Magnetic HFI of cerium in an iron garnet investigated by angular correlations

The magnetic HFI of cerium ion in a lanthanum-doped yttrium iron garnet is investigated by the gamma-gamma angular correlation technique. It is found that cerium, formed after radioactive decay of La¹⁴⁰, reaches the ground state of Ce³⁺ in a time short compared with the nuclear state life-time of 4.9 nsec. Quasi-static as well as time-dependent interactions are detected, yielding an internal field ofH _eff=(21.5± 3) kOe at the nuclei of cerium. The molecular field theory is applied in the analysis of data, and values for the exchange field, the spinlattice relaxation time and the magnectic moment of cerium ion in an iron garnet at room temperature are deduced. These values are:H _exch=(147±20)kOe, τ _c =(4.5±0.6)×10^?13 sec and 〈μ_z〉=(0.017±0.002) Bohr magnetons.