We report on the discovery of a novel triangular phase regime in system ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}$ by means electron spin resonance and magnetic susceptibility measurements. This is characterized coexistence ferromagnetic entities within globally paramagnetic far above ordering temperature. The nature this can be understood terms Griffiths singularities arising due to presence correlated quenched disorder orthorhombic phase.

This review aims to summarize more than 100 years of research on spinel compounds, mainly focusing the progress in understanding their magnetic, electronic, and polar properties during last two decades. Over years, 200 different spinels, with general formula AB2 X4, were identified or synthesized polycrystalline single-crystalline form. Many compounds are magnetic insulators semiconductors; however, a number spinel-type metals exists including superconductors some rare examples d-derived...

77Se and 87Rb nuclear magnetic resonance (NMR) experiments on Rb0.74Fe1.6Se2 reveal clearly distinct spectra originating from a majority antiferromagnetic (AF) minority metallic-superconducting (SC) phase. The very narrow NMR line of the SC phase evidences absence Fe vacancies any trace AF order. Rb content is deduced intensity measurements identifying Rb(0.3(1))Fe2Se2 as actual composition fraction. resulting estimate 0.15 electrons/Fe brings this class superconductors 245 family closer to...

We present a systematic electron-spin-resonance (ESR) study in single crystals of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{MnO}}_{3}(0<~x<~0.2).$ The temperature dependence the ESR linewidth marks all significant transitions between both orthorhombic ${(O}^{\ensuremath{'}},O)$ and rhombohedral (R) structural phases $T\ensuremath{-}x$ phase diagram. All peculiarities spectra for low x values within ${O}^{\ensuremath{'}}$ can be attributed to cooperative Jahn-Teller...

We have studied the low-energy spin-excitation spectrum of single-crystalline ${\mathrm{Rb}}_{2}{\mathrm{Fe}}_{4}{\mathrm{Se}}_{5}$ superconductor (${T}_{c}=32\text{ }\text{ }\mathrm{K}$) by means inelastic neutron scattering. In superconducting state, we observe a magnetic resonant mode centered at an energy $\ensuremath{\hbar}{\ensuremath{\omega}}_{\mathrm{res}}=14\text{ }\mathrm{meV}$ and (0.5 0.25 0.5) wave vector (unfolded Fe-sublattice notation), which differs from ones characterizing...

${}^{57}$Fe-M\"ossbauer studies of superconducting Rb${}_{0.8}$Fe${}_{1.6}$Se${}_{2.0}$ with ${T}_{C}$ $=$ 32.4 K were performed on single-crystalline and polycrystalline samples in the temperature range 4.2--295 K. They reveal presence 88% magnetic 12% nonmagnetic Fe${}^{2+}$ species same polarization dependence their hyperfine spectra. The are attributed to 16$i$ sites $\sqrt{5}\ifmmode\times\else\texttimes\fi{}\sqrt{5}\ifmmode\times\else\texttimes\fi{}1$ superstructure Fe a nanosized...

Polycrystalline samples of underdoped (Ba1- xKx)Fe2As2 (x⩽0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat 57Fe-Mößbauer spectroscopy. The structural phase transition from tetragonal to orthorhombic lattice symmetry shifts towards lower temperatures, becomes less pronounced at x=0.1–0.2 is no longer present x=0.3. Bulk superconductivity observed in all except (Ba0.9K0.1)Fe2As2 resistivity susceptibility measurements. Specific data show a...

Seeing magnetism on an atomic level Electrons tunneling from the magnetized tip of a scanning microscope into surface material can reveal material's magnetic structure. Although researchers have used technique simple nanostructures, they've had trouble preparing in just right way to visualize order more exotic materials. Enayat et al. with cluster its apex patterns ordering Fe 1+y Te, which becomes superconducting by substituting Te Se atoms. The prepared simply picking up atoms material....

The magnetic-field and temperature dependencies of the ultrasound propagation magnetization single-crystalline CoCr(2)O(4) have been studied in static pulsed magnetic fields up to 14 62 T, respectively. Distinct anomalies with significant changes sound velocity attenuation are found this spinel compound at onset long-range incommensurate-spiral-spin order T(s)=27 K transition from incommensurate commensurate states T(l)=14 K, evidencing strong spin-lattice coupling. While evolves gradually...

Abstract Magnetoelectric phenomena are intimately linked to relativistic effects and also require the material break spatial inversion symmetry time-reversal invariance. coupling can substantially affect light–matter interaction lead non-reciprocal light propagation. Here, we confirm on a fully experimental basis, without invoking either symmetry-based or material-specific assumptions, that optical magnetoelectric effect in materials with non-parallel magnetization ( M ) electric...

We report on infrared, Raman, magnetic susceptibility, and specific-heat measurements ${\text{CdCr}}_{2}{\text{O}}_{4}$ ${\text{ZnCr}}_{2}{\text{O}}_{4}$ single crystals. estimate the nearest-neighbor next-nearest-neighbor exchange constants from susceptibility extract spin-spin correlation functions obtained contribution to specific heat. By comparing with frequency shift of infrared optical phonons above ${T}_{N}$, we derive estimates for spin-phonon coupling in these systems. The...

We studied phase separation in the single-crystalline antiferromagnetic superconductor ${\mathrm{Rb}}_{2}{\mathrm{Fe}}_{4}{\mathrm{Se}}_{5}$ (RFS) using a combination of scattering-type scanning near-field optical microscopy and low-energy muon spin rotation (LE-$\ensuremath{\mu}\mathrm{SR}$). demonstrate that superconducting phases segregate into nanometer-thick layers perpendicular to iron-selenide planes, while characteristic in-plane size metallic domains reaches $10\text{ }\text{...

Inelastic neutron scattering is employed to study the reciprocal-space structure and dispersion of magnetic excitations in normal superconducting states single-crystalline Rb0.8Fe1.6Se2. We show that recently discovered resonant mode this compound has a quasi-two-dimensional character, similar overdoped iron-pnictide superconductors. Moreover, it rich in-plane dominated by four elliptical peaks, symmetrically surrounding Brillouin zone corner, without sqrt(5) x reconstruction. also present...

Using high resolution THz spectroscopy, the authors study spinon confinement in weakly coupled antiferromagnetic chain compound SrCo${}_{2}$V${}_{2}$O${}_{8}$. The confined spinons appear a hierarchy that can be fully described by one dimensional Schr\"odinger equation with linear potential.

We show that electronic Raman scattering affords a window into the essential properties of pairing potential ${V}_{\mathbf{k},{\mathbf{k}}^{\ensuremath{'}}}$ iron-based superconductors. In ${\mathrm{Ba}}_{0.6}{\mathrm{K}}_{0.4}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ we observe band dependent energy gaps along with excitonic Bardasis-Schrieffer modes characterizing, respectively, dominant and subdominant channel. The ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ symmetry all excitons allows us to identify...

We report the crystal growth and structural, magnetic, conductivity, specific heat investigations of Rb(1-x)Fe(2-y)Se2 single crystals with varying stoichiometry prepared by self-flux Bridgman methods. The system exhibits a strongly anisotropic antiferromagnetic behavior below 400 K. For 1.53 <2-y< 1.6 superconductivity is found, whereas for Fe concentrations 2-y< 1.5 2-y> insulating semiconducting observed, respectively. sharpest transition to superconducting state highest temperature T_c...

We report on spectroscopy study of elementary magnetic excitations in an Ising-like antiferromagnetic chain compound ${\mathrm{SrCo}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$ as a function temperature and applied transverse field up to 25 T. An optical well acoustic branch confined spinons, the at zero field, are identified phase below N\'eel 5 K described by one-dimensional Schr\"odinger equation. The confinement can be suppressed quantum disordered is induced 7 In this paramagnetic phase, we...

LaTiO$_3$ is known as Mott-insulator which orders antiferromagnetically at $T_{\rm N}=146$ K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with measurements the heat capacity, electrical transport measurements, optical spectroscopy in untwinned single crystals. At N}$ significant structural changes appear, are volume conserving. Concomitant anomalies also observed dc-resistivity, bulk modulus, reflectivity spectra. interpret these...

The reflectivity of single-crystalline CoO has been studied by optical spectroscopy for wave numbers ranging from 100 to $28\text{ }000\text{ }{\text{cm}}^{\ensuremath{-}1}$ and temperatures $8<T<325\text{ }\text{K}$. A splitting the cubic IR-active phonon mode on passing antiferromagnetic phase transition at ${T}_{N}=289\text{ }\text{K}$ observed. At low amounts $15.0\text{ }{\text{cm}}^{\ensuremath{-}1}$. In addition, we crystal-field ground state ${\text{Co}}^{2+}$ ions due spin-orbit...

Polarized Raman-scattering spectra of nonsuperconducting, single-crystalline FeTe are investigated as a function temperature. We have found relation between the magnitude ordered magnetic moments and linewidth ${A}_{1g}$ phonons at low temperatures. This is attributed to intermediate spin state ($S$ $=$ 1) orbital degeneracy Fe ions. Spin-phonon coupling constants been estimated based on microscopic modeling using density functional theory analysis local density. Our observations show...

We report on structural, susceptibility, conductivity and heat-capacity studies of FeSe0.5Te0.5 single crystals with 2% substitution Mn for Fe. Mn-doped samples show a higher onset temperature, narrower width the superconducting transition magnitude jump in specific heat at Tc comparison to undoped samples. The normal-state susceptibility exhibits quasi-linear increase up about 130 K. From resistivity data magnetic fields parallel c axis we derived an upper critical field Hc2 ∼ 420 kOe doped...

We report on neutron diffraction, thermal expansion, magnetostriction, dielectric and specific heat measurements polycrystalline FeCr2S4 in external magnetic fields. The ferrimagnetic ordering temperatures TC ≈ 170 K the transition at TOO 10 K, which has been associated with orbital ordering, are only weakly shifted fields up to 9 T. cubic lattice parameter is found decrease when entering state below TOO. moments of Cr- Fe-ions reduced from spin-only values throughout magnetically ordered...