Research On Magnetic And(magnetic)dielectric Properties In RCrO₃(R=Ce,Pr,Tb,Tm,Lu) System

Perovskite-type compounds have attracted extensive research interests in recent years due to their novel physical properties and applications in sensors,catalysts,data storage,and magnetoelectric couplers.In this paper,the crystal structure,magnetic properties and(magnetic)dielectric properties of the system are analyzed in detail the rare earth chromium oxide RCr O₃(R=Ce,Pr,Tb,Tm,Lu).The primary research contents and conclusions are as follows:The Tm Cr O₃ and Lu Cr O₃ samples were prepared by the traditional solid-phase method,Pr Cr O₃ and Tb Cr O₃ samples were prepared by the sol-gel method,and the Ce Cr O₃ samples were prepared by the combustion synthesis process.The XRD pattern of the sample is consistent with the characteristic peak of the standard PDF card.The EDS data shows that there are no impurities in the sample,and R:Cr:O?1:1:3.The results indicate that the prepared sample is single-phase polycrystalline.For the M-T(magnetization vs temperature)curve,the high temperature section follows the Curie-Weiss law.The Neel temperature(T_N)increases with the increase of the rare earth ion radius,indicating that T_N is not related to whether R³⁺is magnetism or not.It is may related to the lattice distortion of the system.In field-cooled mode,the magnetization reversal phenomena of Ce Cr O₃ and Tm Cr O₃ are due to the competitive interaction between Cr and Ce/Tm magnetic sublattices.The spin reorientation of the sample at low temperature is related to the transition of the magnetic structure.For the?'-T(dielectric constant vs temperature)curve,the system shows the characteristics of dielectric dispersion and giant dielectric constant.For the tan?-T(dielectric loss vs temperature)curve,the shift of the dielectric loss peak with frequency indicates that the sample has thermal activation relaxation.The dielectric relaxation at lower temperature is caused by oxygen vacancies in the sample,and the dielectric relaxation at higher temperature is derived from Maxwell-Wagner relaxation.For the?_AC-f(AC conductivity vs frequency)curve,the AC conductivity decreases with increasing temperature,indicating the semiconductor properties of the sample.According to the fitted s parameter value,the conduction mechanism model of RCr O₃is judged to be related barrier jumping and non-overlapping small polaron tunneling.The complex impedance spectroscopy shows that the dielectric relaxation of the sample is caused by the joint effect of the grain boundary and the grain relaxation.For the R_gb-T(grain boundary resistance vs temperature)curve,the grain boundary resistance of the sample is related to the mobility and concentration of carriers.For Ce Cr O₃ and Tm Cr O₃,the?'-T(dielectric constant vs temperature)curve at low temperature shows a dielectric abnormal peak,which does not move with the frequency.This is due to the ferroelectric polarization of the sample.The results of the AC susceptibility and the?'-T(dielectric constant vs temperature)curve at 2 T magnetic field show that the abnormal dielectric peak is due to the ferroelectric polarization induced by the magnetic order.