High-field spin–lattice relaxation of cobalt nuclear spins in iron determined by nuclear orientation

Abstract

In order to resolve the discrepancy in the various estimates of the spin–lattice relaxation rate for cobalt spins in iron, we have remeasured the relaxation time for 60Co spins using both magnetic resonance on the oriented spin system and a non-resonant method in which the lattice temperature is changed rapidly by fast demagnetization. The latter technique yields a value for the relaxation rate (γN2T1T)−1 = (0.43 ± 0.01) × 10−7 s G2 K−1 in an applied field of 3.2 kOe. Based on experimental results and theory, a proposal is made that there exists a field-dependent contribution to the relaxation rate even in the magnetically saturated state. Agreement is then found with NMR measurements on 59Co in iron. The resonant nuclear orientation experiment gives a result which is in doubt because of lack of knowledge of the initial conditions produced after the resonant destruction of the γ-ray anisotropy.