  The neutron electric dipole moment (EDM) is a sensitive probe for currently
undiscovered sources of charge-parity symmetry violation. As part of the TRIUMF
Ultracold Advanced Neutron (TUCAN) collaboration, we are developing spin
analyzers for ultracold neutrons (UCNs) to be used for a next-generation
experiment to measure the neutron EDM with unprecedented precision. Spin-state
analysis of UCNs constitutes an essential part of the neutron EDM measurement
sequence. Magnetized iron films used as spin filters of UCNs are crucial
experimental components, whose performance directly influences the statistical
sensitivity of the measurement. To test such iron film spin filters, we propose
the use of polarized cold-neutron reflectometry, in addition to conventional
UCN transmission experiments. The new method provides information on iron film
samples complementary to the UCN tests and accelerates the development cycles.
We developed a collaborative effort to produce iron film spin filters and test
them with cold and ultracold neutrons available at JRR-3/MINE2 and J-PARC/MLF
BL05. In this article, we review the methods of neutron EDM measurements,
discuss the complementarity of this new approach to test UCN spin filters,
provide an overview of our related activities, and present the first results of
polarized cold-neutron reflectometry recently conducted at the MINE2 beamline.
