Stochastische Theorie der magnetischen Relaxation

Abstract

Let a single magnetic dipole be in a constant magnetic field ℏ₀ and a fluctuating field ℏ′(t). For this problem the equation of motion is solved exactly. Averaging the magnetic moment over a convenient ensemble relations of relaxation of a macroscopic system of many spins are obtained. In this way a relaxation tensorΦ for magnetisation is derived from the stochastic properties of the fluctuating field which is a generalization ofKubo's oscillator model. For small timesΦ approaches a Gaußian for large times an exponential function. There are two relaxation times which may be expressed by two correlation times of the fluctuating field. The results give a classification of the absorption line shape in Gaußian and Lorentzian type.