Coupling of Fe films through a granular magnetic layer

J. GÓMEZ; A. BUTERA; J. L. WESTON

JOURNAL OF APPLIED PHYSICS

Año: 2006 vol. 100 p. 53908 - 53914

0021-8979

We have studied the magnetic coupling between two continuous Fe layers of fixed thickness separated by a granular Fe-SiO2 spacer of varying thickness (1.1 nm< t <18 nm) and composition (0.45 < x < 0.95). We have analyzed the magnetic response with dc magnetization and ferromagnetic resonance FMR. Depending on the characteristics of the Fe-SiO2 layer the hysteresis loops can have a continuous or a  two step process reversal. FMR data show one or two absorption lines, depending on the microwave excitation frequency. From these data we were able to determine that the Fe/Fe interlayer coupling is ferromagnetic with an exchange field in the range of 0.5 kOe <HE <3.5 kOe. The largest coupling occurs for thin spacers and large Fe concentrations. Fe/Fe-SiO2 layers are also coupled ferromagnetically with  an exchange coupling constant that is larger than the Fe/Fe interlayer interaction.