The Research Of Physcial Property In Policrystalline Samples Eu(Fe_1-xNi_x)As₂

The first report of superconductivity in LaO1-xFxFeAs at 26K by the Hosono' s group in 2008 has attracted people to explore higher T?in iron-based superconductors.Until now,the research of iron-based super-conductors have made significant progress.However,the exploration in this area is still ongoing.Simultaneously,iron-based superconductors have provided abundant materials for our study of superconductivity.Recently,the successful synthesis of iron-based superconductor parent EuFeAs2 and the superconductivity of Eu1-xLaxFeAs2 have attracted our attention.We synthesize polycrystalline samples of Eu(Fe1-xNis)As2 which appears superconductivity by the solid state reaction method.Eu(Fe1-x Nix)As2 is helpful to study the relationship between magnetism and supe-rconductivity.In this paper,we mainly introduce the systematic study about physical properties of Eu(Fe1-xNi2)As2.This paper includes three chapters:The first chapter mainly reviews the origin of supercondu-ctivity,the development of iron-based superconductors and some theor-etical knowledge related to iron-based superconductors.The second chap-ter mainly introduces some basic measurement methods of iron-based superconductors,including structure(by XRD),magnetism(by SQUID),res-istance and specific heat(by PPMS).In the third chapter,firstly,we review the development of history about the new 112-type iron-based superconductors.Then we grow a series of polycrystalline samples of Eu(Fe1-xNix)As2(x=0-0.15)by the solid state reaction method.We use XRD to confirm the structure of Eu(Fe1-xNix)As2(x?0-O.15).By resistivity and specific heat measurements,we found that the parent compound EuFeAs2 shows distinct anomalies probably due to the Fe2+related anti ferromagnetic phase transition near 100K and the Eu2+related antiferromagnetic phase transition at 40K.By replacing Fe with Ni,the Fe2+ related anti ferromagnetic phase transition is quickly suppressed and then superconductivity appears.When the doping level x=0.04,the highest superconducting transition temperature reaches 18.2K which is higher than that of the La-doping at Eu site.By magnetic measurements,we found metamagnetic transition and ferromagnetism in parent compound EuFeAs2 and polycrytalline samples of Eu(Fe1-xNix)As2(x=0.03,0.04,0.05)which shows abundant magnetic properties.