Chemical Solid-phase Synthesis Of L1₀-FePt Nanoparticles And Effect Of High Magnetic Treatment Under Field On FePt Nanoparticles

L10-FePt nanomaterials have wide application prospects,such as perpendicular magnetic recording,high performance permanent magnet materials,electrochemical catalysis and biomedicine because of its high magnetocrystalline anisotropy,good chemical catalytic performance and biocompatibility.However,the as synthesized FePt nanoparticles chemically disordered fcc structures.The nanoparticles with fccstructure should be converted into the L10(fct)structure by usingordered heating treatment.However,the ordered heating treatment usually leads to spheroidization,agglomeration and abnormal growth of nanoparticles,which seriously deteriorate performances and application of the particles.In this work,chemical solid-phase reaction processhas been employed to solve this problem.Precursors and salt were fully mixed.During the reaction process,the nanoparticles were isolated to prevent their abnormal growth and agglomeration by salt powders.L10-FePt nanoparticles with fine and uniform size could be obtained by thisone-step synthesis.This work also introduced high magnetic field heating treatment to prepare L10-FePt nanoparticles.The relation between high magnetic field on the ordering and magnetic properties of FePt nanoparticles has been investigated.It's expected to find new way for preparation of ordering FePt nanomaterials.The main research results are shown as follows:In chemical solid-state method,the properties and structure of the nanoparticlesare related to reactive process.With increase of reactive temperature,the ordering degree of the nanoparticles gradually increases.The coercivity of the particles increases with the increase of the temperature.The reacting time has influence on the ordering degree and the magnetic properties of the particles.However,excessive reactive time will lead to the particles with large size and because of abnormal growth.The mixing ratio of the precursors and salts also has an important effect on the synthesized FePt particles.With increasing the mixing ratio,the coercivity of the particles and ordering degree increased.Coercivity of the particles reached the maximum value when the mixing ratio was 1:100,and the mixture ratio continually increased,and the magnetic properties decreased.In this experiment,L10-FePt nanoparticles with good magnetic properties and uniform size were obtained at 700? for 60 min,under mixing ratio of 1:100.Coercively of the synthesized particles reaches 2.4 T,the saturation magnetization Ms is 47 emu/g,the remanent magnetization Mr is 30 emu/g,and the maximum energy product(BH)max is 145.2 kJ/m3.The FePt nanoparticles synthesized by wet chemical method have been heated under high magnetic field.The structure of the nanoparticles heated without magnetic was L12-Fe3Pt.With increasing magnetic field,L10 structure of nanoparticles began to appear.When the magnetic field was 12 T,L10-FePt nanoparticles could be obviously found according to analysis of XRD pattern.The FePt nanoparticles synthesized by low temperature chemical solid state method have also been heated under high magnetic field.It was found that the high magnetic field heat treatment can greatly improve the ordering and magnetic properties of FePt nanoparticles.The ordering degree of the FePt nanoparticles could be tuned by changing magnetic field.In addition,with the increase of magnetic field,the size of nanoparticles decreases.These evidences indicate that the high magnetic field can effectively promote the degree of FePt,and reduce the ordering transformation temperature of L10-FePt.The order of the FePt nanomaterials can be controlled by tuning the intensity of the magnetic field.Therefore,the heating treatment under high magnetic field might be a new path to prepare FePt materials with controllable ordering degree.