High-speed domain wall racetracks in a magnetic insulator

Abstract

Recent reports of current-induced switching of ferrimagnetic oxides coupled to heavy metals have opened prospects for implementing magnetic insulators into electrically addressable devices. However, the configuration and dynamics of magnetic domain walls driven by electrical currents in insulating oxides remain unexplored. Here we investigate the internal structure of the domain walls in Tm3Fe5O12 (TmIG) and TmIG/Pt bilayers, and demonstrate their efficient manipulation by spin–orbit torques with velocities of up to 400 ms−1 and minimal current threshold for domain wall flow of 5 × 106 A cm−2. Domain wall racetracks are defined by Pt current lines on continuous TmIG films, which allows for patterning the magnetic landscape of TmIG in a fast and reversible way. Scanning nitrogen-vacancy magnetometry reveals that the domain walls of TmIG thin films grown on Gd3Sc2Ga3O12 exhibit left-handed Néel chirality, changing to an intermediate Néel–Bloch configuration upon Pt deposition. These results indicate the presence of interfacial Dzyaloshinskii–Moriya interaction in magnetic garnets, opening the possibility to stabilize chiral spin textures in centrosymmetric magnetic insulators.

Interfacial Dzyaloshinskii-Moriya interaction arising from rare-earth orbital magnetism in insulating magnetic oxides

“…Figure 3a shows χ=χ 0 / cos ψ ð Þ versus H x for up-down and down-up DWs in GGG/TmIG (2.4 nm)/Pt (4.0 nm). The data indicate that both DW types are fully Néel at H x = 0, with oppositely oriented moments and hence with the same lefthanded chirality, in agreement with other work 23,24 . The curves in Fig.…”

“…As shown previously 23,24 , the DW chirality is opposite to that expected if the Pt interface were the source, since here the DWs are left-handed despite Pt being on top. This suggests that the iDMI in garnets has a different origin than in metallic ferromagnet/HM systems, since the SOC in Pt would be expected to generate right-handed chirality in the present layer geometry.…”

“…Very recently, iDMI has been discovered in thin films of centrosymmetric insulating iron garnets [23][24][25] , an important class of low-damping magnetic oxides in which its presence had gone undetected for decades despite their ubiquity in magnetics research. Experimental observations of homochiral Néel DWs 23,24,26 and topological Hall-like signals 27,28 in thin-film rare-earth (RE) iron garnets (REIGs) at room temperature suggest that spin-orbit-driven phenomena thought to be restricted to metallic systems might manifest more broadly in insulating magnetic oxides. However, unlike metallic systems in which iDMI stems from SOC in an adjacent HM, experiments in REIGs suggest that a proximate high-SOC layer is not required.…”

Chiral Spin-Wave Velocities Induced by All-Garnet Interfacial Dzyaloshinskii-Moriya Interaction in Ultrathin Yttrium Iron Garnet Films

“…In these samples, the upper surface is either exposed to air or covered by antennas. The observed effect does not change with different adhesion layers [37], which indicates that the DMI does not originate from the top but from the bottom surface of YIG consistent with TmIG/GGG samples reported recently [19][20][21]. The DMI may be enhanced by a heavy metal layer [52,53] on YIG, but consequently the damping will be severely affected [54].…”

“…We report a different type of spin-wave chirality scaled up in ultrathin YIG films, which we attribute to the interfacial Dzyaloshinskii-Moriya interaction (DMI) [17,18]. Very recently, domain wall motion in Tm 3 Fe 5 O 12 (TmIG) on gadolinium gallium garnet (GGG) suggested interfacial DMI consistent with the Rashba effect at oxide-oxide interfaces [19][20][21]. However, independent evidence for the DMI was not provided.…”