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Abstract Kagome lattice magnets are an interesting class of materials as they can host topological properties in their magnetic and electronic structures. YMn6Sn6 is one such compound in which various exotic magnetic and electronic topological properties have been realized. Here, by means of a partial substitution of Sn with an isovalent and slightly smaller atom Ge, we demonstrate the sensitivity of such chemical substitution on the magnetic structure and its influence in the electronic properties. Magnetic structure of YMn6Sn4Ge2 determined by neutron diffraction reveals an incommensurate staggered magnetic spiral with a slightly larger spiral pitch than in YMn6Sn6. This change in magnetic structure influences the Fermi surface enhancing the out-of-plane conductivity. Such a sensitivity to the partial chemical substitution provides a great potential for engineering the magnetic phases and associated electronic properties not only in YMn6Sn6, but also in the large family of 166 rare-earth kagome magnet.

Abstract Ising superconductivity, observed in NbSe2 and similar materials, has generated tremendous interest. Recently, attention was called to the possible role that spin fluctuations (SF) play in this phenomenon, in addition to the dominant electron–phonon coupling (EPC); the possibility of a predominantly triplet state was discussed and led to a conjecture of viable singlet–triplet Leggett oscillations. However, these hypotheses have not been put to a quantitative test. In this paper, we report first principle calculations of the EPC and also estimate coupling with SF, including full momentum dependence. We find that: (1) EPC is strongly anisotropic, largely coming from the $$K-{K}^{{\prime} }$$ K − K ′ scattering, and therefore excludes triplet symmetry even as an excited state; (2) superconductivity is substantially weakened by SF, but anisotropy remains as above; and, (3) we do find the possibility of a Leggett mode, not in a singlet–triplet but in an s ++ – s ± channel.

The non-monotonic behaviour of the superconducting transition temperature in NbSe2-xSx monolayer alloys has been linked to fractal superconductivity. Here, using first-principles calculations, the authors provide an alternative explanation for this behavior based on the effects of alloying and defects on the electronic structure and magnetism.

The heterointerfacing of different materials with competing magnetic orders forms the basis for today’s spintronic devices, however materials compatibility has remained a major limitation to the conception of new multilayered systems. Here, we uncover a multilayer of competing magnetic orders within a single layer of FeRh after low-energy He-ion irradiation: metamagnetic, ferromagnetic, and spin glass. Polarized neutron reflectometry, irradiation modeling, and density functional theory calculations reveal a direct correlation between the disorder concentration, the depth-dependent magnetic ordering, and the onset of the metamagnetic transition. Such a heterostructure opens the door to new paradigms in antiferromagnetic electronics and ultra-low-power magnetization controllability.

Iron-based superconductors exhibit complex couplings between different electronic degrees of freedom, leading to unusual correlated phases. Ok et al. show that Sr2VO3FeAs develops a hidden order state due to frustrated interactions between the magnetic fluctuations of its SrVO3 and SrFeAs layers.

Recent studies on superconductivity in NbSe_{2} have demonstrated a large anisotropy in the superconducting critical field when the material is reduced to a single monolayer. Motivated by this recent discovery, we use density-functional theory (DFT) calculations to quantitatively address the superconducting properties of bulk and monolayer NbSe_{2}. We demonstrate that NbSe_{2} is close to a ferromagnetic instability, and analyze our results in the context of experimental measurements of the spin susceptibility in NbSe_{2}. We show how this magnetic instability, which is pronounced in a single monolayer, can enable sizable singlet-triplet mixing of the superconducting order parameter, contrary to contemporary considerations of the pairing symmetry in monolayer NbSe_{2}, and discuss approaches as to how this degree of mixing can be addressed quantitatively within our DFT framework. Our calculations also enable a quantitative description of the large anisotropy of the superconducting critical field, using DFT calculations of monolayer NbSe_{2} in the normal state.

The effects of uniaxial compressive stress on the normal state ^{17}O nuclear-magnetic-resonance properties of the unconventional superconductor Sr_{2}RuO_{4} are reported. The paramagnetic shifts of both planar and apical oxygen sites show pronounced anomalies near the nominal a-axis strain ϵ_{aa}≡ϵ_{v} that maximizes the superconducting transition temperature T_{c}. The spin susceptibility weakly increases on lowering the temperature below T≃10 K, consistent with an enhanced density of states associated with passing the Fermi energy through a van Hove singularity. Although such a Lifshitz transition occurs in the γ band formed by the Ru d_{xy} states hybridized with in-plane O p_{π} orbitals, the large Hund’s coupling renormalizes the uniform spin susceptibility, which, in turn, affects the hyperfine fields of all nuclei. We estimate this “Stoner” renormalization S by combining the data with first-principles calculations and conclude that this is an important part of the strain effect, with implications for superconductivity.

Detwinning of magnetic (nematic) domains in Fe-based superconductors has so far only been obtained through mechanical straining, which considerably perturbs the ground state of these materials. The recently discovered nonmechanical detwinning in EuFe_{2}As_{2} by ultralow magnetic fields offers an entirely different, nonperturbing way to achieve the same goal. However, this way seemed risky due to the lack of a microscopic understanding of the magnetically driven detwinning. Specifically, the following issues remained unexplained: (i) ultralow value of the first detwinning field of approximately 0.1 T, two orders of magnitude below that of BaFe_{2}As_{2}, and (ii) reversal of the preferential domain orientation at approximately 1 T and restoration of the low-field orientation above 10–15 T. In this paper, we present, using published as well as newly measured data, a full theory that quantitatively explains all the observations. The key ingredient of this theory is a biquadratic coupling between Fe and Eu spins, analogous to the Fe-Fe biquadratic coupling that drives the nematic transition in this family of materials.

We have studied the stability of RCo5-xCux (R = Y, Sm) compounds with respect to phase separation. First principles density functional calculations imply that (i) decomposition into two phases having different x is energetically favourable and (ii) both the stable x values and the Cu atomic site preferences depend on the magnetic state of the alloys. Guided by this result, we studied the structure and magnetic properties of different Sm(Co,Cu)5 and Sm(Co,Fe,Cu)5 alloys. Separation into two chemically dissimilar Sm(Co,Cu)5 phases is typical for the as-made Sm(Co,Cu)5 alloys. We also observed in different alloys a universal correlation between the room-temperature coercivity and the magnetic state at the temperature of annealing. The coercivity increases significantly if annealed 100–140°C below the Curie temperature; in particular, for SmCo2.25Fe0.75Cu2, the room-temperature coercivity increases from 12.3 to 37.3 kOe. The possibility of different magnetic state-dependent structure transformations is discussed. The experimental results do not support the spinodal decomposition theory, so we suggest that the coercivity increase might be caused by a change in preferred atomic site occupancies. [ABSTRACT FROM AUTHOR]

Essentials Strong P2Y 12 blockade may cause platelet inhibition that is only minimally enhanced by aspirin. We evaluated aspirin withdrawal on platelet reactivity in ticagrelor treated patients. Aspirin withdrawal resulted in increased platelet reactivity to arachidonic acid. Aspirin withdrawal caused little difference in adenosine diphosphate-induced platelet aggregation., Summary: Background Recent studies have shown that the thromboxane A 2 -dependent pathway is dependent on the ADP-P2Y 12 pathway, and that strong P2Y 12 receptor blockade alone causes inhibition of platelet aggregation that is minimally enhanced by aspirin. Data from the PLATO trial suggested that, among ticagrelor-treated patients, high-dose versus low-dose (< 100 mg day -1 ) aspirin is associated with an increased risk fof ischemic events. Objectives To evaluate the impact of aspirin withdrawal on platelet reactivity in acute coronary syndrome (ACS) patients treated with a potent P2Y 12 blocker. Patients/Methods This was a current prospective, randomized, placebo-controlled, double-blind, cross-over study. The study population comprised 22 consecutive ACS patients who underwent percutaneous coronary intervention and were treated with aspirin (100 mg day -1 ) and ticagrelor. Thirty days post-ACS, open-label aspirin was stopped, and patients were randomized to either blinded aspirin or placebo for 2 weeks, with each patient crossing over to the other arm for an additional 2 weeks. Platelet reactivity to arachidonic acid and ADP determined with light-transmission aggregometry (LTA) and VerifyNow was evaluated at baseline, and 2 weeks and 4 weeks later. Results Aspirin withdrawal resulted in an increase in arachidonic-acid induced platelet reactivity as determined with both LTA (77.0% ± 11.3% versus 20.8% ± 4.4%) and VerifyNow (607.7 ± 10.6 aspirin reaction units [ARU] versus 408.5 ± 14.4 ARU). Platelet response to ADP, as determined with both LTA and VerifyNow, did not differ with either aspirin or placebo (32.9% ± 2.6% versus 35.8% ± 3.6%, and 33.5 ± 6.4 P2Y 12 reaction units (PRU) versus 29.6 ± 5.7 PRU, respectively). Conclusions Aspirin withdrawal early post-ACS results in increased platelet reactivity in response to arachidonic acid, despite concomitant treatment with the potent P2Y 12 blocker ticagrelor., (© 2018 International Society on Thrombosis and Haemostasis.)

Magnetic collapse in transition metal ions is predicted from first-principles computations at pressures reached in the Earth's lower mantle and core. Magnetic collapse would lead to marked changes in geophysically important properties, such as elasticity and conductivity, and also to different geochemical behavior, such as element partitioning, than estimated by extrapolating low-pressure data, and thus change the understanding of Earth's structure and evolution. Magnetic collapse results from band widening rather than from changes in crystal field splitting under pressure. Seismic anomalies in the outer core and the lowermost mantle may be due to magnetic collapse of ferrous iron, dissolved in iron liquid in the outer core, and in solution in magnesiowustite in the lowermost mantle.