Synthesis And Characteristics Of Fe_1.125Te Alloys

As a new member in superconductor family,11system of iron-based superconductor has attracted more and more attentions recently for its simplest crystal structure in all superconductor materials. After studying11system of iron-based superconductor, researchers intend to figure out the mechanism of the superconducting, which would beuseful to understand the superconductivity more profound. In the work of this thesis, Fe1.125Te alloyshave been synthesized and Fe1.125Te thin films have been fabricated. The structural and electronic/magnetic properties have been systematically investigated.Fe1.125Te alloys have been synthesized by solid state reaction methods. It crystallizes in Cu2Sb-type structure with lattice constants of α=3.8231A and c=6.2808A (space group:P/4nmm). The composition of the alloys is confirmed by Energy dispersive X-ray spectrometer (EDX). The effects of nitrogen annealing on Fe1.126Te lattice structure and physical properties have been studied. Samples are annealed at different temperatures and various pressures respectively. It is found that the lattice constants α andc increased after annealed at temperature400～600℃. When the temperature is above850℃, the size of the unit cell returns to the similar size of the original samples. The magnetic-thermal curves both show a magnetic transition at128K after annealing at600℃in N2atmosphere and vacuum. The step-like magnetic-thermal curves were observed after annealed at900℃, which is associated with two magnetic transitions. In vacuum, the transition temperatures are122K and128K, while in the nitrogen, they are122K and138K. The resistance-temperature curves indicate a semiconductor to metal transition around69K for N2atmosphere annealing at both550℃and900℃.Fe1.125Te thin films have been grown using magnetron sputtering method.The growing parameters of the Fe1.125Te films are stuied, especially for the deposition temperature. We process a series of experiments and finally confirm that500℃is the optimum deposition temperature. After the Fe1.125Te thin films have been deposited, the thin films are in situannealed in nitrogen atmosphere at600℃. However, no effect is observedafter annealing in nitrogen for Fe1.125Te thin films. There might be two possible reasons for the results. Firstly, the experiments are not performed systematacially because of the limitation of the conditions. Secondly, the low nitrogen annealing pressure takes little effect to the thin films. If the thin films are annealed in high pressure, there would be some new phenomena emerging.