BIQUADRATIC EXCHANGE COUPLING IN SPUTTERED (100)FE CR/FE/

We have used Brillouin light scattering, ferromagnetic resonance, magn eto-optical Kerr effect, and magnetoresistance to investigate interlay er exchange coupling in Fe(40 Angstrom)/Cr(t)/Fe(40 Angstrom) trilayer s grown onto MgO(100) in UHV. Unprecedented strong room-temperature bi quadratic exchange coupling (BEG) was found for values of the Cr thick ness t corresponding to a region where Fe layers are weakly antiferrom agnetically coupled. A common feature in both magnetic and transport m easurements, which we take as a signature of the BEG, is the presence of sudden discontinuous jumps as the external magnetic field is varied . The results are in excellent agreement with model calculations that coherently take into account the same phenomenological parameters char acterizing the anisotropy, Zeeman, and bilinear and biquadratic exchan ge energies.