Tailoring the magnetic exchange interaction in MnBi_2Te_4 superlattices via the intercalation of ferromagnetic layers

The intrinsic magnetic topological insulator MnBi_2Te_4 (MBT) provides a platform for the creation of exotic quantum phenomena. Novel properties can be created by modification of the MnBi_2Te_4 framework, but the design of stable magnetic structures remains challenging. Here we report ferromagnet-intercalated MnBi_2Te_4 superlattices with tunable magnetic exchange interactions. Using molecular beam epitaxy, we intercalate ferromagnetic MnTe layers into MnBi_2Te_4 to create [(MBT)(MnTe)_ m ]_ N superlattices and examine their magnetic interaction properties using polarized neutron reflectometry and magnetoresistance measurements. Incorporation of the ferromagnetic spacer tunes the antiferromagnetic interlayer coupling of the MnBi_2Te_4 layers through the exchange-spring effect at MnBi_2Te_4/MnTe hetero-interfaces. The MnTe thickness can be used to modulate the relative strengths of the ferromagnetic and antiferromagnetic order, and the superlattice periodicity can tailor the spin configurations of the synthesized multilayers. The magnetic exchange interaction of MnBi_2Te_4—an intrinsic magnetic topological insulator—can be tuned by intercalating ferromagnetic layers of MnTe.