Final answer:
A magnetic moment in an external static magnetic field both tends to align with the field to minimize energy and may precess around the field with a fixed angle, depending on its quantum mechanical properties. The tendency to align is pronounced in ferromagnetic materials, while precession is a quantum behavior observed in individual magnetic moments.
Step-by-step explanation:
The behavior of a magnetic moment in an external static magnetic field involves precession alongside the tendency to align with the field. When a magnetic moment, such as a bar magnet or an electron with its spin, is subjected to an external magnetic field, it experiences a torque that makes it tend to align with the field to minimize its potential energy. However, due to quantum mechanics and the intrinsic properties of the magnetic moment, it may also precess around the external field rather than aligning perfectly. This precession is the gyromagnetic effect, it occurs at a specific frequency known as the Larmor frequency, and the angle of precession remains fixed during the motion.
Moreover, in materials like ferromagnets, magnetic dipoles can lock together to maintain permanent magnetization after the external magnetic field is removed or reversed, whereas paramagnetic and diamagnetic materials respond differently to external magnetic fields. The interaction of a magnetic moment with an external field is critical in various applications, from magnetic storage devices to electric motors.