Dynamic Polarization and Relaxation of 75As Nuclei in Silicon at High Magnetic Field and Low Temperature

Abstract

<p>We present the results of experiments on dynamic nuclear polar-<br />ization and relaxation of 75 As in silicon crystals. Experiments are performed<br />in strong magnetic fields of 4.6 T and temperatures below 1 K. At these con-<br />ditions donor electron spins are fully polarized, and the allowed and forbidden<br />ESR transitions are well resolved. We demonstrate effective nuclear polar-<br />ization of 75 As nuclei via the Overhauser effect on the time scale of several<br />hundred seconds. Excitation of the forbidden transitions leads to a polariza-<br />tion through the solid effect. The relaxation rate of donor nuclei has strong<br />temperature dependence characteristic of Orbach process.<br /></p>