Nuclear Magnetic Resonance and Nuclear Relaxation in hcp Cobalt

Abstract

The nuclear spin-lattice and spin-spin relaxation times T 1 , T 2 of Co 59 in domain walls of hcp cobalt have been measured between 1.6 and 700 K by use of spin echo method. The variation of T 1 across domain walls is expressed as T 1 = T 10 /sin 2 θ, where θ is the angle between the electronic spins and the c axis, and T 10 , the shortest relaxation time at the center of walls. T 1 for nuclei in domains satisfies T 1 T =0.17±0.01 sec K, but T 10 shows a deviation from T 10 T =constant, which is believed to be due to the wall-type excitation. The Co 59 NMR in single crystal specimens have also been observed in the magnetic field up to 20 kOe. The field dependence of the electric quadrupole splitting suggests that the 3d charge distribution slightly changes, depending on the direction of electronic spins.