Electron spin resonance of Eu2+ in the Eu doped clathrate Ba6Ge25

We report electron spin resonance (ESR) investigations of the clathrate compound Ba6-xEuxGe25 (x=0.03-0.4) which exhibits a temperature induced, two-step reconstructive structure transformation at temperatures between 185 K and 223 K. The linewidth of the Eu2+ ESR proves to be sensitive to the transformation. Another anomaly in the temperature dependence of the linewidth is found near T=60 K which points towards another possible structural transition. Both anomalies seen in the ESR linewidth are not sensitive to the Eu content in contrast to the strong Eu-concentration dependence of transport properties. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2005

Crystal Field and Dzyaloshinsky-Moriya Interaction in orbitally ordered La_{0.95}Sr_{0.05}MnO_3: An ESR Study

We present a comprehensive analysis of Dzyaloshinsky-Moriya interaction and crystal-field parameters using the angular dependence of the paramagnetic resonance shift and linewidth in single crystals of La_{0.95}Sr_{0.05}MnO_3 within the orthorhombic Jahn-Teller distorted phase. The Dzyaloshinsky-Moriya interaction (~ 1K) results from the tilting of the MnO_6 octahedra against each other. The crystal-field parameters D and E are found to be of comparable magnitude (~ 1K) with D ~= -E. This indicates a strong mixing of the |3z^2-r^2> and |x^2-y^2> states for the real orbital configuration.Comment: 12 pages, 6 figure

The Orbital Order Parameter in La0.95Sr0.05MnO3 probed by Electron Spin Resonance

The temperature dependence of the electron-spin resonance linewidth in La0.95Sr0.05MnO3 has been determined and analyzed in the paramagnetic regime across the orbital ordering transition. From the temperature dependence and the anisotropy of linewidth and $g$-value the orbital order can be unambiguously determined via the mixing angle of the wave functions of the $e_{\rm g}$-doublet. The linewidth shows a similar evolution with temperature as resonant x-ray scattering results

Observation of a Griffiths phase in paramagnetic La1-xSrxMnO3

We report on the discovery of a novel triangular phase regime in the system La1-xSrxMnO3 by means of electron spin resonance and magnetic susceptibility measurements. This phase is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase far above the magnetic ordering temperature. The nature of this phase can be understood in terms of Griffiths singularities arising due to the presence of correlated quenched disorder in the orthorhombic phase

Interplay of superexchange and orbital degeneracy in Cr-doped LaMnO3

We report on structural, magnetic and Electron Spin Resonance (ESR) investigations in the manganite system LaMn_{1-x}Cr_{x}O_{3} (x<=0.5). Upon Cr-doping we observe a reduction of the Jahn-Teller distortion yielding less distorted orthorhombic structures. A transition from the Jahn-Teller distorted O' to the pseudocubic O phase occurs between 0.3<x<0.4. A clear connection between this transition and the doping dependence of the magnetic and ESR properties has been observed. The effective moments determined by ESR seem reduced with respect to the spin-only value of both Mn^{3+} and Cr^{3+} ions

Visualizing high-temperature spin dynamics in La1-xCaxMnO3 from a mapping of EPR linewidth and g factor

This paper presents an analysis of electron paramagnetic resonance parameters, i.e., g factor, linewidth, and intensity on powder samples of La1-xCaxMnO3 at the commensurate carrier concentrations of x = N/8 (N = 1, 2, 3, 4, 5, 6, and 7). We demonstrate that the mapping of EPR parameters offers a powerful tool to investigate high-temperature spin dynamics in the phase diagram of colossal magnetoresistance (CMR) manganites. Our results convince that the spin-spin relaxation mechanism should dominate the high-temperature paramagnetic regime in CMR manganites.Comment: 19 pages, 6 figure

Observation of a griffiths phase in paramagnetic La1-xSrxMnO3

We report on the discovery of a novel triangular phase regime in the system La1-xSrxMnO3 by means of electron spin resonance and magnetic susceptibility measurements. This phase is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase far above the magnetic ordering temperature. The nature of this phase can be understood in terms of Griffiths singularities arising due to the presence of correlated quenched disorder in the orthorhombic phase. © 2005 The American Physical Society

Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target

Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured in bins of the Bjorken scaling variable $x$, the relative virtual-photon energy $y$ and the relative hadron energy $z$. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target ($^6$LiD). They cover the kinematic domain in the photon virtuality $Q^2$ > 1(GeV/c$)^2$, $0.004 < x < 0.4$, $0.2 < z < 0.85$ and $0.1 < y < 0.7$. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions

The Polarised Valence Quark Distribution from semi-inclusive DIS

The semi-inclusive difference asymmetry A^{h^{+}-h^{-}} for hadrons of opposite charge has been measured by the COMPASS experiment at CERN. The data were collected in the years 2002-2004 using a 160 GeV polarised muon beam scattered off a large polarised ^6LiD target and cover the range 0.006 < x < 0.7 and 1 < Q^2 < 100 (GeV/c)^2. In leading order QCD (LO) the asymmetry A_d^{h^{+}-h^{-}} measures the valence quark polarisation and provides an evaluation of the first moment of Delta u_v + Delta d_v which is found to be equal to 0.40 +- 0.07 (stat.) +- 0.05 (syst.) over the measured range of x at Q^2 = 10 (GeV/c)^2. When combined with the first moment of g_1^d previously measured on the same data, this result favours a non-symmetric polarisation of light quarks Delta u-bar = - Delta d-bar at a confidence level of two standard deviations, in contrast to the often assumed symmetric scenario Delta u-bar = Delta d-bar = Delta s-bar = Delta s.Comment: 7 pages, 3 figures, COMPASS, revised: details added, author list update