Squeezing out the oddness The material Sr 2 RuO 4 has long been thought to exhibit an exotic, odd-parity kind of superconductivity, not unlike superfluidity in 3 He. How would perturbing this material's electronic structure affect its superconductivity? Steppke et al. put under large uniaxial pressure and found that critical temperature more than doubled then fell as a function strain (see Perspective by Shen). maximum roughly coincided with point at which Fermi surface underwent topological...

Hexagonal $\ensuremath{\alpha}$-Ru trichloride single crystals exhibit a strong magnetic anisotropy and we show that upon applying fields up to 14 T in the honeycomb plane successive order at ${T}_{1}=14\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ ${T}_{2}=8\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ could be completely suppressed, whereas perpendicular direction is robust. Furthermore, field dependence of $\ensuremath{\chi}(\mathrm{T})$ implies coexisting ferro- antiferromagnetic exchange between...

In the strontium iron-cobalt arsenides SrFe2-xCoxAs2 (0.2 < or = x 0.4) superconductivity with T_{c} up to 20 K is observed in magnetic susceptibility, electrical resistivity, and specific heat data. This first observation of bulk induced by electron doping this family compounds-despite strong disorder Fe-As layer-favors an itinerant electronic theory contrast strongly correlated cuprates renders a p- d-wave pairing unlikely. The ordering present SrFe2As2 rapidly suppressed substitution Fe...

Inelastic neutron scattering, susceptibility, and high-field magnetization identify LiCuVO4 as a nearest-neighbour ferromagnetic, next-nearest-neighbour frustrated, quasi–one-dimensional helimagnet, which is largely influenced by quantum fluctuations. Complementary band structure calculations provide microscopic model with the correct sign magnitude of major exchange integrals.

The layered lithium borocarbide LiBC, isovalent with and structurally similar to the superconductor MgB2, is an insulator due modulation within hexagonal layers (BC vs B2). We show that hole doping of LiBC results in Fermi surfaces B-C p sigma character couple very strongly bond stretching modes, precisely features lead superconductivity at T(c) approximately equal 40 K MgB2. Comparison Li(0.5)BC MgB2 indicates former be a prime candidate for electron-phonon coupled substantially higher...

Resistivity, specific-heat, and magnetic-susceptibility measurements performed on ${\text{SrFe}}_{2}{\text{As}}_{2}$ samples evidence a behavior very similar to that observed in LaFeAsO ${\text{BaFe}}_{2}{\text{As}}_{2}$, with the difference being formation of spin-density wave lattice deformation occur pronounced first-order transition at ${T}_{0}=205\text{ }\text{K}$. Comparing further data evidences Fe magnetism is stronger ${\text{EuFe}}_{2}{\text{As}}_{2}$ than other layered FeAs...

${\text{EuFe}}_{2}{\text{As}}_{2}$ shows a spin-density wave (SDW) type transition at 190 K and antiferromagnetic (AF) order below 20 K. Here, we have studied the effect of substitution on SDW high temperature AF Eu low temperature. 50% suppresses in turn gives rise to high-temperature superconductivity ${T}_{c}=32\text{ }\text{K}$, as observed electrical resistivity, AC susceptibility, well magnetization. A defined anomaly specific heat provides additional evidence for bulk...

From thermodynamics, local spin density approximation+Hubbard U studies and exact diagonalizations of a five-band Hubbard model on CuO2 stripes we find that Li2ZrCuO4 (Li2CuZrO4 in traditional notation) is close to ferromagnetic critical point. Analyzing its susceptibility chi(T) specific heat cp(T,H) within Heisenberg model, show the ratio 2nd 1st neighbor exchange integrals alpha=-J2/J1 approximately 0.3 value alphac=1/4. Comparing with related chain cuprates explain rather strong field...

We studied the temperature-pressure phase diagram of ${\text{EuFe}}_{2}{\text{As}}_{2}$ by electrical resistivity measurements. The spin-density-wave transition at ${T}_{0}$ associated with FeAs-layers is continuously suppressed increasing pressure, while antiferromagnetic ordering temperature ${\text{Eu}}^{2+}$ moments seems to be nearly pressure independent up 2.6 GPa. Above 2 GPa a sharp drop resistivity, $\ensuremath{\rho}(T)$, indicates onset superconductivity...

We have grown single crystals of ${\text{EuFe}}_{2}{\text{As}}_{2}$, and investigated its electrical transport thermodynamic properties. Electrical resistivity specific-heat measurements clearly establish the intrinsic nature magnetic phase transitions at 20 195 K. While high-temperature transition is associated with itinerant moment Fe, low-temperature due to order localized Eu moments. Band-structure calculations point out a very close similarity electronic structure...

We report magnetization and specific-heat measurements on polycrystalline samples of $\text{BaCdVO}{({\text{PO}}_{4})}_{2}$ show that this compound is a $S=1/2$ frustrated square lattice with ferromagnetic nearest-neighbor $({J}_{1})$ antiferromagnetic next-nearest-neighbor $({J}_{2})$ interactions. The coupling constants ${J}_{1}\ensuremath{\simeq}\ensuremath{-}3.6\text{ }\text{K}$ ${J}_{2}\ensuremath{\simeq}3.2\text{ are determined from fitting the susceptibility data confirmed by an...

The electronic structure and physical properties of the pnictide compound families REOFeAs (RE=La, Ce, Pr, Nd, Sm), AFe2As2 (A=Ca, Sr, Ba, Eu), LiFeAs FeSe are quite similar. Here, we focus on members family whose sample composition, quality single-crystal growth more controllable compared with other systems. Using first-principles band calculations, understanding relationship between crystal structure, charge doping magnetism in We will elaborate tetragonal to orthorhombic structural...

Single crystalline Sn${}_{2}$Co${}_{3}$S${}_{2}$ with the shandite-type structure was investigated by magnetization, magnetoresistance, Hall effect, and heat capacity measurements ${}^{119}$Sn M\"o\ss{}bauer spectroscopy. orders ferromagnetically at 172 K an easy-axis magnetization of $\ensuremath{\approx}$1 ${\ensuremath{\mu}}_{B}$ along hexagonal $c$ axis. The half-metallic ferromagnetic state is detailed band-structure calculations density functional theory (DFT) methods....

The natural mineral azurite Cu(3)(CO(3))(2)(OH)(2) is a frustrated magnet displaying unusual and controversially discussed magnetic behavior. Motivated by the lack of unified description for this system, we perform theoretical study based on density functional theory as well state-of-the-art numerical many-body calculations. We propose an effective generalized spin-1/2 diamond chain model which provides consistent experiments: low-temperature magnetization, inelastic neutron scattering,...

We report a systematic study of the influence antiferromagnetic and ferromagnetic phases Eu${}^{2+}$ moments on superconducting phase upon doping As site by isovalent P, which essentially acts like chemical pressure EuFe${}_{2}$As${}_{2}$. Bulk superconductivity with transition temperatures 22 28 K are observed for $x=0.16$ 0.20 samples, respectively. The Eu ions order antiferromagnetically $x$ $\ensuremath{\leqslant}0.13$, while bulk coexists Eu-antiferromagnetism 0.13 $<$ $x<0.22$. In...

Spatial inversion symmetry in crystal structures is closely related to the superconducting (SC) and magnetic properties of materials. Recently, several theoretical proposals that predict various interesting phenomena caused by breaking local have been presented. However, experimental validation has not yet progressed owing lack model Here we present evidence for antiferromagnetic (AFM) order CeRh_{2}As_{2} (SC transition temperature T_{SC}∼0.37 K), wherein Ce site breaks symmetry. The based...

Microscopic mechanisms of the puzzling insulating ferromagnetism half-filled La$_{4}$Ba$_{2}$Cu$_{2}$O$_{10}$ are elucidated with energy-resolved Wannier states. The dominant magnetic coupling, revealed through evaluated parameters ($t$, $U$, and $J$), turns out to be intersite direct exchange, a currently ignored mechanism that overwhelms antiferromagnetic superexchange. By contrast, isostructural Nd$_{4}$Ba$_{2}$Cu$_{2}$O$_{10}$ develops observed order via its characteristics 1D chain....

An unusual quasi-two-dimensional heavy band mass van Hove singularity (vHs) lies very near the Fermi energy in ${\mathrm{MgCNi}}_{3}$, recently reported to superconduct at 8.5 K. This compound is strongly exchange enhanced and unstable ferromagnetism upon hole doping with $\ensuremath{\sim}12%$ $\mathrm{Mg}\ensuremath{\rightarrow}\mathrm{Na}$ or Li (i.e., 0.04 hole/Ni). We identify an essentially infinite along $M\ensuremath{-}\ensuremath{\Gamma}$ line, which accounts for two dimensionality...

X-ray and muon spin-relaxation experiments performed on ${\text{SrFe}}_{2}{\text{As}}_{2}$ polycrystals confirm a sharp first-order transition at ${T}_{0}=205\text{ }\text{K}$ corresponding to an orthorhombic phase distortion commensurate antiferromagnetic Fe ordering with larger size of the ordered moment than reported for ${\text{BaFe}}_{2}{\text{As}}_{2}$. The structural magnetic order parameters present remarkable similarity in their temperature dependence from ${T}_{0}$ down low...

We report on {6,7}Li nuclear magnetic resonance measurements of the spin-chain compound LiCu2O2 in paramagnetic and magnetically ordered states. Below T about 24 K NMR lineshape presents a clear signature incommensurate (IC) static modulation local field consistent with an IC spiral moments. {7}Li reveals strong phason-like dynamical fluctuations extending well below K. hypothesize that series phase transitions at 24.2, 22.5, 9 reflects "Devil's staircase" type behavior generic for systems....

New germanium-platinum compounds with the filled-skutterudite crystal structure were synthesized. The and composition investigated by x-ray diffraction microprobe analysis. Magnetic susceptibility, specific heat, electrical resistivity measurements evidence superconductivity in ${\mathrm{LaPt}}_{4}{\mathrm{Ge}}_{12}$ ${\mathrm{PrPt}}_{4}{\mathrm{Ge}}_{12}$ below 8.3 K. parameters of normal superconducting states established. Strong coupling a electric field singlet ground state is found for...

Zero and longitudinal field muon spin rotation (muSR) experiments were performed on the superconductors PrPt4Ge12 LaPt4Ge12. In below Tc a spontaneous magnetization with temperature variation resembling that of superfluid density appears. This observation implies time-reversal symmetry (TRS) breaking in = 7.9 K. remarkably high for an anomalous superconductor weak gradual change related specific heat anomaly upon La substitution La_(1-x)Pr_xPt_4Ge_(12) suggests TRS is due to orbital degrees...

We have determined the physical ground state properties of compounds CeRuPO and CeOsPO by means magnetic susceptibility $\ensuremath{\chi}(T)$, specific heat $C(T)$, electrical resistivity $\ensuremath{\rho}(T)$, thermopower $S(T)$ measurements. $\ensuremath{\chi}(T)$ reveals a trivalent $4{f}^{1}$ cerium in both compounds. For pronounced decrease $\ensuremath{\rho}(T)$ below $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ indicates onset coherent Kondo scattering, which is confirmed enhanced...