Transmission of a polarized neutron beam through the magnetic Co (700 Angst
rom) film on a glass substrate, where the external magnetic held was applie
d at an angle to the sample surface, was analyzed. The following phenomenon
was observed: a neutron beam of ' + - ' spin transition passed through the
sample without refraction at a certain value of the external magnetic held
strength. This effect was used to determine the nuclear potential of a non
magnetic substrate. (C) 2000 Elsevier Science B.V. All rights reserved.