Investigation Of Preparation Method And Physical Properties Of RCrO₃ （R=Ho,Sm） Thin Film Of Rare Earth Chromite

In recent years,extensive research has been carried out on the ferriticity of orthogonally distorted perovskite rare earth chromite,such as HoCrO₃ and SmCrO₃.At present,most researches on RCrO₃are powder or block samples prepared by high-temperature solid-phase method.The physical properties of RCrO₃ are controlled by doping.In addition,there are also controls such as the control of annealing temperature and the morphology of samples.In this paper,we take RCrO₃（R=Ho,Sm）as the research object,and prepare thin film samples of different thicknesses by sol-gel spin coating.Effects on the structure,Raman mode and magnetic properties of RCrO₃（R=Ho,Sm）thin film samples.In the exploration of the preparation of HoCrO₃ films with different thicknesses,we systematically explored the effects of sol solvents and sol concentrations on the annealing temperature of film samples on the preparation of HoCrO₃ films by sol-gel spin coating.Due to the hydrophobic nature of the substrate and its own intra-lattice stress,we need to pre-anneal the substrate at high temperature to remove its intra-lattice stress before spin coating the sample.Through the characterization of XRD diffraction patterns under different conditions,the optimal film preparation conditions were gradually obtained,that is,the precursor solvent was acetic acid,the concentration was 0.25 mol/L,and the film annealing temperature was 800°C for 2h.In order to further confirm the optimality of the film sample preparation conditions discovered by XRD test,the surface morphology of the film samples was characterized under different conditions,and the results further confirmed the optimal conditions for the preparation of HoCrO₃ films.With regard to the study of the properties of RCrO₃（R=Ho,Sm）thin film samples prepared by the sol-gel spin coating method,XRD tests showed that the thickness of the thin film samples of each thickness was good,no heterogeneous phase appeared,and belonged to the orthogonal distortion structure.Due to the lattice mismatch between the substrate and the sample,the Raman phonon mode of the sample increases with the thickness of the film,and the A_g（6）,B_3g（3）,and B_2g（3）phonon modes will slightly increase to the high wave number.Moving,through the SEM test of the cross section of the sample,it was obtained that all films of different thicknesses were well crystallized without large pores and cracks.In the HoCrO₃ sample,the sample temperature-dependent magnetization curve shows that as the film thickness increases,the magnetization increases,and the Neel temperature moves slightly to high temperature.Due to the Dzyaloshinskii-Moriya（DM）interaction of twisted Cr-O-Crbonds,the phenomenon of negative magnetization is shown in ZFC mode.In the SmCrO₃thin film samples,from the temperature-dependent magnetization curve,it can be found that the Neel temperature is around 190K,which is less than the previous block and powder article reported 194K.With the increase of film thickness,due to the coexistence of ferromagnetism and antiferromagnetism in the film sample,the sample gradually showed negative magnetization.Through the XPS characterization of the sample to obtain the electronic structure information of the sample.X-ray photoelectron spectroscopy shows that Cris in the trivalent.When HoCrO₃ films get thin,the hybridization of Ho 4f with O 2p orbital is strengthened,while the hybridization of O 2p and Cr3d is more prominent in SmCrO₃.