Preparation Of Barium Hexaferrite Films Based On PLD

Hexagonal barium ferrite(BaFe₁₂O₁₉,Ba M)are widely used in permanent magnets,magnetic recording and microwave device because of its great properties including large uniaxial magnetocrystalline anisotropy field,high saturation magnetization,high coercivity and wonderful chemical stability,mechanical strength.With the development of microwave device towards miniaturization,integration and high frequency,traditional barium hexaferrite bulk are not applicative anymore,and it is a viable way by preparing barium hexaferrite into film forms.on the other hand,when barium hexaferrite film are used in microwave device,the thickness,crystallization,density,pore will affect the properties of device greatly.Therefore,it is meaningful for the miniaturization,integration and high frequency of microwave device by studying the preparing high-quality barium hexaferrite film.In this paper,we focus on preparing of high-quality barium hexaferrite film.In this paper,barium hexaferrite powders was prepared firstly,and the powders was sintered to be target which used for film deposition next.In order to preparing high quality barium hexaferrite film,powders with excellent properties should be prepared at first.Thus,the effect of calcining condition on microstructure and magnetic properties were studied in detail.It is revealed hard to preparing single phase barium hexaferrite powders when calcining temperature is lower than 850 ?,and when temperature is higher than 850 ?,the grain size increased and homogeneity gradually deteriorated with the increase of temperature and holding time.In the meantime,better magnetic properties of powders were observed on smaller size and more uniform of grains.On the base of this conclusion,barium hexaferrite powders with excellent microstructure and magnetic properties were obtained on the condition of lower temperature but long holding time?850 ?-10 h?.The dependence of film thickness with surface morphology and magnetic properties were studied next.Films with different thickness were prepared and characterized.With increasing of film thickness,orientation gradually decreased and microstructure become worse,and Fe2+ content was found increased.All of these changes lead to deteriorate of anisotropy,and saturation magnetization value decreased after the first increase from 263 emu/cm3 to 379 emu/cm3.As for coercivity,it decreased from 600 Oe to 1100 Oe and keep constant next.To improve the magnetic properties of barium hexaferrite films prepared by traditional method,layered deposition and rapid annealing were carried out.Experiments proved that films prepared by layered deposition show better orientation,and the destruction of microstructure for inner stress was suppressed.It gives better magnetic properties to films.saturation magnetization of 304 emu/cm3 is obviously bigger than film prepared by traditional way of 276 emu/cm3.The coercivity of film was improved by using rapid annealing.As we know,film with smaller grain size own higher coercivity.Rapid annealing limits the growth of grain in the short heat treatment process.Finally,films with coercivity of 2797 Oe was obtained on condition of 1000 ?-90 s.