Ferromagnetic resonance relaxation has been used to study a series of LPEhyphen;grown YIG films containing calcium in increasing concentrations. The considerably large linewidths revealed that a high population of Fe4+ions is allowed to enter the epilayers. Etching techniques and selective heat treatments provided respectively an insight on the Cahyphen;concentration gradients within the films and a means of confirming the identification of the relaxing ions.
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