Advances in controlling the correlated behaviour of transition metal dichalcogenides have opened a new frontier of many-body physics in two dimensions. A field where these materials have yet to make a deep impact is antiferromagnetic spintronics-a relatively new research direction promising technologies with fast switching times, insensitivity to magnetic perturbations and reduced cross-talk^1-3. Here, we present measurements on the intercalated transition metal dichalcogenide Fe_1/3NbS₂ that exhibits antiferromagnetic ordering below 42 K (refs. ^4,5). We find that remarkably low current densities of the order of 10⁴ A cm^-2 can reorient the magnetic order, which can be detected through changes in the sample resistance, demonstrating its use as an electronically accessible antiferromagnetic switch. Fe_1/3NbS₂ is part of a larger family of magnetically intercalated transition metal dichalcogenides, some of which may exhibit switching at room temperature, forming a platform from which to build tuneable antiferromagnetic spintronic devices^6,7.

Nematic order is the breaking of rotational symmetry in the presence of translational invariance. While originally defined in the context of liquid crystals, the concept of nematic order has arisen in crystalline matter with discrete rotational symmetry, most prominently in the tetragonal Fe-based superconductors where the parent state is four-fold symmetric. In this case the nematic director takes on only two directions, and the order parameter in such 'Ising-nematic' systems is a simple scalar. Here, using a spatially resolved optical polarimetry technique, we show that a qualitatively distinct nematic state arises in the triangular lattice antiferromagnet Fe_1/3NbS₂. The crucial difference is that the nematic order on the triangular lattice is a [Formula: see text] or three-state Potts-nematic order parameter. As a consequence, the anisotropy axes of response functions such as the resistivity tensor can be continuously reoriented by external perturbations. This discovery lays the groundwork for devices that exploit analogies with nematic liquid crystals.

Our understanding of correlated electron systems is vexed by the complexity of their interactions. Heavy fermion compounds are archetypal examples of this physics, leading to exotic properties that weave magnetism, superconductivity and strange metal behavior together. The Kondo semimetal CeSb is an unusual example where different channels of interaction not only coexist, but have coincident physical signatures, leading to decades of debate about the microscopic picture describing the interactions between the f moments and the itinerant electron sea. Using angle-resolved photoemission spectroscopy, we resonantly enhance the response of the Ce f electrons across the magnetic transitions of CeSb and find there are two distinct modes of interaction that are simultaneously active, but on different kinds of carriers. This study reveals how correlated systems can reconcile the coexistence of different modes on interaction-by separating their action in momentum space, they allow their coexistence in real space.

We present the crystal structure, electronic structure, and transport properties of the material YbMnSb2, a candidate system for the investigation of Dirac physics in the presence of magnetic order. Our measurements reveal that this system is a low-carrier-density semimetal with a two-dimensional Fermi surface arising from a Dirac dispersion, consistent with the predictions of density-functional-theory calculations of the antiferromagnetic system. The low temperature resistivity is very large, suggesting that scattering in this system is highly efficient at dissipating momentum despite its Dirac-like nature.

Exchange bias is a property of widespread technological utility, but its underlying mechanism remains elusive, in part because it is rooted in the interaction of coexisting order parameters in the presence of complex magnetic disorder. Here we show that a giant exchange bias housed within a spin-glass phase arises in a disordered antiferromagnet. The magnitude and robustness of the exchange bias emerges from a convolution of two energetic landscapes, namely the highly degenerate landscape of the spin glass biased by the sublattice spin configuration of the antiferromagnet. The former provides a source of uncompensated moment, whereas the latter provides a mechanism for its pinning, which leads to the exchange bias. Tuning the relative strengths of the spin-glass and antiferromagnetic order parameters reveals a principle for tailoring the exchange bias, with potential applications to spintronic technologies.

The theory behind the electrical switching of antiferromagnets is premised on the existence of a well-defined broken symmetry state that can be rotated to encode information. A spin glass is, in many ways, the antithesis of this state, characterized by an ergodic landscape of nearly degenerate magnetic configurations, choosing to freeze into a distribution of these in a manner that is seemingly bereft of information. Here, we show that the coexistence of spin glass and antiferromagnetic order allows a novel mechanism to facilitate the switching of the antiferromagnet Fe_{1/3 + δ}NbS₂, rooted in the electrically stimulated collective winding of the spin glass. The local texture of the spin glass opens an anisotropic channel of interaction that can be used to rotate the equilibrium orientation of the antiferromagnetic state. Manipulating antiferromagnetic spin textures using a spin glass' collective dynamics opens the field of antiferromagnetic spintronics to new material platforms with complex magnetic textures.

The layered square-planar nickelates, Nd_n+1Ni_nO_2n+2, are an appealing system to tune the electronic properties of square-planar nickelates via dimensionality; indeed, superconductivity was recently observed in Nd₆Ni₅O₁₂ thin films. Here, we investigate the role of epitaxial strain in the competing requirements for the synthesis of the n = 3 Ruddlesden-Popper compound, Nd₄Ni₃O₁₀, and subsequent reduction to the square-planar phase, Nd₄Ni₃O₈. We synthesize our highest quality Nd₄Ni₃O₁₀ films under compressive strain on LaAlO₃ (001), while Nd₄Ni₃O₁₀ on NdGaO₃ (110) exhibits tensile strain-induced rock salt faults but retains bulk-like transport properties. A high density of extended defects forms in Nd₄Ni₃O₁₀ on SrTiO₃ (001). Films reduced on LaAlO₃ become insulating and form compressive strain-induced c-axis canting defects, while Nd₄Ni₃O₈ films on NdGaO₃ are metallic. This work provides a pathway to the synthesis of Nd_n+1Ni_nO_2n+2 thin films and sets limits on the ability to strain engineer these compounds via epitaxy.

Correction to: Nature Communicationshttps://doi.org/10.1038/s41467-023-37117-4, published online 16 March 2023 In the Acknowledgements section of this article the grant number relating to NSF was incorrectly given as DMR 2045826 and should have been DMR-2045826. The original article has been corrected.

The rare-earth nickelates possess a diverse set of collective phenomena including metal-to-insulator transitions, magnetic phase transitions, and upon chemical reduction, superconductivity. Here, we demonstrate epitaxial stabilization of layered nickelates in the Ruddlesden-Popper form Ndn+1NinO3n+1 using molecular beam epitaxy. By optimizing the stoichiometry of the parent perovskite NdNiO3, we can reproducibly synthesize the n=1-5 member compounds. X-ray absorption spectroscopy at the O K and Ni L edges indicate systematic changes in both the nickel-oxygen hybridization level and nominal nickel filling from 3d8 to 3d7 as we move across the series from n=1 to ∞. The n=3-5 compounds exhibit weakly hysteretic metal-to-insulator transitions with transition temperatures that depress with increasing order toward NdNiO3 (n=∞).