An apparatus may include a ferromagnetic housing defining a housing cavity, an electrically-conductive coil disposed in the housing cavity and defining a coil cavity, a ferromagnetic core piece disposed in the coil cavity, a ferromagnetic pole piece comprising a first face in contact with the core piece and a projection extending from a second face of the pole piece opposite the first face, a flexible element defining an opening, where the projection is disposed within the opening and the flexible element is disposed between a portion of the projection and the first face of the pole piece, and a ferromagnetic armature coupled to the flexible element, where the flexible element is disposed between at least a portion of the armature and the first face of the pole piece.