NUCLEAR ELECTRIC FIELD GRADIENT AT IRON SITES IN CA2FE2O5 AND CA2FEALO5

Mössbauer spectroscopy has been used to determine the nuclear electric-field-gradient (efg) tensor parameters at the Fe3+ sites in Ca2Fe2O5 and Ca2FeAlO5. In all cases to within experimental error, the efg is axially symmetric and the 2 principal axis of the efg is parallel to the crystallographic b axis. Analytic expressions are developed for the relative transition probability of M1 radiation connecting I = 3/2 to I = 1/2 nuclear states for the situation in which the z principal axis of an axially symmetric efg is perpendicular to an internal magnetic field.