  Introducing magnetic order into a topological insulator (TI) system has been
attracting much attention with an expectation of realizing exotic phenomena
such as quantum anomalous Hall effect (QAHE) or axion insulator states. The
magnetic proximity effect (MPE) is one of the promising schemes to induce the
magnetic order on the surface of TI without introducing disorder accompanied by
doping magnetic impurities in TI. In this study, we investigate the MPE at the
interface of a heterostructure consisting of a topological crystalline
insulator (TCI) SnTe and Fe by employing polarized neutron reflectometry. The
ferromagnetic order penetrates $\sim$ 3 nm deep into the SnTe layer from the
interface with Fe, which persists up to room temperature. Our findings
demonstrate that the interfacial magnetism is induced by the MPE on the surface
of TCI preserving the coherent topological states, which is essential for the
bulk-edge correspondence, without introducing disorder arising from a random
distribution magnetic impurities. This opens up a way for realizing next
generation electronics, spintronics, and quantum computational devices by
making use of the characteristics of TCI.
