Out-of-plane ferromagnetic-resonance study of magnetically coupled Fe/Cr/Fe films

• Online Access: http://hdl.handle.net/2047/d20002272

Magnetically coupled single-crystal Fe/Cr/Fe (001) sandwiches have been studied by the ferromagnetic resonance (FMR) techniques. Such films have been previously shown to be antiferromagnetically coupled for a chromium layer thickness range 12 Å< tcr < 25 Å by variable frequency ferromagnetic resonance measurements along principal crystallographic axes, and other techniques. These measurements have been extended to include oblique angle application of the applied magnetic field (H) between principal crystallographic axes in the film plane and the film normal. Measured films had tcr = 13, 16, 17, and 28 Å. Ferromagnetic resonance measurements were taken using a fixed frequency 9.5-GHz cavity. Resonances corresponding to the in-phase and out-of-phase precession of film moments M₁ and M₂ were observed for the three thinnest films with H lying in the film place. These resonances could be tracked to high (~85 °) oblique angles before disappearing, with the in-phase resonance strengthening near perpendicular. Perpendicular FMR measurements on the tcr= 13-Å-thick sample show a weaker resonance ~680 Oe above the in-phase resonance, corresponding to the out-of-phase processional mode. This value can be directly compared to 4J/Ms~540 Oe result from earlier work, perhaps indicating some anisotropic exchange. An extension of the model presented in Ref. 1 is presented to explain the resonance behavior as a function of angle.