  We report an experimental approach to making multifilament coated conductors
with low losses in applied time-varying magnetic field. Previously, the
multifilament conductors obtained for that purpose by laser ablation suffered
from high coupling losses. Here we report how this problem can be solved. When
the substrate metal in the grooves segregating the filaments is exposed to
oxygen, it forms high resistivity oxides that electrically insulate the stripes
from each other and from the substrate. As the result, the coupling loss has
become negligible over the entire range of tested parameters (magnetic field
amplitudes B and frequencies f) available to us.
