Controllable Electrodeposition Of FePt Thin And Nanowire Film From Ionic Liquid System

As a kind of perfect materials in ultra-high density magnetic recordingmedia system, FePt in a bulk state possesses a large uniaxial magnetiocrystallineanisotropy. According to its special feature, scholars and researchers pay muchattention to it. In the thesis, we mainly make full use of cyclic voltammetry andpulsed electrodeposition method, change composition of plating bath andelectrodeposition conditions to get FePt monolayer films, multilayer films andnanowires. The composition of ionic salts, solvents, chelating agents and theexperimental parameters of temperature, potential, current were optimized toimprove the surface performance. The main contents of this thesis were divided intothe following three parts:(1) Preparation and performance of FePt magnetic monolayerBy changing the bath composition and deposition potential, FePt monolayerpreparation conditions were optimized. The results showed that FePt film wereobtained in non-aqueous ionic liquids and the composition of Fe increased with theincrease of deposition potentials. The ferromagnetic FePt films were obtained whenthe atom ratios of Fe and Pt near1:1. By analyzing cyclic voltammetry, the reductionof Fe(II) to Fe in the ionic liquids is irreversible controlled by diffusion. When fixeddeposition potential, with the Fe (II) concentration increases, atom ratios of Feincrease. Film thickness increases from10nm to47nm, the coercivity increasesform350Oe to546Oe and then decreases to400Oe. When atomic ratio of Fe andPt is close to1:1, FePt film surface is smooth, dense grain and no pores.(2) Preparation and performance of FePt magnetic multilayerFour-layers and ten-layers FePt thin film were electrodeposited in ionic liquid.Chelate mechanism of EMIC, FeCl2, and (NH4)2PtCl6were analyzed by UV-visiblespectrophotometer. In the preparation of (Fe80Pt20/Fe50Pt50)2four-layer films, SEMmicrographs shows Fe80Pt20layer thickness is5μm (400s), Fe50Pt50layer thicknessis7~35μm (400s~2000s). The chronoamperometry indicated that reduction ofFe50Pt50on a Cu electrode corresponds to a three-dimensional instantaneous nucleation growth process with diffusion-controlled growth. With the increase ofdeposition time (15s~30s), the thickness of Fe50Pt50layer increased from118nmto300nm. With the increase of deposition time(10s~30s), the thickness of theFe2Pt98layer increased from75nm to294nm. Perpendicular coercivity valuesincreased from153Oe to800Oe when thickness of Fe50Pt50layers increased from118nm to300nm. Parallel coercivity values are not obviously changed when theFe50Pt50or Fe2Pt98layers thickness had been varied.(3) Preparation and performance of FePt nanowiresFePt nano-wire was electrodeposited on Si(111) substrate in non-queous liquids.Different range of deposition time are applied to prepared FePt nanowires, the layersatom ratio of iron are near to50at%. The diameter increased (95nm-155nm) whenthe deposition time increased from600s to1000s, coercivity values were increasedfrom234Oe to486Oe. The sharp peak labeled as (111) belonged to the fct FePt.