As magnetic materials that are used in a sintered ferrite magnet, Ba ferrite, Sr ferrite, and Ca ferrite which have a hexagonal crystal structure are known. Recently, among these magnetic materials, as a magnet material for motors and the like, magnetoplumbite type (M type) Sr ferrite has been mainly employed. The M type ferrite is expressed by, for example, General Formula of AFe12O19. The Sr ferrite has Sr at an A site of the crystal structure.
To improve magnetic characteristics of the sintered ferrite magnet, improvement in the magnetic characteristic is attempted by substituting parts of an A-site element and a B-site element with a rare-earth element such as La, and Co, respectively. For example, Patent Literature 1 discloses a technology of improving a residual magnetic flux density (Br) and a coercive force (HcJ) by substituting parts of the A site and the B site with a specific amount of rare-earth element and Co.
As a representative use of the sintered ferrite magnet, a motor may be exemplified. The sintered ferrite magnet that is used in a motor is demanded to be excellent in both characteristics of the Br and the HcJ. However, generally, it is known that the Br and the HcJ are in a trade-off relationship. Therefore, it has been demanded to establish a technology capable of further improving both characteristics of Br and HcJ.
As an index representing magnetic characteristics in consideration of both characteristics of Br and HcJ, a calculation expression of Br (kG)+⅓HcJ (kOe) is known (for example, refer to Patent Literature 1). As this value is high, it can be said that the sintered ferrite magnet is suitable for a use such as a motor in which high magnetic characteristics are demanded.