Direct Synthesis And Magnetic Performance Of L1₀-FePt Nanoparticles Prepared By Wet Chemical Method

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 FePt nanoparticles synthesized by normal method usually are chemically disorded fcc structure.In order to get high magntic performance,the nanoparticles with fcc structure should be converted into the Ll0(fct)structure by using ordered heating treatment.However,the ordered heating treatment usually leads to spheroidization,agglomeration and abnormal growth of nano particles,which seriously deteriorate performances and application of the particles.Although researchers have developed direct preparation technique,there are still disadvantage existing in available technologies that include loworcder degree of synthetic nanoparticles and using toxic high boiling solvents in the experimental process.Aiming at these problems,nontoxic ODE was used as the high boiling solvent,and L1₀-FePt nanoparticles were directly synthesized by adding third metal elements(Ag?Cu).In order to increase ordering degree of the FePt particles,a high magnetic field,which can facilitate ordering trainsition,was employed in this work.It's expected that FePt nanoparticles with good magnetic proeperties could be prepared by combination of high magnetic field and wet chemical method,which proposed a new pathto directly synthesize L1₀-FePt nanoparticles.The mechanism of FePt nanoparticle order transition would be discussed.This work will provide experimental and theoretical basis for the practicality of FePt nanoparticles.Firstly,FePt nanoparticles were synthesized by adding Ag and Cu elements.The relationship among synthesis process,particle properties and structure was studied.The coercivity of particles and ordering degree increases with the rising of synthesis temperature.The influence of additive metal element in the precursor on the ordering degree and magnetic properties of the particles was revealed.The ordering degree and magnetic properties of the particles increase with increasing the metal content.However,the order degree and coercivity decreased when the element was added excessively.The FePt nanoparticles synthesized by adding Cu element have better magnetic properties than that of the particlces synthesized by adding Ag element.The optimum process of preparation in this study is as follows:addition of Cu(Ac)2 as precursor,reaction for 3 hours at 360?.The FePt nanoparticles coercivity achieved to 2500 Oe.In addition,we have been prepared the FePt nanoparticles in high magnetic field.The results show that the FePt nanoparticles with Ll0 structure can be obtained at lower synthetic temperature.With the increase of magnetic field intensity,the ordering degree of nanoparticles becomes better,which indicate that high magnetic field can effectively promote the order transition of FePt and reduce the ordered transition temperature of L1₀-FePt.In this study,L1₀-FePtCu nanoparticles were obtained at 320? in high magnetic field This is the lowest temperature that has been reported at present.Therefore,the combination of wet chemistry method and high magnetic field may be a new direction for the direct synthesis of L1₀-FePt nanoparticles.