They excite Mn2Au thin films with phase-locked single-cycle terahertz electromagnetic pulses and monitor the spin response with femtosecond magneto-optic probes. They observe signals whose symmetry, dynamics, terahertz-field scaling and dependence on sample structure are fully consistent with a uniform in-plane antiferromagnetic magnon driven by field-like terahertz NSOTs with a torkance of (150 ± 50) cm2 A−1 s−1. Their research indicates that fully coherent Néel-vector switching by 90° within 1 ps is within close reach.
A joint publication with Tobias Wagner and Helen Gomonay about coupling of ferromagnetic and antiferromagnetic spin dynamics in Mn2Au/NiFe thin film bilayers has been published in Physical Review Letters.
They investigate magnetization dynamics of Mn2Au/Py (Ni80Fe20) thin film bilayers using broadband ferromagnetic resonance (FMR) and Brillouin light scattering spectroscopy. Their model reveals the dependence of the hybrid modes on the AFMR frequencies and interfacial coupling as well as the evanescent character of the spin waves that extend across the Mn2Au/Py interface.
They reveal the emergence of large photocurrents of spin in collinear Mn2Au, whose properties can be understood as a result of a non-linear optical version of the spin Hall effect, which they refer to as the photospin Hall effect, encoded into the relation between the driving charge and resulting spin photocurrents. Moreover, they suggest that even a very small canting in Mn2Au can give rise to colossal spin photocurrents that are chiral in flavor. They conclude that the combination of staggered magnetization with the structural and electronic properties of this material results in a unique blend of prominent
photocurrents, which makes Mn2Au a unique platform for advanced optospintronics applications.
You can find the publication under APL Mater 11, 071106.
They report direct measurements of the electronic structure of single-crystalline thin films of tetragonal CuMnAs using angle-resolved photoemission spectroscopy (ARPES), including Fermi surfaces (FS) and energy-wavevector dispersions. This work underscores the need to control the chemical potential in tetragonal CuMnAs to enable the exploration and exploitation of the Dirac fermions with tunable masses, which are predicted to be above the chemical potential in the present samples.
You can find the publication under npj Quantum Materials volume 8, Article number: 19 (2023).
They describe how magnon eigenmodes in easy-plane antiferromagnetic insulators are linearly polarized and are not expected to carry any net spin angular momentum. Motivated by recent nonlocal spin transport experiments in the easy-plane phase of hematite, they perform a series of micromagnetic simulations in a nonlocal geometry at finite temperatures. They show that by tuning an external magnetic field, they can control the magnon eigenmodes and the polarization of the spin transport signal in these systems. They argue that a coherent beating oscillation between two orthogonal linearly polarized magnon eigenmodes is the mechanism responsible for finite spin transport in easy-plane antiferromagnetic insulators. The sign of the detected spin signal is also naturally explained by the proposed coherent beating mechanism. Their finding opens a path for on-demand control of the spin signal in a large class of easy-plane antiferromagnetic insulators.
You can find the publication under Phys. Rev. B 107, 184404 (2023).
They demonstrate the combined generation of broadband and narrowband magnons in thin films of NiO/Pt. They present two excitation processes which both lead to the emmision of THz signals. These results open new routes towards the development of fast opto-spintronic devices based on antiferromagnetic materials.
You can find the publication under nature.com/articles/s41467-023-37509-6.
They describe that antiferromagnetic transition metal oxides are an established and widely studied materials system in the context of spin-based electronics, commonly used as passive elements in exchange bias-based memory devices. Currently, major interest has resurged due to the recent observation of long-distance spin transport, current-induced switching, and THz emission. As a result, insulating transition metal oxides are now considered to be attractive candidates for active elements in future spintronic devices. They discuss some of the most promising materials systems and highlight recent advances in reading and writing antiferromagnetic ordering. This article aims to provide an overview of the current research and potential future directions in the field of antiferromagnetic insulatronics.
You can find the publication under Appl. Phys. Lett. 122, 080502 (2023).
They describe that the magnetically ordered phases of the Mn5Si3 crystal are proving to be prototypes for the study of the new fundamental spin physics related to the spontaneous breaking of the time-reversal symmetry despite a zero net magnetization. Here, they report on a route to grow epitaxial Mn5Si3 thin films on Si(111). The growth pathways and structural properties of the manganese silicides can be rationalized in terms of reactions maximizing the free-energy lowering rate. Moreover, they found that the magnetic and the magnetotransport properties can be used as an efficient tool to track both Mn5Si3 crystallinity and proportion in the deposited layers.
You can find the publication under Phys. Rev. Materials 7, 024416 (2023).
They demonstrate that external magnetic fields change the magnetic anisotropy in the antiferromagnet CoO. THis is shown by measuring hysteresis curves for magnetic fields higher than the spin flop field. This behavior is shown to agree with the presence of the unquenched orbital momentum, which can play an important role in antiferromagnetic spintronics.
You can find the publication under PhysRevB.107.L060403.
They observe a spontaneoeus anomalous Hall signal without external magnetic fields in the semiconductor MnTe. The anomalous Hall effect arises from an unconventional phase with strong time-reversal symmetry breaking and alternating spin polarization in real-space crystal structure and momentum-space electronic structure.
You can find the publication under PhysRevLett.130.036702