2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session T00: Poster Session III (1pm-4pm PST)
1:00 PM,
Thursday, March 9, 2023
Room: Exhibit Hall (Forum Ballroom)
Sponsoring
Unit:
APS
Abstract: T00.00194 : Antiferromagnetic FeTe2 Phase Formation at the Sb2Te3/Ni80Fe20 Interface
Abstract
Presenter:
Alexandria Will-Cole
(Northeastern University)
Author:
Alexandria Will-Cole
(Northeastern University)
Topological insulators (TIs), specifically Bi1-xSbx alloys and van der Waals chalcogenides X2Q3 (X = Bi, Sb, Bi1-xSbx; Q = Se, Te) with tetradymite structure, have insulating bulk state and 2D metallic surfaces enabled by topologically protected Dirac surface states (TSS).TIs exhibit large charge-to-spin conversion efficiencies, strong spin-momentum locking, and conductive surface states making them ideal for applications in spin-orbit-torque magnetic random access memory magnetic tunnel junction devices. Bilayer TI/ferromagnet (FM) heterostructures are promising for spintronic memory applications due to their low switching energy and therefore power efficiency.Until recently, the reactivity of topological insulators with FM films was overlooked in the spin-orbit-torque literature, even though there are reports that it is energetically favorable for topological insulators to react with transition metals and form interfacial layers.The novel intrinsic topological insulator phase NiBi2Te4 was recently reported at the interface of Bi2Te3/Ni80Fe20 – thus these interfaces can host exciting new topological phases. We fabricated a bilayer TI/FM heterostructure comprised of molecular beam epitaxy grown Sb2Te3 and DC sputtered Ni80Fe20. Broadband ferromagnetic resonance revealed spin-pumping evident by significant enhancement in Gilbert damping likely a signature of the TSS or the presence of large spin-orbit-coupling in the adjacent Sb2Te3, and a reduction in the effective in-plane magnetization. With low temperature magnetometry, exchange bias is observed which is consistent with an exchange interaction between an antiferromagnet (AFM) and an adjacent FM. Upon cross-section high angle annular dark field scanning transmission electron microscopy of the interface between Sb2Te3 and Ni80Fe20 we observed a complex interface with interfacial phase formation. The predominant phase was structurally consistent with a NiTe2-type phase. Density functional theory calculations revealed that the AFM at the interface was due to the NiTe2-type structure with Fe in the Ni-site, specifically an FeTe2-1T phase. This work emphasizes the chemical complexity of TI/FM interfaces. These interfaces may host novel, metastable intrinsic magnetic topological phases and should be studied more in depth.