Strong antiferromagnetic interlayer exchange coupling across an insulating spacer is in increasing demand for high-density magnetic recording. We report here on the interlayer exchange coupling of epitaxial Fe(8 nm)/Si(t)/Fe(10 nm) trilayers as a function of Si thickness studied by ferromagnetic resonance (FMR), Brillouin light scattering, and magneto optic Kerr effect (MOKE) measurement techniques. A very strong anti, ferromagnetic (AFM) interlayer exchange coupling (> 6 erg/cm(2)) was observed at a spacer Si thickness of 0.7 nm. The bilinear J(1) and biquadratic J(2) coupling constants were determined from (i) the fitting of the angular variation of the resonance field (H-res) in FMR experiments, (ii) the field variation of the frequencies of the Damon-Eshbach surface modes (both optic and acoustic) in BLS measurements, and (iii) the fitting of longitudinal MOKE hysteresis loops. We obtain a higher H-res along the easy axis than along the hard axis and the magnetizations of the two Fe films are canted. The eightfold-like symmetry of H-res as a function of the angle observed at room temperature is due to the competition between the Fe fourfold anisotropy and AFM interfacial coupling energy. This behavior vanishes at low temperatures due to a strong increase of AFM coupling (especially J(2)) in comparison to fourfold in-plane anisotropy. From the fitting of the temperature dependent FMR data, we obtain the temperature variation of the bilinear and biquadratic exchange coupling constants. We distinguish the existence of canted magnetization states at resonance by fitting the experimental H-res versus theta(H) data to the model calculation. (C) 2003 American Vacuum Society.