We report bulk magnetic properties of the monoclinic lanthanide tantalates, M ′ − L n TaO 4 ( L n = Tb, Dy, Ho, Er), where the magnetic L n 3 + ions are arranged on a distorted 2D square lattice. The heavier analog M ′ − YbTaO 4 has been investigated as a spin-orbit-coupled, quasi-two-dimensional frustrated magnet, and the properties of the other M ′ − L n TaO 4 are expected to vary depending on the electronic configuration of the L n ion, namely, Kramers vs non-Kramers behavior and different crystal electric field parameters. In this work, powder neutron diffraction is used to confirm the crystal structure for L n = Tb, Ho, Er, and to determine the magnetic structure of M ′ − TbTaO 4 , which displays long-range antiferromagnetic (AFM) order below T N = 2.1 K . The Tb 3 + moments are aligned primarily along the c axis with AFM nearest-neighbor interactions. Susceptibility data suggest that M ′ − DyTaO 4 may display short-range ordering around 2.7 K, while M ′ − HoTaO 4 and M ′ − ErTaO 4 show AFM correlations but do not order above 1.8 K. Measurements of the magnetic specific heat provide evidence for a Kramers doublet ground state in M ′ − ErTaO 4 , similar to its heavier analog M ′ − YbTaO 4 .

It is known that cuprate artificial high- T C superlattices (AHTS) with period d , composed of quantum wells confining interface space charge in stoichiometric Mott insulator layers ( S ), with thickness L , at the interface with overdoped normal metallic cuprate layers ( N ) show a superconducting dome by tuning the geometric L over d ratio of the SNSN superlattice with the top predicted by quantum material design engineering quantum size effects. Here we report high-field magnetotransport measurements up to 41 Tesla of AHTS across the entire superconducting dome. The results show the universal upward-concave behavior of the temperature-dependent upper critical magnetic field in low- T C samples at the rising edge and drop edge of the dome, providing strong evidence consistent with two-band superconductivity in agreement with multigap theory used for quantum design of the SNSN superlattices. The measured superconducting coherence length demonstrates that atomic-scale engineering controls not only the critical temperature but also the intrinsic pair size at Fano-Feshbach resonances physics paving the way toward next-generation quantum devices and shedding light on unconventional superconductivity.

Atomic volume differences determine the structure and phase stability of alloys. To assess the size mismatch, atomic volumes of pure elements, derived from their elemental crystalline states, are normally used as a reference. Using calculations, we show that substitutional transition metal solute atoms in bcc iron or tungsten exhibit sizes substantially different from their elemental volumes. Analysis of electronic structure suggests that the significant oversizing of substitutional solutes in bcc α -iron is caused by the asymmetric filling of electronic states of solute atoms. This produces a strong local magnetovolume effect where, for example, the apparent sizes of platinum and palladium solute atoms are from 35% to 40% larger than their elemental volumes. The analysis of nonlocal variation of electronic structure in the neighborhood of a solute atom shows that in bcc tungsten, the atoms near a substitutional 3 d transition metal solute atom shrink, whereas in bcc iron, atoms next to a substitutional site swell, further increasing the apparent relaxation volume of the solute atom. Constrained magnetic DFT calculations show that manganese, iron, and cobalt solute impurity atoms in tungsten retain their magnetic moments, with collinear spin-flip barriers of 0.20, 0.52, and 0.17 eV, respectively. In other instances, elements like Cr in α -Fe are nominally undersized if the elemental volumes are compared, but in a solute form the relaxation volume of Cr is positive ( + 20 % of its atomic volume), stemming from the electron transfer effect and variation of the effective volume of neighboring host Fe atoms. Simulations suggest that application of strong magnetic field might also affect the relaxation volume of transition metal solutes and their solubility.

When two-dimensional atomic layers of different materials are brought into close proximity to form van der Waals (vdW) heterostructures, interlayer interactions can strongly influence their physicochemical properties. These effects are particularly pronounced when the interface exhibits local order and near-perfect structural alignment, giving rise to moiré patterns. Using density-functional theory calculations, we investigate a bilayer heterostructure composed of hexagonal boron nitride (hBN) and silicon carbide (SiC). We predict that introducing a boron vacancy, V B , at specific lattice sites alters the interlayer interaction from weak vdW coupling to localized silicon-nitrogen covalent bonding. Motivated by this mechanism, we examine the binding of transition-metal adatoms and identify principles for enhancing surface reactivity and stabilizing isolated single-metal atoms. Machine-learning molecular dynamics at finite temperature further demonstrate rapid and effectively irreversible trapping of Cu at V B sites, and show how the V B :Cu ratio governs the transition from single-atom isolation to vacancy-directed aggregation. These results suggest the hBN/SiC heterostructure as a versatile platform for atomically precise transition-metal functionalization, with implications for catalytic energy-conversion materials.