@unpublished{21438,
  abstract     = {Antiferromagnets (AFMs) hold promise for applications in digital logic. However, switching AFM domains is challenging, as magnetic fields do not couple to the bulk antiferromagnetic order parameter. Here we show that magnetic-field-driven switching of AFM domains can in many cases be enabled by a generic reduction of magnetic exchange at surfaces. We use statistical mechanics and Monte Carlo simulations to demonstrate that an inequivalence in magnetic exchange between top and bottom surface moments, combined with the enhanced magnetic susceptibility of surface spins, can enable deterministic selection of antiferromagnetic domains depending on the magnetic-field ramping direction. We further show that this mechanism provides a natural interpretation for experimental observations of hysteresis in magneto-optical response of the van der Waals AFM $\mathrm{MnBi_2Te_4}$. Our findings highlight the critical role of surface spins in responses of antiferromagnets to magnetic fields. Furthermore, our results suggest that antiferromagnetic domain selection via purely magnetic means may be a more common and experimentally accessible phenomenon than previously assumed.},
  author       = {Weber, Sophie F. and Sunko, Veronika},
  booktitle    = {arXiv},
  title        = {{Deterministic domain selection of antiferromagnets via magnetic fields}},
  doi          = {10.48550/arXiv.2601.06646},
  year         = {2026},
}

@article{21436,
  abstract     = {The cobalt-intercalated transition metal dichalcogenide CoxTaS2 hosts a rich landscape of magnetic phases that depend sensitively on x. While the stoichiometric compound with x = 1/3 exhibits a single magnetic transition, samples with x≤0.325 display two transitions with an anomalous Hall effect (AHE) emerging in the lower temperature phase. Here, we resolve the spin structure in each phase by employing a suite of magneto-optical probes that include the discovery of anomalous magneto-birefringence: a spontaneous time-reversal sensitive rotation of the principal optic axes. A symmetry-based analysis identifies the AHE-active phase as an anisotropic (2+1)Q state, in which magnetic modulation at one wavevector (Q) differs in symmetry from that at the remaining two. The (2+1)Q state naturally exhibits scalar spin chirality as a mechanism for the AHE and expands the classification of multi-Q magnetic phases.},
  author       = {Kruppe, Jonathon and Rodriguez, Josue and Xu, Catherine and Analytis, James and Orenstein, Joseph and Sunko, Veronika},
  issn         = {2397-4648},
  journal      = {npj Quantum Materials},
  publisher    = {Springer Nature},
  title        = {{Anisotropic multi-Q order in CoxTaS2}},
  doi          = {10.1038/s41535-026-00856-w},
  year         = {2026},
}

@unpublished{21703,
  abstract     = {Altermagnetism has recently emerged as a distinct class of collinear antiferromagnets that break time-reversal symmetry, exhibiting a host of novel properties. Applied strain has attracted particular attention as a key tuning parameter for altermagnets. Although several experimental studies have demonstrated the preparation of single-domain states through a combination of applied strain and magnetic field, the route to such states remains unclear. Here, we use magneto-optical measurements on single crystals of MnTe under applied strain to show that, in contrast to previous reports, strain acts primarily to rotate the Néel vector L continuously. Since the orientation of L determines the magnetic point group symmetry, this continuous rotation effectively tunes the symmetry and its associated physical properties. Furthermore, we demonstrate that built-in strain in free-standing crystals is sufficient to pin L into continuous textures over millimeter length scales. Together, these results provide guidance for future device design and open the door to leveraging the Néel vector orientation as a tunable degree of freedom in spintronic applications.},
  author       = {Alex Liebman-Peláez, Alex Liebman-Peláez and Kruppe, Jon and Regmi, Resham Babu and Ghimire, Nirmal J. and Sun, Yue and Mazin, Igor I. and Noad, Hilary M. L. and Analytis, James and Sunko, Veronika and Orenstein, Joseph},
  booktitle    = {arXiv},
  title        = {{Strain continuously rotates the Néel vector in altermagnetic MnTe}},
  doi          = {10.48550/arXiv.2604.07653},
  year         = {2026},
}

@article{21872,
  abstract     = {Magneto-optic Kerr effect (MOKE) is a powerful probe of broken time-reversal symmetry (T), typically used to study ferromagnets. While MOKE has been observed in some antiferromagnets (AFMs) with vanishing magnetization, it is often associated with structures whose symmetry is lower than basic collinear, bipartite order. In contrast, theory predicts a mechanism for MOKE intrinsic to all AFMs of A-type, i.e. layered AFMs in which ferromagnetic layers are antiferromagnetically aligned. Here we report the experimental confirmation of this mechanism in a bulk AFM. We achieve this by measuring the imaginary component of MOKE as a function of photon energy in MnBi2Te4, an A-type AFM where T is preserved in combination with a translation, and comparing the experimental results with model calculations. Our model suggests that observable MOKE should be expected in all collinear A-type AFMs with out-of-plane spin order, thus enabling optical detection of AFM domains and expanding the scope of MOKE to few-layer AFMs.},
  author       = {Sunko, Veronika and Ahsanullah, Salman and Jain, Vivek and Weber, Sophie and Kumaran, Sivaloganathan and Yan, Jiaqiang and Orenstein, Joseph and Ovchinnikov, Dmitry},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  publisher    = {Springer Nature},
  title        = {{Magneto-optical Kerr effect in an A-type antiferromagnet}},
  doi          = {10.1038/s41467-026-72577-4},
  year         = {2026},
}

@misc{21422,
  author       = {Sunko, Veronika},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{Data underpinning "Magneto-optical Kerr effect in an A-type antiferromagnet"}},
  doi          = {10.15479/AT-ISTA-21422},
  year         = {2026},
}

@unpublished{21435,
  abstract     = {Multiferroic materials, in which electric polarization and magnetic order coexist and couple, offer rich opportunities for both fundamental discovery and technology. However, multiferroicity remains rare due to conflicting electronic requirements for ferroelectricity and magnetism. One route to circumvent this challenge is to exploit the noncollinear ordering of spin cycloids, whose symmetry permits the emergence of polar order. In this work, we introduce another pathway to multiferroic order in which strain generates polarization in materials that host nonpolar spin spirals. To demonstrate this phenomenon, we chose the spin spiral in the well-studied helimagnet Cr1/3NbS2. To detect the induced polarization, we introduce the technique of magnetoelectric birefringence (MEB), an optical probe that enables spatially-resolved and unambiguous detection of polar order. By combining MEB imaging with strain engineering, we confirm the onset of a polar vector at the magnetic transition, establishing strained Cr1/3NbS2 as a type-II multiferroic.},
  author       = {Sun, Y. and Ahn, Y. and Sapkota, D. and Arachchige, H. S. and Xue, R. and Mozaffari, S. and Mandrus, D. G. and Zhao, L. and Orenstein, J. and Sunko, Veronika},
  booktitle    = {arXiv},
  title        = {{Strain-induced multiferroicity in Cr1/3NbS2}},
  doi          = {10.48550/arXiv.2510.11619},
  year         = {2025},
}

@unpublished{21437,
  abstract     = {Altermagnets are a class of collinear magnets that exhibit non-relativistic spin splitting (NRSS) of electronic bands in the absence of net magnetization. Their potential to generate large spin polarization without spin-orbit coupling has created strong interest in probes that access the underlying order parameter directly. In this Perspective, we show that linear magneto-birefringence (LMB) provides a natural and broadly applicable route to detecting altermagnetic order. Building on the correspondence between the momentum-space structure of NRSS and the ferroic ordering of magnetic multipoles in real space, we demonstrate how $d$-wave and $g$-wave NRSS textures yield distinct LMB responses. We present a symmetry-based framework that identifies the optical geometries and field configurations required to isolate specific multipole components, enabling domain imaging and providing benchmarks for theoretical models of LMB.},
  author       = {Sunko, Veronika and Orenstein, J.},
  booktitle    = {arXiv},
  title        = {{Linear magneto-birefringence as a probe of altermagnetism}},
  doi          = {10.48550/arXiv.2511.16421},
  year         = {2025},
}