Magnetic and structural properties of Co/CoO bilayers

The magnetic and structural properties of Co/CoO bilayers prepared by sputtering have been studied in films with Co thickness in the range of 65 to 250 A. A two‐phase structure consisting of hcp Co and fcc CoO was observed in the films. The coercivity was found to change inversely proportional to the Co thickness and to the sputtering rate. The highest Hc (9 kOe) was obtained in films exposed to ambient conditions for long periods of time. A shift in the hysteresis loop was found in field‐cooled samples, indicating a strong exchange coupling between the Co and CoO phases.