Synthesis And Properties Of 1111-type Cr-based Compound CeCrAsO

The discovery of iron-based superconductors has led to a renewed interest in ZrCuSiAs-type?also known as 1111-type?transition metal compounds.On the one hand,it is expected to find new superconductors by element substitutions.On the other hand,the novel physical properties related to these compounds have also attracted intensive research interest.Among such compounds containing rare earth ions,the introduced 4f electrons from some rare earth ions can be coupled to the conduction electrons,and the coupling strength can be modulated to induce interesting physics such as quantum phase transitions.Kondo effects and unusual magnetic properties have been found in many CeT P nO?T=transition metal,P n=P,As?systems and similar compounds.In this thesis,the 1111-type structural compound CeCrAsO was synthesized,and its properties were studied by systematic measurements.The following innovative results were obtained.We successfully synthesized the ZrCuSiAs-type oxyphosphor compound CeCrAsO and car-ried out transport,magnetic and heat capacity measurements.We found that,unlike the LaCrAsO system,CeCrAsO may be issued two phase transitions at T_SR=38 K,namely a first-order phase transition caused by the spin reorientation of Cr²⁺ions and the AFM phase transition caused by the magnetic moment of Ce³⁺ions.The system has a crystal field effect?CEF?of Ce ions at lower temperatures.At room temperature,the Cr²⁺ions have long-range magnetic order.At the same time,the splitting of its ground-state doublet of Ce³⁺ions,was induced by the internal crystal field?the energy level difference was 3.93 meV?.The nature of CeCrAsO reflects the interaction between Cr-3d and Ce-4f electrons,which helps to further understand the intrinsic physics of such compounds.This thesis is divided into three chapters.The first chapter is the introduction,which mainly describes the research background of CeCrAsO compounds and the crystal field effect?CEF?.The second chapter is on the experimental methods,including the preparation method of polycrystalline sample,and methods of physical property measurements.The third chapter introduces our work,namely the synthesis,structural characterization,and physical properties of the 1111-type Ce-based compound CeCrAsO.