OBSERVATIONS OF MAGNETIZATION REVERSAL AND MAGNETIC CLUSTERS IN COPPER FERRITE FILMS

The observation of a magnetization reversal and a superparamagnetic be havior are reported for films of copper ferrite sputtered in an oxygen atmosphere. X-ray diffraction studies indicate the presence of 14-nm nanoscale crystals of CuFe2O4 in the films. Data on the temperature de pendence of the film magnetization M for zero-field-cooled (ZFC) and f ield-cooled (FC) show that ZFC and FC curves separate at a temperature T(f) and that T(f) decreases with increasing static field strength. F or T< T(f), M vs T data for low fields indicate the presence of a comp ensation point in virgin samples. For T> T(f), a superparamagnetic cha racter is evident form the high-field magnetization data. An average c luster size of 16 nm obtained from such data is in excellent agreement with the results of x-ray diffraction studies.