Coercive Force of γ-Phase in WC-Co Cemented Carbides

The influence of γ-phase composition in WC-Co cemented carbides on its specific coercive force H_(sc) hasbeen studied by analysing the imitative alloys of γ-phase. The results show that the H_(sc) of γ-phase is lower thanthat of pure cobalt, because the solute W can raise γ-phase H_(sc) but the carbon exhibits more intense negativeeffect on H_(sc). The effect is enhanced with raising the C solubilities in γ-phase.

Improvement of Coercive Force of(CoFe)_3O_4 by Doping Ce

Ce_x(CoFe)_(3-x)O_4 ferrites with different contents of Ce have been prepared by wetchemical method. The phases, morphologies and magnetic properties of the products were studied.It has been found that the products were a single phase with spinel structure and consisted of granular particles in most cases.The coercive force of the products increased with the increase of concentration of Ce￣(4+) in the reaction solution.On the other hand,if Ce￣(3+) and Ce(OH)_4 were present in the reaction solution,some rod-shape crystals in the products were observed, which causes a great increase in coercive force,and the optimum value was obtained when[Ce￣(3+)] was about 5% of the total([Ce￣(3+)]+[Ce￣(4+)]).

Study on Coercive Force of Metallic Cobalt Powder

The experimental regularity and the mechanism of coercive force of metallic cobalt powders and WC Co mixture powders used for WC Co cemented carbides production were explored. The results show that the specific coercive force H sc is a practical physical parameter which can show exactly the demagnetization characteristic of cobalt, and its magnitude is related to structure of cobalt. The H sc of WC Co mixture powders bears a simple positive going relation to Co content in them when the structure of cobalt is constant. It increases with fining and well distributing of cobalt particles in WC Co mixture powders due to the increase of the magnetic moment interaction of adjacent cobalt particles and the residual stress existing among powder particles by grinding.

Effect of Nd^(3+) substitution on structural and magnetic properties of Mg-Cd ferrites synthesized by microwave sintering technique

Nd3＋ substituted spinel ferrites with formula MgxCd1-xNd0.03Fe1.97O4（x = 0.0.2,0.4,0.6.0.8 and 1.0）were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were used as starting chemicals. The samples were sintered at optimized power of 70 W for10 min in a microwave oven（800 W）. The structural analysis of these samples was done by using X-ray diffraction, scanning electron microscope and Fourier transform IR techniques. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. The influence of Nd3＋substitution on various structural parameters of Mg-Cd ferrites was reported. IR study indicates the spectra contain two intense absorption bands around 600 and 400 cm^（-1） in addition with four extra bands. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer.The crystallite and grain size dependant magnetic properties are observed. The composition Mg_（0.6）Cd_（0.4）Nd_（0.03）Fe_（1.97）O_4 has better magnetic properties that can be used in recording media. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.

Magnetic Properties and Coercivity of MnGa Films Deposited on Different Substrates

MnGa films were grown by magnetron sputtering on thermally oxidized Si（Si/SiO2） and glass substrates. Films grown on single-crystal Si（100） substrate with different underlayers were prepared for comparison. It is found that the Si/SiO2 substrate is more suitable for growing high-coercivity MnGa films than the glass substrate, which is the result of the isolated-island-like growth. A coercivity of 9.7 kOe can be achieved for the 10 nm MnGa films grown on Si/SiO2 substrate at substrate temperature TS of 450 °C.Optimized experimental conditions are specified by changing the thickness of the MnGa films and the temperature of the substrates.