| Recently, 3d transition-metal nitrides ANM3 (A= Cu,Ag, Ga, Sn, Al, Zn, Ge, I,etc. M= Ni, Mn, Fe,V,Cr, C, etc.) have become a hotspot in the field of new materials owing to their abundant physical properties and potential functionalities.In this dissertation, chromium-based and cobalt-based nitrides ANM3(M=Cr, Co)are selected to study the experimental preparation, crystal structure, the magnetic property, the electrical transport, the thermal transport, and their correlation effects.On this basis, by systemic chemical doping on parent compounds, we attempt to conclude the effects and evolution of element doping on the physical properties, to optimize the functional parameters, thus to provide important references for the material designs of this system. The main contents are included as follows:1. Chromium ternary nitrides ANCr3 are usually synthesized by the solid state reaction of A and the precursor NCr. We successfully prepared different crystalline-sized NCr by both coprecipitation and the solid-gas reaction method, we present the experiment condition and process in detail in this dissertation.2. We have systematically studied the synthesis, crystal structure,electrical transport,capacity and thermal transport of polycrystalline PNCr3. The results indicate that PNCr3 is a quasi-two-dimensional structure, and it shows good metallic behavior, at the same time, the Fermi-liquid behavior is observed at low temperatures. The fitting results of low-temperature resistivity and specific heat suggest a considerably strong electron-electron correlation for all our sample. And the strong electronic correlation may account for the absence of superconductivity down to 2 K. Moreover, the total thermal conductivity is attributed to the combined action of electrical thermal conductivity and lattice thermal conductivity.3. The crystal structure and basic physical properties are detailedly studied for the Cr-based parent compound GeNCr3 and its chemical doping compounds. As a result, GeNCr3 adopts the tetragonal-antiperovskite structure, and a structure phase transition at 420 K has been confirmed, which is the driving force of the first-order antiferromagnetic (AFM)-paramagnetic (PM) phase transition. Moreover, the specific heat Cp(T), the resistivity ?(T), and calorimetric measurements all have abnormality around structural transition temperature, indicating a strong coupling between electron, phonon and the spin. The results of Mn or Fe doping at Cr site suggest that the transition temperature decreases with the increase of the Mn/Fe content. We proposed that the doping causes a gradual change of octahedron shape in the tetragonal structure. Besides, the results of Si doping at Ge site suggest that the transition temperature does not continue decreasing as the Si content increses. It is due to the the effect on the NCrb octahedron by doping at Ge site is too tiny.4. We synthesized single-phase Co-based nitride GeNCo3 by a solid-gas reaction successfully,and studied its crystal structure,magnetism,electrical and thermal properties in detail. The magnetic measurement suggests that a canonical spin-glass (SG) behavior is observed in GeNCo3, and the relevant parameters:freezing temperature T0=79.43 K, dynamical exponent zv= 6.156, and flipping time?0= 5.0 × 10-12 s. The origin of the SG state in GeNCo3 is likely due to the atomic disorder introduced by the Ge vacancies. The specific heat at low temperatures,electrical and thermal transport properties are intensively investigated. Besides, we also synthesized ANCo3(A=Zn, In, Cd, Sn) successfully and studied their physical properties systematically. |
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