Scattering of polarized soft x-rays is applied to study the magnetic and structural properties of $\mathrm{Co}∕\mathrm{Cu}$ GMR (giant magnetoresistance) layer stacks. The $\mathrm{Co}∕\mathrm{Cu}$ multilayers with layer thicknesses tuned to the second maximum of the GMR show a pronounced series of half-integer-order magnetic Bragg peaks in reflectometry curves measured at the Co $L_{2,3}$ absorption edges. These peaks of purely magnetic origin arise due to the antiparallel alignment of neighboring magnetic layers caused by interlayer exchange coupling. In applied magnetic fields the antiferromagnetic coupling is reduced, as proved by a reduction of the magnetic peaks in both specular and diffuse scattering. The magneto-optical constants at the Co $L$ edges were determined from the energy dependence of the Bragg peak positions and utilized for modeling the scattering curves. Upon magnetization reversal, the reflectometry curves exhibit angular-dependent asymmetry effects, which indicate a high sensitivity of the magnetic signal on the probing depth. Comparison of x-ray magnetic hysteresis loops measured at the one-half and higher-order half-integer Bragg peaks shows that for detailed structural and magnetic information, the higher-order peaks have to be evaluated, too. Through the angular dependence of the hysteresis loops, they can be tuned to show antiferromagnetic and ferromagnetic features separately.

• Received 24 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.054437