57 research outputs found

    Magnetic chirality as probed by neutron scattering

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    We review the concept of chirality, at first briefly in a general context then in the specific framework of the spin networks. We next discuss to what extent neutron scattering appears as an unconvertible tool to probe magnetic chirality in the static and dynamical regimes of the spins. The remarkable chiral ground state and excitations of the Fe-langasite compound finally serves to illustrate the use of neutron polarimetry in the experimental studies of the magnetic chirality.Comment: 32 page

    Structural and magnetic properties in the ruthenate Bi2.67Pr0.33Ru3O11

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    An unreported praseodymium substituted phase of the Bi-Ru-O system with formula Bi2.67Pr0.33Ru3O11was prepared. Its crystal structure and magnetic properties were investigated. Pr substituted occurs only on one of the two Bi sites. The magnetism of the compound is essentially dominated by a Pr3+ contribution. A non linear variation of the reciprocal magnetic susceptibility is observed that appears to account for crystal electric field interactions on the Pr3+ ions

    Spin liquid correlations in Nd-langasite anisotropic Kagom\'e antiferromagnet

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    Dynamical magnetic correlations in the geometrically frustrated Nd_3\_3Ga_5\_5SiO_14\_{14} compound were probed by inelastic neutron scattering on a single crystal. A scattering signal with a ring shape distribution in reciprocal space and unprecedented dispersive features was discovered. Comparison with calculated static magnetic scattering from models of correlated spins suggests that the observed phase is a spin liquid inherent to an antiferromagnetic kagom\'e-like lattice of anisotropic Nd moments.Comment: 4 page

    Structural and magnetic properties of the (Bi2-xPrx)Ru2O7 pyrochlore solid solution (0 <= x <= 2)

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    We report a detailed study of structural and magnetic properties of the pyrochlore-type (Bi2-xPrx)Ru2O7 series. Eleven compositions with 0 <= x <= 2 were prepared by solid state reaction at 1050 degrees C and found to form a solid solution in the whole range of compositions. Structural refinements from X-ray powder diffraction data by the Rietveld method show that the main variation concerns the ruthenium site. Ru-O distances increase and the Ru-O-Ru angle (bridging corner-sharing Ru-O octahedra) decreases with increasing praseodymium content, in agreement with the metal-semiconductor transition observed previously in this system. Magnetic measurements show that the metallic Pauli paramagnetism of Ru in Bi2Ru2O7 evolves to a magnetism of localized low spin moments coexisting with the magnetism of Pr3+ cations moments. Strong magnetic correlations are present at high Pr content, as illustrated by a N\'eel temperature of -224 K for Pr2Ru2O7. However no evidence of a magnetic ordering was found, suggesting that the end compound Pr2Ru2O7 of the series might stabilize a spin liquid phase

    Magnetic order in the frustrated Ising-like chain compound Sr3_3NiIrO6_6

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    We have studied the field and temperature dependence of the magnetization of single crystals of Sr3NiIrO6. These measurements evidence the presence of an easy axis of anisotropy and two anomalies in the magnetic susceptibility. Neutron powder diffraction realized on a polycrystalline sample reveals the emergence of magnetic reflections below 75 K with magnetic propagation vector k ~ (0, 0, 1), undetected in previous neutron studies [T.N. Nguyen and H.-C zur Loye, J. Solid State Chem., 117, 300 (1995)]. The nature of the magnetic ground state, and the presence of two anomalies common to this family of material, are discussed on the basis of the results obtained by neutron diffraction, magnetization measurements, and symmetry arguments

    Parity Broken Chiral Spin Dynamics in Ba3_3NbFe3_3Si2_2O14_{14}

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    The spin wave excitations emerging from the chiral helically modulated 120∘^{\circ} magnetic order in a langasite Ba3_3NbFe3_3Si2_2O14_{14} enantiopure crystal were investigated by unpolarized and polarized inelastic neutron scattering. A dynamical fingerprint of the chiral ground state is obtained, singularized by (i) spectral weight asymmetries answerable to the structural chirality and (ii) a full chirality of the spin correlations observed over the whole energy spectrum. The intrinsic chiral nature of the spin waves elementary excitations is shown in absence of macroscopic time reversal symmetry breaking

    THz Magneto-electric atomic rotations in the chiral compound Ba3_3NbFe3_3Si2_2O14_{14}

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    We have determined the terahertz spectrum of the chiral langasite Ba3_3NbFe3_3Si2_2O14_{14} by means of synchrotron-radiation measurements. Two excitations are revealed that are shown to have a different nature. The first one, purely magnetic, is observed at low temperature in the magnetically ordered phase and is assigned to a magnon. The second one persits far into the paramagnetic phase and exhibits both an electric and a magnetic activity at slightly different energies. This magnetoelectric excitation is interpreted in terms of atomic rotations and requires a helical electric polarization

    First results from the OSQAR photon regeneration experiment: No light shining through a wall

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    A new method to amplify the photon-axion conversions in magnetic field is proposed using a buffer gas at a specific pressure. As a first result, new bounds for mass and coupling constant for purely laboratory experiments aiming to detect any hypothetical scalars and pseudo-scalars which can couple to photons were obtained at 95% confidence level, excluding the PVLAS result newly disclaimed.Comment: 4 pages, 5 figure

    Vibronic collapse of ordered quadrupolar ice in the pyrochore magnet Tb2+x_{2+x}Ti2−x_{2-x}O7+y_{7+y}

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    While the spin liquid state in the frustrated pyrochlore Tb2+x_{2+x}Ti2−x_{2-x}O7+y_{7+y} has been studied both experimentally and theoretically for more than two decades, no definite description of this unconventional state has been achieved. Using synchrotron based THz spectroscopy in combination with quantum numerical simulations, we highlight a significant link between two previously unrelated features: the existence of a quadrupolar order following an ice rule and the presence of strong magneto-elastic coupling in the form of hybridized Tb3+^{3+} crystal-field and phonon modes. The magnitude of this so-called vibronic process, which involves quadrupolar degrees of freedom, is significantly dependent on small off-stoichiometry xx and favors all-in all-out like correlations between quadrupoles. This mechanism competes with the long range ordered quadrupolar ice, and for slightly different stoichiometry, is able to destabilize it.Comment: Main text: 7 pages, 3 figures ; Supplemental Material: 6 pages, 2 figure
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