Research On The Magnetic Properties Of Layered Structure Van Der Waals Crystal CrBr₃

Two-dimensional layered materials have wide application prospects in the fields of electronic information engineering,energy utilization,biomedicine and other fields due to their rich and excellent physical and chemical properties.Since graphene was proved to be a stable two-dimensional layered material in 2004,a large number of van der Waals(vdW)materials with a layered structure have begun to be paid attention by scholars,and become the focus of current scientific research.The vdW material with a layered structure can be cleaved by physical and chemical methods to form a single layer of two-dimensional material with an atomic thickness,which exhibit unique physical characteristics that are different from conventional bulk materials.These novel physical characteristics will open a new era of information materials and devices in the future.Most of the existing two-dimensional materials are semiconductors.The lack of magnetic two-dimensional single-layer materials hinders the development and application of new magnetic,magnetoelectric,and magneto-optical materials and devices.There are many types of magnetic vdW materials with a layered structure,but after these materials are cleaved into a single layer,the magnetic disappears.So researchers are still looking for bulk materials that can maintain magnetic properties when thinning down to monolayer.Until 2017,researchers first confirmed through experiments that the single layer CrI3 and CrGeTe3 retained intrinsic ferromagnetism,setting off a wave of research on two-dimensional magnetic materials.CrBr3 is a vdW magnetic material with a layered structure.It has the same structure as CrI3 and is a potential two-dimensional magnetic material.Until now its single crystal is not easy to obtain,and research on its magnetic properties are few.In this paper,CrBr3 single crystal was synthesized by chemical vapor transport method.The results of structural measurement showed that CrBr3 had a rhombic BiI3 structure and its layers were combined by vdW force.The magnetic transport measurement specifically analyzes the magnetic state and magnetic transition of CrBr3,which shows that CrBr3 is a typical ferromagnetic material with a Curie temperature Tc of about 33 K.In addition,we use the method of scaling theory to analyze the critical behavior of CrBr3 during the magnetic phase transition,and we get ?=0.258 and ?=1.237,which do not belong to the traditional critical interaction model.The analysis results of CrBr3 magnetic entropy change show that its paramagnetic-ferromagnetic transition at Curie Temperature Tc is a second-order phase change,and the maximum magnetic entropy change is about 7.2 J·kg-1·K-1 when the magnetic field change is 5 T.The maximum value of the relative cooling efficiency reaches about 191.5 J·kg-1.CrBr3 has the advantages of high refrigeration efficiency,environmental friendliness,low cost,etc.