REORIENTATIONAL TRANSITION OF THE MAGNETIC-ANISOTROPY AND ANTIFERROMAGNETIC COUPLING OF CO CR(001) SUPERLATTICES/

We have measured the magnetic anisotropy of high quality Co/Cr(001) su perlattices as a function of the Co thickness using the magneto-optica l Kerr effect (MOKE) and a torsion magnetometer. The samples grown by molecular beam epitaxy exhibit a reorientational transition of the eas y axis from in-plane for large Co thicknesses (t(Co)greater than or eq ual to 14 Angstrom) to out-of-plane for 10 Angstrom less than or equal to t(Co)less than or equal to 14 Angstrom and back again to the in-pl ane orientation for t(Co)less than or equal to 10 Angstrom. We provide evidence that this reorientational transition of the magnetization di rection is due to a sign change of the interface anisotropy constant i nduced by a concomitant structural phase transition of the. Co layers from hcp to bcc with decreasing Co layer thickness. We have observed a ntiferromagnetic alignment of the Co layer magnetization both for in-p lane and perpendicular magnetic anisotropy. The first maximum of the a ntiferromagnetic interlayer interaction occurs at t(Cr)=6 Angstrom, wh ich is in a good agreement with the results for Fe/ Cr(001). In order to theoretically describe the spin structure of the antiferromagnetic coupled multilayers we have performed absolute minima calculations of the angle dependent anisotropy energy. In contrast to trilayer systems we found highly asymmetric spin structures in the superlattices durin g the remagnetization process. (C) 1996 American lnstitute of Physics.