  The present Letter describes the magnetocaloric effect of a diamagnetic
material with a magnetic field $B_\parallel$ along the $z$ axis and a
transversal and oscillating field $B_\perp (\ll B_\parallel)$ parallel to the
$x-y$ plane. We show that the magnetocaloric potentials due to a change in
$B_\parallel$ is the same as those due to a change in the frequency of
$B_\perp$. These results raise the possibility of building magnetocaloric
devices without moving parts, since changing frequency is a simple electronic
issue, while changing the field from permanent magnets depends on mechanical
aspects.
