A generator (13A, . . . 13C) of a time-variable magnetic field (B1) of a
magnetic resonance device (1) which has an examination space (9,9A) for
accommodating at least one area to be examined of an examination subject
(7), in which examination area the time-variable magnetic field (B1) is
generated by means of a current through a conductor (15, 19, 31). The
magnetic field lines (23) of the magnetic field (B1) close with the aid
of a field flux return space (17), in which there is arranged at least
one sub-assembly (27) which has magnetizable material. A reduction of a
magnetic energy density in the field flux return space (17) is produced
by this means. This increases e.g. the efficiency i n the generation of
high-frequency magnetic fields (B1) or of gradient fields with the aid of
the conductor (15,19,31).
