Topological Antiferromagnetic Phase of Ni-Intercalated Bi2Te3 in Sputtered Topological Insulator/Ferromagnet-Bi2Te3/Ni80Fe20 Heterostructures

The MBi₂Te₄ (M = Mn, Ni, Eu, V) family of compounds has recently shown promise as an intrinsic magnetic topological insulator (MTI), capable of supporting the quantum anomalous Hall (QAH) effect. Here, we report: (i) Growth of high-quality c-axis oriented TI, Bi₂Te₃ (BT) using sputtering; (ii) Emergence of an interfacial topological antiferromagnetic (AFM) phase when BT is coupled with ferromagnetic materials (FM) such as Ni₈₀Fe₂₀ (Py) [1] and Ni_xZn_y(FeO₂)_z (NiZn-Fr) [2]. Ni diffuses across the interface and forms a Ni-intercalated BT (Bi₂Te₃:Ni) phase. Magnetic hysteresis loop measured at 6K revealed a significant exchange bias (EB) of ~80 Oe and ~5 Oe in BT/Py and BT/TiOx/NiZn-Fr heterostructures confirming FM/AFM interaction. The observation of EB was supported by evidence of AFM order using polarized neutron reflectometry in the Bi2Te3:Ni layer. Cross-sectional chemical analysis using EELS and XPS techniques showed evidence of solid-state reaction between Ni and BT to form Ni-Te bonds. The Neél temperature of the AFM phase was ~63 K, which is higher than that of typical magnetic TIs (MTI). These results pave the way for the exploration of topological phases in CMOS-process-compatible sputtered TI/FM heterostructures and interfaces.