EVIDENCE FOR AN ANISOTROPY-INDUCED NONCOLLINEAR SPIN-STATE IN EXCHANGE-COUPLED CO CU(001)/

The magnetization behaviour of a Co/Cu/Co(001) sandwich has been studi ed by magneto-optical Kerr effect measurements. The sample was grown b y molecular beam epitaxy onto a sapphire (11.2BAR) substrate with a Cu /Cr/Nb(001) buffer system. The copper layer had the form of a wedge wi th the thickness range chosen to be around the second region of antife rromagnetic exchange coupling. The hysteresis loops in the regime of w eak antiferromagnetic coupling show characteristic steps, which can be explained by an anisotropy-induced non-collinear spin state. Indicati on for a similar behaviour is also found in the regime of strong antif erromagnetic coupling. This behaviour is explained by taking into acco unt the competition between anisotropy, interlayer exchange coupling a nd external field energy. The nature of this metastable non-collinear magnetization state is in marked contrast to the biquadratic (90-degre es) exchange coupling which was discovered in Fe/Cr(001).