Hang Khume Tan

Gigahertz excitations of magnetic films are widely explored for energy‐efficient, high‐frequency microelectronics. The advent of nanoscale chiral spin textures (CSTs) with topological dynamics promises novel resonance characteristics. However, prior works on technologically relevant chiral multilayers encountered key material constraints, precluding the realization of functional CST resonances. We address this by engineering a minimally damped, strongly chiral multilayer with a robust broadband resonance spectrum. Microwave spectroscopy, Lorentz microscopy, and simulations elucidate contrasting resonance features on either side of zero magnetic field arising from distinct irreversible CST transitions. A simple analytical model can quantitatively describe these robust inter‐textural resonances over the entire field‐frequency range. Crucially, in situ CST reconfigurability enables analog tunability of the resonant dispersion ‐ with wide‐band, deterministic, non‐linear (or linear) modulation via the input knob. Our work unlocks the microwave potential of multilayer CSTs by leveraging their unique thermodynamics. It opens the door to fabrication‐free reconfigurable magnonics, toward broadband transmission and unconventional computing.

The stability and efficient electrical control of chiral spin textures (CSTs) is critical for their implementation in racetrack device architectures. Three principal properties determine the utility of material platforms for spin-texture dynamics: perpendicular magnetic anisotropy (PMA), Dzyaloshinskii–Moriya interaction (DMI), and spin Hall angle (SHA). Notwithstanding individual studies, a comprehensive benchmarking of these key interactions across racetrack-compatible material systems remains lacking. Here, we systematically evaluate tunnel-readout compatible HM/CoFeB/MgO trilayers fabricated using wafer-scale techniques. Their key properties—PMA, DMI, and SHA—were characterized across four heavy metals (Pt, W, Ta, and Ir) and two CoFeB compositions using magnetometry, spectroscopy, and transport techniques, respectively. Our results reveal that the W-based stacks exhibit robust PMA and high SHA, while the Pt-based stacks provide the strongest DMI. Notably, both DMI and SHA depend strongly on both heavy metal and CoFeB composition, underscoring the critical role of alloy engineering in controlling interfacial magnetic properties. Our work provides quantitative benchmarks and materials design principles for developing next-generation CST-based racetrack devices.

Voltage control of magnetic anisotropy (VCMA) induced by charge accumulation is typically considered as an ultrafast process, enabling energy-efficient and high-speed magnetization switching in spintronic devices. In this work, we investigate the real-time dynamics of VCMA-assisted switching of magnetic tunnel junctions via relaxation in a magnetic field. We show that device-dependent charging effects and magnetic granularity in the free layer limit the switching speed at applied voltages close to the critical switching threshold. Increasing the voltage or the applied magnetic field reduces the incubation delay and total switching time to below a few ns. Micromagnetic simulations incorporating the finite charging times of the tunnel junction and the granularity of the magnetic film reproduce the experimental results, providing critical insights into optimizing VCMA-driven magnetization control for memory and logic applications.

The Mn3Ga material is a promising candidate for memory and computing devices owing to its rich crystalline structures of tunable ferrimagnetic and collinear and non-collinear antiferromagnetic phases. In particular, Mn3Ga with non-collinear antiferromagnetic order exhibits giant anomalous and topological Hall conductivities and is a potential material platform for hosting spin-related quantum phenomena. In this study, we demonstrate Mn3Ga films grown on thermally oxidized Si substrates, with and without the Ta buffer, under different deposition temperatures (Ts). With increasing Ts, the dominant crystalline structure across all Mn3Ga films evolves from a cubic to hybrid tetragonal and hexagonal texture, wherein the crystalline orientation of spins endows the films with in-plane magnetic anisotropy. For Ta/Mn3Ga and Mn3Ga films grown under high Ts, the inhomogeneity in surface energy of the buffer layer results in a non-uniform granular film in the former. Notably, the Mn3Ga films of hexagonal texture exhibit topological Hall signatures. The density functional theory calculations on the hexagonal Mn3Ga phase corroborated with the experimental magnetic, structural, and transport properties. These findings establish an important platform for tailoring Mn3Ga films toward multifunctional applications.

Magnetic skyrmions are promising candidates for computing and memory applications. The static and dynamic behaviors of skyrmions are tunable by altering the interfacial magnetic properties. These interfacial magnetic properties are alterable by modifying the interface structure of thin films. However, the relationship between the structural properties of the interface and the skyrmions properties is not straightforward, and a comprehensive insight is required to facilitate better controllability of the skyrmions’ behaviors. Here, we comprehensively understand the relationship between atomic displacements at the interface and skyrmions’ static behavior. In this study, we used ion irradiation to achieve inter-atomic displacements. We observed that the inter-atomic displacements could tailor the physical properties of skyrmions. We noticed a peculiar increase in the magnetization, Dzyaloshinskii–Moriya interaction, and exchange stiffness. The modifications in magnetic properties reduced the domain wall energy, which enhanced the skyrmion density (by six-folds) and reduced the average skyrmion diameter (by 50%). Furthermore, we compared the observed results of ion irradiation with those from the annealing process (a well-studied method for modifying magnetic properties) to better understand the effect of atomic displacements. Our study provides a route to achieve a highly-dense skyrmion state, and it can be explored further to suppress the skyrmion Hall effect for skyrmion-based applications.