Silver powders were produced at rate of 2 kg/min by water atomization with the pressure of 80 MPa. SEM observation showed that the silver particles had various types of morphologies such as spherical, irregular and coarse. The volume average particle size and standard deviation determined by particle size analyzer was 8.2 μm and 4.15 μm, respectively. XRD revealed that as-prepared powders crystallized to silver with high crystallinity. TMA revealed that the shrinkage of as-prepared silver powders was about 25% after classified to 2.5 μm and then comparable with those obtained by chemical reduction method. The specific resistivity of silver paste obtained by silver powders derived from water atomization was superior to that obtained by silver powders derived from chemical reduction method.

We have developed Sm₂Co₁₇ sintered magnets whose Fe concentration is much higher than conventional Sm₂Co₁₇ sintered magnets. The pre-aging treatment leads to fine cell structure and improvement in squareness of demagnetization curves. As a result the (BH)_max of pre-aged magnets shows higher than that of no-pre-aged magnet. The inter-mediate heat treatment (IHT) induces the grain growth. We found that squareness of demagnetization curve has clearly improved by the IHT at adequate temperature. These results indicate that reducing the fraction of grain boundaries by increasing the grain size affects the behavior of domain-wall motion. Sm₂Co₁₇ sintered magnets fabricated adopting pre-aging treatment and IHT show (BH)_max of 282 kJ/m³.

To decrease the irreversible demagnetization of anisotropic ferrite magnets at elevated temperatures, it is required to outstandingly improve the squareness ratio (H_k/H_cJ), where H_k and H_cJ are the knee field and coercivity, respectively. The effect of ratio of anisotropy constant (K_u2/K_u1) on H_k/H_cJ for Sr_1-xLa_xFe_12-xCo_xO₁₉ (x = 0–0.4) sintered magnets was studied, where K_u2, K_u1, and x are the quartic and quadratic anisotropic constants, and the substituted amount, respectively. The accurate values of anisotropy constants were obtained from a Fourier analysis of torque curves. The value of H_k/H_cJ decreased as the temperature rose. Above room temperature, K_u2/K_u1 increased rapidly with the rise of the temperature and H_k/H_cJ decreased in order of x = 0, 0.1–0.2, and 0.3–0.4 as K_u2/K_u1 increased. Uniaxial anisotropy term (K_u1 + K_u2) has an effect on the orientation in the direction of easy magnetization. On the other hand, biaxial anisotropy term K_u2 has two different directions of easy magnetization. According to the calculation using the equation of magnetic torque for a hexagonal crystal, the direction of the easy magnetization is widely distributed as the value of K_u2/K_u1 increases. An excessive increase in K_u2/K_u1 is not necessarily effective to increase H_k/H_cJ.

The effects of replacing Nd by rare-earth mixture Nd_0.76Pr_0.24, which is equivalent to didymium, and hydrogen desorption rate at the early stage of desorption-recombination process on magnetic properties of HDDR Nd-Fe-B powders were studied. It was found that the Pr-substituted powder produced by a very slow desorption speed exhibits the same coercivity H_cJ and approximately 8% higher remanence B_r compared with the powder of pure Nd system prepared by the conventional desorption speed. Although corrosion resistance of the Pr-substituted powder is slightly inferior to that of the pure Nd system powder, it was confirmed that the Pr substitution does not strongly affect irreversible flux losses of the injection-molded bonded magnet fabricated from the powder after exposure to air at 100°C. These results indicate that didymium can be used as an alternative of the pure Nd to produce the HDDR powders. It is also expected that the usage of didymium can reduce the material cost eliminating the process for the separation of the rare-earth elements.

Law of approach to ferromagnetic saturation (LAS) can be applied to isotropic magnet samples having either uniaxial anisotropy or cubic symmetry. Using the magnetization curves of samples, the relationships between polarization (J) and (1/H², H; applied field) or between susceptibility (dJ/dH) and (1/H³) are able to obtain. The magnetic anisotropy field (H_a) and saturation polarization (J_s) can be calculated using the slope and the intercept in the obtained relation lines. We found that the obtained J_s and H_a using above two relationships agree well when the applied field for magnetization measurements is sufficiently large that corresponds to the H_a of measured sample, >2.0 MA/m for Sr-ferrite. The above result was tried to apply to high anisotropy sample of newly developed (Nd_0.7Zr_0.3)(Fe_0.75Co_0.25)_11.5Ti_0.5N_1.3 having ThMn₁₂ structure, and it was confirmed that the applied field (H_appl) of more than about 6.7 MA/m gave the nearly same J_s and H_a of 1.67 T and 5.85 MA/m, respectively, using the above two relationships.