Mössbauer studies of nano-sized aluminum-substituted maghemites

Several Al-maghemites prepared from Al-lepidocrocites have been studied by Mossbauer spectroscopy from 6 to 300 K, and also at 4.2 K with an applied field of 6 T. A linear decrease in the A and B site fields at 4.2 K for samples containing up to 10% of aluminum suggests a limit for the substitution. The importance of applied-field measurements for a correct characterization of small-particle maghemite is also shown.