A linear reciprocating electromagnetic machine has an outer stator member having axially spaced apart pole pieces, an open-slot coil cavity housing a coil, and an inner stator member spaced from the outer stator member and providing means for completing a path for magnetic flux. The machine also includes a permanent magnet plunger arranged for reciprocation with respect to the stator members and within the space between such stator members. The plunger is provided with three permanent magnet segments arranged axially along the plunger such that the interface zones between the magnet segments are substantially within the region defined by the stator pole pieces for all operating axial positions of the plunger. The two outer magnet segments are of equal axial length while the center magnet segment is axially longer than an outer magnet segment by an amount equal to the axial length of the open slot of the coil cavity.