STUDY OF DOMAIN-STRUCTURE OF THIN MAGNETIC-FILMS BY POLARIZED NEUTRONREFLECTOMETRY

A technique based on specular reflection of polarised neutrons, comple mented by polarisation analysis and small-angle (diffuse) scattering u nder reflection has been suggested for determination of parameters of domain structure of thin (similar to 10-10(3) nm) films. The generalis ed matrix formalism developed to cope with the problem of reflection o f neutrons from layered magnetic media with magnetisation arbitrary in magnitude and direction allowed to describe the specular reflection f rom unmagnetised films. It has been shown that under total reflection the local (averaged over the region coherently illuminated by a neutro n) magnetic induction, the mean (averaged over the sample) magnetic in duction and the mean square direction cosines of the magnetic inductio n enter into the reflection and depolarisation matrices. It has also b een shown that the first two Fourier transform coefficients of the ang ular distribution function of the domain magnetisation, connected with the mean magnetisation and magnetic texture, can be experimentally fo und. The study of magnetisation processes in Fe36Co64 (170 +/- 3 nm) a nd Co (110 +/- 3 nm) films demonstrates the possibilities of the new t echnique. The optical effect of averaging over the region coherently i lluminated by a neutron, effectively leading to a decrease in the 'loc al' measured magnetic induction of the Co film, has been observed for the first time.