Nanocrystal soft magnetic materials in this description include nanocrystals having the crystallite diameter calculated by the Scherrer's equation based on the half width of the diffraction peak of the X-ray diffraction that is less than 1 μm. In the present embodiment, the crystallite diameter of nanocrystals, which is calculated by the Scherrer's equation based on the half width of the diffraction peak of the X-ray diffraction, may be 100 nm or less and may be 50 nm or less. In some embodiments, the crystallite diameter of nanocrystals is 5 nm or more. Such a size of the crystallite diameter of nanocrystals improves the soft magnetic characteristics. Note here that conventional magnetic steel sheets have a crystallite diameter in the order of μm, typically 50 μm or more.

As is clear from reference examples described later, amorphous soft magnetic materials have tensile strength higher than that of nanocrystal soft magnetic materials. Amorphous soft magnetic materials have saturated magnetization lower than that of nanocrystal soft magnetic materials.

The inner bridges 36 and outer bridges 38 as the bridges of the rotor core 30 structurally have a low strength as stated above. The bridges of the present embodiment are strong because the bridges are made of an amorphous soft magnetic material that is stronger than the nanocrystal soft magnetic material. This suppresses damage at the bridges when the rotor rotates at a high speed, and so the durability of the rotor improves.

Amorphous soft magnetic materials have saturated magnetization lower than that of nanocrystal soft magnetic materials. Magnetic flux from a magnet therefore easily flows to the stator through the parts other than the bridges, and the output characteristics of the motor 1 improve.