Various embodiments are disclosed for a thermal management system and related method for selectively thermally isolating and thermally connecting a target component. One embodiment of a system includes a first component having a first surface proximate to a target component, and an electromagnet between the first surface and the target component. A second component is spaced apart from the first component to form a gap that serves as a thermal boundary between the first component and the second component. A carrier fluid disposed within the gap includes multiple thermally conductive, ferrous particles. The carrier fluid is configured to align at least a portion of the thermally conductive, ferrous particles when the electromagnet generates a magnetic field that attracts the particles, and to displace at least a portion of the particles when the electromagnet generates a magnetic field that repels the particles.