Exchange-mediated spin–lattice relaxation of Fe 3+ ions in borate glasses

Abstract

Spin–lattice relaxation times ( T 1) of two borate glasses doped with different concentrations of Fe 2O 3 were measured using the Electron Spin-Echo (ESE) technique at X-band (9.630 GHz) in the temperature range 2–6 K. In comparison with a previous investigation of Fe 3+-doped silicate glasses, the relaxation rates were comparable and differed by no more than a factor of two. The data presented here extend those previously reported for borate glasses in the 10–250 K range but measured using the amplitude-modulation technique. The T 1 values were found to depend on temperature ( T) as T n with n ∼ 1 for the 1% and 0.1% Fe 2O 3-doped glass samples. These results are consistent with spin–lattice relaxation as effected by exchange interaction of a Fe 3+ spin exchange-coupled to another Fe 3+ spin in an amorphous material.