Structure And Electromagnetic Transport Properties Of R-T-M1:2:2and The Exploratory Study Of R-Ga1:3Intermetallic Compound Phase Rule

The magnetic and semiconductor materials are playing important role in current high information technology (IT) society. By designing combination of the characteristics for the two materials, one kind of novel IT material so-called magnetic semiconductor material was firstly reported in1988. We studied one kind of compound with rare earth, transition metal and Ge or Ga. Transition metal is being as magnetic elements, and rare earth metal is used to modulate the magnetic ordering and anisotropy by the4f-3d interaction.Based on the previous studies for the RT2M2(R:Rare earths; T:transition metals; M:Si or Ge) intermetallic compounds, NdNi2Ge2, NdCo2Ge2, LaNi2Ge2and LaCo2Ge2are selected as the objections of this study. The sample was prepared by are-melting under a protective ultra-pure argon gas. The X-ray diffraction peaks were indexed by Trying method-TREOR and a least square method-PIRUM program. Rietveld structure refinement technology was used to determine the structures of RT2M2. The refined results show that RT2M2. crystallize tetragonal ThCr2Si2-type structure with a space group of I4/mmm, and Z=2. The lattice parameters of NdNi2Ge.2, NdCo2Ge2, LaNi2Ge2and LaCo2Ge2are a=4.120(1)A, c=9.835(0)A; a=4.039(8)A, c=10.151(1)A; a=4.189(2)A, c=9.907(2)A; a=4.105(6)A, c=10.264(7)A, respectively. The atomic occupations are the2a(0,0,0) position for the rare earth elements (Nd or La), the4d(0,1/2,1/4) position for transition metals (Ni or Co) and4e(0,0, z) position for Ge, respectively. Magnetic and electric properties were measured using superconducting quantum interference device magnetometer and a standard four-probe technology. Magnetic measurements indicate that NdNi2Ge2is paramagnetic, NdCo2Ge2is antiferromagnetic with a magnetic transition at room temperature. LaNi2Ge2and LaCo2Ge2are ferromagnetic with Curie temperature more than room temperature. Electric measurement implied that RT2M2are semimetal.Our studies reveal that Nd-Ga-M(M=metal element such as Ni, Cu) intermetallic compounds have excellent electronic transport property induced by doping magnetic element and have the potential application as a novel magnetic semiconductor compound, therefore, the research interest has been focused on this study. In this thesis, we are reporting the synthesis technology, phase structural analysis of the pseudo binary Nd-Ga alloy. NdGa3-xMnx and NdGa3-xTix (x=0.1,0.3,0.5and0.7) compounds. X-ray diffraction is employed to check the phases in these alloys, and the diffraction peaks are indexed with TREOR and PIRUM program. The crystal structure, unit cell volume and lattice parameters of NdGa3.xMnx and NdGa3-xTix (x=0.1,0.3,0.5and0.7) have been determined for all samples.Finally the issues and challenges in this study are discussed.