A magnetic assembly for use in a housing of an electronic device can include a first and a second magnet and a magnetic shield. The RF electrode is so controlled that a discharge amount of a gas generated therefrom is in the range of 10\u22128 Torr\xb7Lsecond to 10\u22126 Torr\xb7Lsecond. In a variation, the composite also contains a small percentage by weight of flame retardant fibers that impart flame resistant properties to the composite. The sintered structure can have discontinuous regions of shell material between the sintered interfaces. The device further comprises a detectable label coupled to the substrate recognition molecule.