Spindle motor and disk drive apparatus

A spindle motor comprising:

• a stationary portion including a stator;
• and
• a rotating portion rotatably supported by the stationary portion through a lubricating oil;
• wherein
• the stationary portion includes a shaft arranged along a central axis extending in a vertical direction;
• the rotating portion includes:
• a sleeve portion including an inner circumferential surface arranged opposite to an outer circumferential surface of the shaft;
• a hub made of metal, and including a top plate portion extending radially outward from the sleeve portion, and an outer tubular portion extending downward from an outer edge of the top plate portion;
• a magnet made of bonded neodymium fixed to the outer tubular portion, and arranged opposite to the stator with a gap intervening therebetween;
• and
• a cap made of metal, and including an annular plate-shaped portion fixed to an upper surface of the top plate portion;
• the magnet has a coefficient of thermal expansion greater than a coefficient of thermal expansion of the hub;
• and
• the cap has a coefficient of thermal expansion greater than both the coefficients of thermal expansion of the hub and the magnet.