  Ferrimagnetic GdCo5-xCux alloys exhibiting the effect of Gd- and
3d-sublattice magnetization compensation at defined temperatures were studied
with respect to their use as thermo-reversible permanent magnets (PM). Coercive
fields &#61549;0Hc in the range 0.3 to 1.6 T were measured for annealed single
crystals with x = 1 - 2.2 having compensation points in the vicinity of room
temperature. Two applications of such a thermo-reversible PM, namely a
thermally controlled actuator and a contactless temperature sensor, are
demonstrated.
