Synthesis And Physical Characterization Of Re₂CuRu/IrO₆(Re=Nd,Sm,Gd)

Ferromagnetic insulators have become the main carrier for spin devices to transmit information due to their ability to use magnetons to transfer spin information and reduce device power consumption.Among them,the ideal ferromagnetic insulator material for spin devices is undoped perovskite material.Double perovskite materials have become one of the ideal candidates for ferromagnetic insulators due to their special properties such as high Curie temperature,semi-metallicity and metal-insulator transition.However,the current physical property control of double perovskite materials mainly focuses on element replacement at the B position,and the research on physical property control by element replacement at the A position is rarely reported.Therefore,the thesis replaces the La ions in the double perovskite La₂Cu Ru O₆ with the lanthanide elements Nd,Sm and Gd ions with smaller ionic radius at the A site,and studies the regulation effect of the substitution of the A site elements on the physical properties of the system.In the thesis,the double perovskite compound Re₂Cu Ru O₆(Re=Nd,Sm)was synthesized by solid-phase reaction method,and the structure and magnetic properties of the compound were studied.Through comprehensive analysis of X-ray diffraction(XRD)and first-principles calculation(DFT)phonon spectra,it is found that the sample is a monoclinic crystal system with a structure phase of P2₁/n in the space group.The analysis of structure shows La³⁺is replaced by the smaller rare-earth ions Nd³⁺and Sm³⁺,forming in monoclinic P2₁/n structure,which results in the decrease of Cu-O-Ru bond angles and the simultaneous enhancement of magnetic interactions,lead to higher transition temperature than that of La₂Cu Ru O₆.At the same time,the analysis of the magnetization curve found that Nd₂Cu Ru O₆ has ferromagnetism,and Sm₂Cu Ru O₆ may be a kind of ferrimagnet due to the existence of residual ferromagnetic moment.The consistent trends of the antisite defects and the upturn rate of the magnetic curves indicate that the antisite defects may play an important role on the magnetization at low temperature.In addition,this article tried to synthesize the Gd₂Cu Ru/Ir O₆ sample by the same preparation method and analyzed the X-ray diffraction pattern of the sample.It was found that the replacement of Ir ion would change the peak intensity and the position of the peak,while the replacement of Gd ion would increase the difficulty of synthesizing samples,resulting in the two samples not forming a single structure phase.