Characteristics Of Phase Formation And Coercivity Mechanism Research Of SmCo_x/α-(Fe,Co) Nanocomposite Magnet

SmCo-based nanocomposite magnets are the best candidates for the application ofhigh temperature magnets since high Curie temperature and temperature stability. SmCophase transition has a lot of kinds, and crystal structure and magnetic properties ofdifferent phase is various., and the Sm2Co17hard magnetic phase which is used currentlyhas high Curie temperature and saturattion magnetization compared with SmCo5, and theonly shortage is low coercivity, so make it clear that the phase transition process andcoercivity mechanism of SmCo magnetic hard phase is of great significance to improvethe properties of SmCo high temperature nanocomposite magnets.In this paper, SmCoX/α-(Fe,Co) nanocomposte permanent magnet were preparedvia high energy ball milling. The phase transition process and coercivity mechanism isstudiedby employing differential scanning calorimetry(DSC),ultra high vaccum annealing furnacewith two rooms, X ray diffraction(XRD)and vibrating sample magnetometer(VSM)techniques.First, choosing the optimum ball milling parameters to prepare amorphous precursorsof SmCoX/α-(Fe,Co) nanocomposites, briquetting. Then, the phase transition processe ofnanocomposite was studied by DSC analysis technology combined with XRD analysis ofdifferent annealing treatment. The results are as follows: amorphous phase crystallize to1:5,1:5transform to1:7, amorphous phase crystallize to1:7of pure SmCo5. Adding Cocontent is good for precipitation of1:7, and when Co is abundant enough, amorphouscrystal maybe crystallize to1:7phase directly. And amorphous phase crystallize to1:5,amorphous phase crystallize to1:7,1:5transform to1:7of powder containing alloyingelements.In order to avoid the low density of bulk affects magnetic performance, we make thebulk high pressure processing at room temperature after annealing temperature is650℃of pure SmCo5、powder of adding Co and580℃of powder containing alloying elements,then research the coercivity mechanism、exchange coupling and magnetic performance.The results show that the coercivity is controlled by a domain-wall-pinning mechanism, and it is nonuniform domain-wall pinning. Exchange coupling effect are dominated bydipolar interactions. The saturation magnetization and remaneance have a certain degreeof increase and the coercivity hane no significant change after high pressure comparedwith high pressure before. The comparison of the three components of the magnetichysteresis loop confirm again the coercivity of pure SmCo5is the largest, and the pinningfield is the strongest, as well as, the coercivity of powder of adding Co is the least, and thepinning field is the weakest.