Antiferromagnetic coupling in amorphous Co_xSi_1−x∕Si multilayers

Antiferromagnetic coupling has been observed in amorphous Co_xSi_1−x∕Si multilayers prepared by co-sputtering on Si substrates. X-ray reflectivity measurements show that the multilayer structure is well defined, with cumulative roughness values around 0.8 nm. Alternating gradient magnetometry and magneto-optical transverse Kerr effect measurements show that the films have in-plane uniaxial magnetic anisotropy and that the Co_xSi_1−x layers are antiferromagnetically coupled for Si layer thicknesses lower than 8 nm. The magnetic field required to switch between antiparallel and parallel configurations is as low as 3 Oe. These results are in contrast with those found in reference polycrystalline Co∕Si multilayers, which show no evidence of antiferromagnetic coupling.