Symmetry-Driven Spin-Wave Gap Modulation in Nanolayered SrRuO₃/SrTiO₃ Heterostructures: Implications for Spintronic Applications

Abstract

A strong correlation between magnetic interaction and topological symmetries leads to unconventional magneto-transport behavior. Weyl fermions induce topologically protected spinmomentum locking, which is closely related to spin-wave gap formation in magnetic crystals. Ferromagnetic SrRuO3, regarded as a strong candidate for Weyl semimetal, inherently possesses a nonzero spin-wave gap owing to its strong magnetic anisotropy. In this paper, we propose a method to control the spin-wave dynamics by nanolayer designing of the SrRuO3/SrTiO3 superlattices. In particular, the six-unit-cell-thick SrRuO3 layers within the superlattices undergo a phase transition in crystalline symmetry from orthorhombic to tetragonal, as the thickness of the SrTiO3 layers is modulated with atomic-scale precision. Consequently, the magnetic anisotropy, anomalous Hall conductivity, and spin-wave gap could be systematically manipulated. Such customization of magnetic anisotropy via nanoscale heterostructuring offers a novel control knob to tailor the magnon excitation energy for future spintronic applications, including magnon waveguides and filters. Our nanolayer approach unveils the important correlation between the tunable lattice degrees of freedom and spin dynamics in topologically non-trivial magnetic materials.

Atomistic Engineering of Phonons in Functional Oxide Heterostructures

“…of the superlattices was controlled utilizing a customized automatic laser pulse control system. [ 35 , 36 , 45 , 46 , 47 ] X‐ray diffraction (XRD) θ –2 θ scans showed clear superlattice peaks (± n ) with Pendellösung fringes, indicating atomically well‐defined supercell structures (Figure 2a,b ). The XRD reciprocal space maps, as shown in Figure 2c and Figure S1 , Supporting Information, exhibited fully strained superlattices.…”

Unconventional interlayer exchange coupling via chiral phonons in synthetic magnetic oxide heterostructures

“…SRO/STO superlattices exhibit highly suppressed charge transfer at the interfaces, evidenced by various experiments and theoretical calculations (23)(24)(25). There is no exchange bias effect in the M (H) curves of the SRO/STO superlattices, indicating the absence of extrinsic magnetic pinning layers (Numerous experiments consistently showed no exchange bias in SRO/STO heterostructures (21,(24)(25)(26)(27).). Furthermore, observed phonon modes in the SRO/STO superlattices are octahedral distortionrelated intrinsic phonon modes in the SRO layer, and not defect-induced modes of the NM-I spacer.…”

“…Note that the out-ofplane M (T) shows the conventional FM behaviors of SRO with the same T c and without any downturn, consistent with previous studies (fig. S5) (21,(24)(25)(26)(27). Magnetic field (H)-dependent in-plane magnetization [M (H)] curves of the superlattices consistently support the AFM-like behavior, with a double hysteresis loop and a large coercive field of ~1.8 T appearing below ~80 K (Fig.…”

“…We deliberately grew oxide superlattices with alternating and -atomic unit cells (~0.4 nm) of SRO (t SRO ) and STO (t STO ), respectively, repeated for  times on STO (001) substrates, i.e., [|]  , using pulsed laser epitaxy (see Materials and Methods and figs. S1 to S3) (21,(24)(25)(26)(27). An intriguing oscillation in the in-plane magnetization is observed as a function of t STO , indicating the presence of an unconventional IEC across the NM-I spacer.…”

Tunable Two‐Channel Magnetotransport in SrRuO3 Ultrathin Films Achieved by Controlling the Kinetics of Heterostructure Deposition

“…[ 10 ] It has anomalous Hall transport properties below T C ; SRO can thus be used for spintronic applications. [ 8,11 ] Recent magnetotransport studies of SRO ultrathin films have opened a new avenue in the search for topological phenomena in oxide heterostructures. For example, real‐space topological object (magnetic Skyrmion) has been found in SrIrO 3 /SRO.…”