 mm.If the thickness varies from 1.3 mm to 9.5 mm,the bandwidth with RL<-10 d B covers the full frequency range of 1.5-18 GHz.In result,SrFe₁₁Zn_0.5Ir_0.5O₁₉ has better performance than the other M-type ferrites and most of the advanced materials reported.