Study On Multi-Ferroic Properties Of Two-Dimensional Layered Material CuMP₂S₆?M=Cr,V?

So far,a lot of achievements have been made in the study of multiferroic materials,but there are still some problems: the first kind of multiferroic materials have weak magnetoelectric coupling effect;the second kind of multiferroic materials have low ferroelectric polarization and Curie temperature;the three-dimensional multiferroic materials lose ferroelectricity and magnetism when they fall to the two-dimensional scale,etc.These problems limit the practical application of multiferroic materials,but also guide the researchers to carry out continuous exploration.Since the discovery of graphene,two-dimensional van der Waals materials have made great progress.Two-dimensional magnetism,two-dimensional ferroelectricity and two-dimensional multiferrous have been reported in endlessly.There are many forms of multiferrousness in two-dimensional materials,including class I multiferrousness,class II multiferrousness and magnetoelectric coupling forms outside of them.The research on two-dimensional multiferrousness is also expected to solve some bottleneck problems in the research of traditional single-phase multiferrousness materials.Although a large number of researchers have predicted many two-dimensional multiferroic materials and the existing forms of magneti sm,ferroelectricity and magnetoelectric coupling through the first principle calculation and other methods,due to the factors such as difficult synthesis of materials,material and its instability,the experimental research and verification of these materials are relatively few.The transition metal thiophosphite is a kind of van der Waals crystal,which is similar to the transition metal sulfide.The force between layers is weak.It can easily obtain a few layers or even a single layer of samples from a large single crystal by mechanical stripping.The transition metal thiophosphite CuMP₂S₆?M=Cr,V?represents one of the two-dimensional multiferrous materials that have been found at present.The high-quality single crystal of CuMP₂S₆?M=Cr,V?was prepared by chemical vapor transport method.A series of experimental studies on CuMP₂S₆?M=Cr,V?were carried out to verify the existence of multiferrous in the bulk samples of CuMP₂S₆?M=Cr,V?.The research contents are as follows:?1?The large-scale and high-quality single crystal of CuMP₂S₆?M=Cr,V?was prepared by chemical vapor transport method.The X-ray diffraction and energy scattering X-ray spectrum of the single crystal were measured.The quality of the single crystal was further confirmed,which laid the f oundation for the subsequent characterization of physical properties.?2?Through the measurement of the magnetic susceptibility and the analysis of the magnetic susceptibility curve and the measurement of specific heat,it is confirmed that the antiferromagnetic phase transition temperature of CuCrP₂S₆ is TN1=32 K,and the Curie temperature of CuVP₂S₆ is TC=20 K.?3?Through the measurement and analysis of the dielectric constant,specific heat,temperature dependent Raman and hysteresis loop of single cry stal samples,CuVP₂S₆ and CuCrP₂S₆ are ferroelectrics at room temperature,CuCrP₂S₆ has structural phase transition at 173 K,and it is antiferroelectrics below 155 K.The ferroelectric transition Curie temperature of CuVP₂S₆ is above room temperature.?4?Through further analysis of the data of magnetic susceptibility and dielectric constant,it is found that the magnetoelectric coupling between CuMP₂S₆?M = Cr,V?is weak,which conforms to the theoretical prediction that this kind of system material is the first type of multiferroic material.