Related papers: Direct observation of electric-quadrupolar order i…
We have used element specific X-ray resonant scattering to investigate the M edge resonances in a single crystal of \unpo. Earlier neutron diffraction and M\"{o}ssbauer studies had shown the presence of long-range AF order below T$_{N}$ =…
An antiferro ordering of an electric hexadecapole moment is discussed as a promising candidate for the long standing mystery of the hidden order phase in URu$_{2}$Si$_{2}$. Based on localized $f$-electron picture, we discuss the rationale…
We report the results of resonant X-ray scattering experiments performed at the Np M_4,5 edges in NpO_2. Below T_0 = 25 K, the development of long-range order of Np electric quadrupoles is revealed by the growth of superlattice Bragg peaks.…
Resonant x-ray diffraction performed at the $\rm L_{II}$ and $\rm L_{III}$ absorption edges of Ru has been used to investigate the magnetic and orbital ordering in Ca$_2$RuO$_4$ single crystals. A large resonant enhancement due to electric…
Neutron scattering experiments have revealed a field-induced antiferroquadrupolar order parameter in the Pr-based heavy-fermion superconductor PrOs$_4$Sb$_{12}$. We observed the field-induced antiferromagnetic dipole moment with the…
Resonant elastic X-ray scattering is a powerful technique for measuring multipolar order parameters. In this paper, we theoretically and experimentally study the possibility of using this technique to detect the proposed multipolar order…
Based on a localized crystal electric field model for the U^{4+} in the (5f)^2-configuration, we analyze the resonant x-ray scattering spectra around U M_{IV} and M_{V} edges in URu_{2}Si_{2}, taking full Coulomb and spin-orbit interactions…
Antiferroquadrupolar (AFQ) ordering has been conjectured in several rare-earth compounds to explain their anomalous magnetic properties. No direct evidences for AFQ ordering, however, have been reported. Using the resonant x-ray scattering…
We investigate antiferro quadrupole orders in systems with non-Kramers doublet ground state with total angular momentum J=4 in T_d point group symmetry. We demonstrate that a pure O_2^2 antiferro quadrupole order is impossible in general…
The origin of non-collinear magnetic order in UO$_{2}$ is studied by an ab initio dynamical-mean-field-theory framework in conjunction with a linear-response approach for evaluating inter-site superexchange interactions between U 5$f^{2}$…
X-ray resonant scattering at the K-edge of transition metal oxides is shown to measure the orbital order parameter, supposed to accompany magnetic ordering in some cases. Virtual transitions to the 3d-orbitals are quadrupolar in general. In…
We provide a first-principle, materials-specific theory of multipolar order and superexchange in NpO$_2$ by means of a non-collinear local-density approximation +$U$ (LDA+$U$) method. Our calculations offer a precise microscopic description…
The recent experimental finding of large-amplitude antiferromagnetism induced by uniaxial strain shows that the "hidden" low-field order of URu2Si2 breaks time reversal invariance. We propose a new crystal field model which supports…
Based on Monte Carlo calculations, multipolar ordering on the Penrose tiling, relevant for two-dimensional molecular adsorbates on quasicrystalline surfaces and for nanomagnetic arrays, has been analyzed. These initial investigations are…
We discuss possible approaches to the problem of the URu2Si2 "Hidden Order" (HO) which remains unsolved after tremendous efforts of researches. Suppose there is no spatial symmetry breaking at the HO transition temperature and solely the…
Under zero magnetic field, a quadrupolar order parameter at q_Q=(1/2,1/2,1/2) in a typical antiferro-quadrupole (AFQ) ordering compound CeB6 has been observed for the first time by means of a resonant X-ray scattering (RXS) te\ chnique. The…
A systematic search for possible order parameters of the so-called hidden order of URu$_{2}$Si$_{2}$ is conducted. Among the possible candidates that do fulfill the experimental symmetry restrictions on the hidden order parameter, we find…
Using Raman and infrared spectroscopies the spontaneous ferriquadrupolar ordering has been observed in the rare-earth-based system KDy(MoO$_4$)$_2$. Ordered quadrupoles in the electron subsystem attend non-equivalent distortions of…
The invariant form of the hyperfine interaction between multipolar moments and the nuclear spin is derived, and applied to discuss possibilities to identify the antiferro-octupolar (AFO) moments by NMR experiments. The ordered phase of…
We report the first direct resonant soft x-ray scattering observations of orbital ordering. We have studied the low temperature phase of La$_{0.5}$Sr$_{1.5}$MnO$_4$, a compound that displays charge and orbital ordering. Previous claims of…