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Magnetic domain walls (DWs) are the finite boundaries that separate the regions of uniform magnetization in a magnetic material. They constitute a key research topic in condensed matter physics due to their intriguing physics and relevance in technological applications. A multitude of spintronic concepts for memory, logic, and data processing applications have been proposed, relying on the precise control of DWs via magnetic fields and electric currents. Intensive research into DWs has also spurred interest into chiral magnetic interactions, topology, and relativistic physics. In this article, we will first review the rapid evolution of magnetic DW research and, in particular, the current-driven DW motion enabled by the improved understanding of DW dynamics and the development of suitable ferrimagnetic thin films. We will then provide an outlook on future directions in DW dynamics research exploiting ferrimagnetic garnets as a tunable material platform.

The interlayer Dzyaloshinskii-Moriya interaction (IL-DMI) has recently emerged as an ingredient promoting chiral orthogonal coupling between adjacent magnetic layers in multilayered systems. IL-DMI offers an additional tuning knob to engineer the magnetic behavior in spintronic devices, which could be useful for nonvolatile logic and memory technologies. Here, we systematically study, via first-principles calculations and the three-site Fert-Lévy model, the spacer thickness dependence of the IL-DMI between an out-of-plane ferrimagnet TbCo and an in-plane ferromagnet Co through Pt, Ir, Pd, and Ru. We observed a damped oscillatory behavior with increasing spacer thickness in all cases with characteristic amplitude and periodicity. Furthermore, we established a direct correlation between the IL-DMI and density of states of bottom and top Co atoms, dominated by the spacer thickness, which is attributed to a hybridization of electronic orbitals. Based on this compelling evidence, we propose that the electronic orbital hybridization contributes to the microscopic origin of the IL-DMI metallic magnetic multilayers. We anticipate that our results will provide insights into the understanding and precise control of IL-DMI in a wide range of materials and spintronic device concepts.

We report the structural, magnetic, and interfacial spin transport properties of epitaxial terbium iron garnet (TbIG) ultrathin films deposited by magnetron sputtering. High crystallinity was achieved by growing the films on gadolinium gallium garnet (GGG) substrates either at high temperature, or at room temperature followed by thermal annealing, above 750 {\deg}C in both cases. The films display large perpendicular magnetic anisotropy (PMA) induced by compressive strain, and tunable structural and magnetic properties through growth conditions or the substrate lattice parameter choice. The ferrimagnetic compensation temperature (TM) of selected TbIG films was measured through temperature-dependent anomalous Hall effect (AHE) in Pt/TbIG heterostructures. In the studied films, TM was found to be between 190-225 K, i.e., approximately 25-60 K lower than the bulk value, which is attributed to the combined action of Tb deficiency and oxygen vacancies in the garnet lattice evidenced by x-ray photoelectron spectroscopy measurements. Sputtered TbIG ultrathin films with large PMA and highly tunable properties reported here can provide a suitable material platform for a wide range of spintronic experiments and device applications.

Spin-orbit torques (SOTs) have emerged as an efficient means to electrically control the magnetization in ferromagnetic heterostructures. Lately, an increasing attention has been devoted to SOTs in heavy metal (HM)/magnetic insulator (MI) bilayers owing to their tunable magnetic properties and insulating nature. Quantitative characterization of SOTs in HM/MI heterostructures are, thus, vital for fundamental understanding of charge-spin interrelations and designing novel devices. However, the accurate determination of SOTs in MIs have been limited so far due to small electrical signal outputs and dominant spurious thermoelectric effects caused by Joule heating. Here, we report a simple methodology based on harmonic Hall voltage detection and macrospin simulations to accurately quantify the damping-like and field-like SOTs, and thermoelectric contributions separately in MI-based systems. Experiments on the archetypical Bi-doped YIG/Pt heterostructure using the developed method yield precise values for the field-like and damping-like SOTs, reaching -0.14 and -0.15 mT per 1.7x$10^{ 11}$ A/$m^2$, respectively. We further reveal that current-induced Joule heating changes the spin transparency at the interface, reducing the spin Hall magnetoresistance and damping-like SOT, simultaneously. These results and the devised method can be beneficial for fundamental understanding of SOTs in MI-based heterostructures and designing new devices where accurate knowledge of SOTs is necessary.

Current-induced spin-orbit torques (SOTs) have emerged as a powerful tool to control magnetic elements and non-uniform magnetic textures such as domain walls and skyrmions. SOT-induced switching of perpendicular magnetization generally requires an external field to break the rotational symmetry of the spin-orbit effective fields responsible for the deterministic reversal. The proposed mechanisms to eliminate this requirement often rely on complex multilayer structures that necessitate laborious optimization in the material and spin transport properties, making them less attractive for applications. Herein, current-induced, external field-free switching of an epitaxial MgO/Pt/Co trilayer with an extremely large perpendicular anisotropy in excess of 3 Tesla is reported. It is found that switching occurs due to the interplay of strong SOTs, local anisotropy fluctuations, and the Dzyaloshinkii-Moriya interaction inherent to this epitaxial system. Given that these layers constitute the base stack of a magnetic tunnel junction, this switching mechanism offers the most technologically viable path toward devices such as field-free SOT-based magnetic random-access memories.