Study Of Magnetic Property And Cation Distributions In Boron-doped MFe₂O₄?M=Ni,Mn? Spinel Ferrites

Spinel ferrites are a magnetic material with wide applications.There are eight formula units in each?A?[B]₂O₄ spinel ferrites unit cell.The larger oxygen anions form a close-packed face-centered-cubic structure with the smaller metal cations occupying interstitial sites:the tetrahedral?8a?or?A?sites and the octahesral?16d?or[B]sites.There are lots of studies about non magnetic cation doping spinel ferrites.But there are a few of studies about B ions doping spinel ferrites.In this work,the spinel ferrites B_x1Ni_x2Fe_3-x1-x2O₄?0.000?x₁?0.333?and B_x1Mn_x2Fe_3-x1-x2O₄?0.000?x₁?0.176?were prepared by using the solid state reaction technique.We measured two X-ray photoelectron spectra?XPS?of Ni-series of samples.We measured the X-ray diffraction?XRD?spectra of the two series of samples at room temperature and the hysteresis loops of two series of samples at 10K and 300K.We therefore analyzed the crystal structure,magnetic property and the cation distributions of the two series of samples.?1?By analyzed XPS,we found that most of boron cations were lost in our preparation process of boron doped spinel ferrite samples B_xNi_1-xFe₂O₄ and B_x Mn_1-xFe₂O₄.We therefore obtained the ferrite samples B_x1Ni_x2Fe_3-x1-x2O₄ and B_x1Mn_x2Fe_3-x1-x2O₄.?2?By analyzed XRD patterns,we found that all the samples have the single-phase spinel structure with space group Fd3m.As boron doping level x₁ increasing,the lattice parameter a of BNi series samples increases,while the a of BMn series samples decreases.?3?The magnetic measurement results at 10 K indicate that the average molecule magnetic moment,?_obs,increases with increasing B content x₁ for BNi series samples,while?_obs decreases with increasing B content x₁ for BMn series samples when x₁>0.026.?4?The cation distributions in the samples were obtained by fitted the curves of?_obsbs versus x₁ using the O2p itinerant electron model and the quantum mechanical potential barrier model.For the BNi series samples,the cation content ratio of B²⁺ions entered[B]sites to B doped level x₁ is more than 85%;the content ratio of B(B²⁺+B³⁺)cations entered[B]sites to x₁ is more than 92%.For BMn series samples,both B²⁺contents at the?A?sites and at[B]sites increase with increasing x₁,but the B²⁺content at the[B]sites is more than that at the?A?sites;the ratio of B²⁺content sum at the?A?sites and[B]sites to doped level x₁ is more than92%.In the two series samples,the distributions of Mn and Ni cations have the similar characteristics.