An apparatus includes a non-metallic interlayer between a magnetic data storage layer and a heat sink layer, wherein interface thermal resistance between the interlayer and the heat sink layer is capable of reducing heat flow between the heat sink layer and the magnetic data storage layer. The first and second rotor regions are formed of different alloys and the transition zone having a composition that differs from and varies between the first and second rotor regions. Characteristics that may be used to determine the minimum delay period applied include sender characteristics, recipient characteristics, attachment type characteristics and message content type characteristics.