arXiv subjects

Pietro Diona

Publications and source records attributed to Pietro Diona.

3 recordsLinked to original sources

arXiv2026

Deterministic control of antiferromagnetic domain walls by circular phonons

In an antiferromagnet, areas with different orientations of the antiferromagnetic Néel vector, which plays the role of the order parameter, can coexist, thus forming antiferromagnetic domains separated by domain walls. This suggests that antiferromagnets can possess the functionalities of magnetic storage media. Whether one can benefit from these functionalities crucially depends on the availability of efficient means for deterministic control of antiferromagnetic domain walls. Here, we demonstrate an approach to deterministically control domain walls in the van der Waals antiferromagnet Ni-doped $MnPS_3$ via dynamic engineering of the crystal lattice. By resonantly exciting a pair of nearly degenerate orthogonal infrared-active $A_u$ and $B_u$ phonon modes with circularly polarized mid-infrared light, we induce helicity-dependent reconfiguration of 180° antiferromagnetic domains, providing evidence for a phonon-induced effective field conjugate to the Néel order parameter. The domain kinetics exhibit a pronounced helicity asymmetry governed by the interplay between domain-wall elasticity and defect-mediated pinning, enabling small phonon-driven perturbations to accumulate into stable domain transformations. Our results establish dynamic lattice control and defect engineering as means for deterministic control of antiferromagnetic order.

cond-mat.mtrl-sci↗

arXiv2026

Nucleation instability preempts relativistic domain wall transport in high-exchange ferrimagnetic nanowires

Current-driven domain wall motion in ferrimagnets can approach the spin-wave velocity, giving rise to relativistic-like dynamics. While this regime has been experimentally observed in crystalline ferrimagnetic garnets and amorphous GdFeCo, the material conditions that determine whether it can be accessed remain unresolved. Here, we investigate spin-orbit-torque-driven domain wall motion in high-exchange GdCo nanowires using magneto-optical Kerr effect microscopy. We find that nucleation preempts relativistic transport. In GdCo, no velocity saturation or high-field collapse is observed. Instead, the large exchange interaction raises the maximum spin-wave group velocity to $\approx 7\text{--}9~\mathrm{km/s}$, far above the experimentally accessible domain wall velocities. Before this limit can be approached, increasing current density and in-plane magnetic field induce domain nucleation, disrupting steady-state propagation. We map the boundary separating domain wall transport from nucleation instability and show that the nucleation threshold decreases with pulse duration, consistent with thermally assisted barrier crossing. These results identify nucleation as the mechanism that prevents access to the relativistic regime in high-exchange ferrimagnets and establish a dynamical phase boundary between steady propagation and nucleation.

cond-mat.mtrl-sci↗

arXiv2025

Observation of relativistic domain wall motion in amorphous ferrimagnets

Domain walls in ferrimagnets and antiferromagnets behave as relativistic sine-Gordon solitons with the spin-wave group velocity setting the ultimate velocity of domain walls and speed of magnetic devices. While this relativistic regime has been achieved in crystalline ferrimagnets, they cannot be routinely integrated in devices. To enable technological breakthroughs, relativistic dynamics must be demonstrated in easy-to-integrate ferrimagnets such as rare-earth -- transition-metal alloys. However, this scenario remains elusive due to the inherent magnetic disorder of these materials, complex spin-wave spectra, and challenges in modeling their ultrafast dynamics. Here, we demonstrate relativistic domain wall motion in amorphous ferrimagnetic GdFeCo devices operated in the proximity of the angular momentum compensation point. The current-induced domain wall velocity saturates within 10% of the spin-wave speed of 2 km/s, a behavior consistent with relativistic model of domain wall motion. Our observation of relativistic dynamics in technologically relevant ferrimagnets opens the way to magnetic devices operating at the ultimate speed limit.

cond-mat.mtrl-sci↗