DIFFUSION OF POSITIVE MUON IN PURE IRON .2. SPIN RELAXATION

Spin relaxation time of positive muon diffusing by means of the hopping and the coherent motions in ferromagnetic b.c.c. Iron is calculated. With decrease of temperature, the relaxation time decreases in proportion to the diffusion constant, but it deviates from this behavior below about 100 K owing to an onset of the coherent motion and finally it again decreases in inverse proportion to a lifetime of band states formed by the coherent motion, whereas the diffusion constant simply turns increasing. The spin in a band state feels a definite magnetic field because of periodic internal fields and sees various fields when scattered to other band states. These scattering processes result in the motional narrowing. A comparison with experiment shows that positive muon in pure Iron performs the coherent motion with a mean-free path being several times as long as the lattice constant. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.