spinmoment

Spinmoment is a term used to describe the intrinsic angular momentum carried by quantum particles due to spin, distinct from orbital angular momentum. For a particle with spin quantum number s, the spin magnitude is |S| = sqrt(s(s+1)) ħ, and the magnetic moment associated with the spin is μ = -g_s μ_B S/ħ, where g_s is the Landé g-factor (approximately 2 for electrons) and μ_B is the Bohr magneton. The projection along a chosen axis is μ_z = -g_s μ_B m_s, with m_s taking values from -s to s. The spin moment thus acts as a source of magnetism in many systems and can be aligned or randomized by external magnetic fields, temperature, and interactions with other spins.

In atoms and solids, spin moments originate from unpaired electron spins in partially filled shells. They contribute to the total magnetic moment of an atom and, through exchange interactions, drive collective phenomena in materials such as ferromagnetism, ferrimagnetism, or antiferromagnetism. The net spin moment per atom in common magnetic elements typically lies in the range of about 0.5 to 3 μ_B, depending on electronic structure and chemical environment.

Measurement and control of spin moments employ techniques such as superconducting quantum interference device magnetometry, electron spin resonance, and X-ray magnetic circular dichroism. In spintronics, spin moments are manipulated and transported as spin currents; related phenomena include spin injection and spin-transfer torque, which underpin devices like magnetic memory and spin-torque oscillators.

Origin and terminology: the concept of spin and its associated moment arises from quantum mechanics and has a well-established theoretical framework. Spinmoment, when used, is typically a stylized reference to the spin magnetic moment rather than a separate physical quantity.