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The nature of the magnetic correlations in Fe-based superconductors remains a matter of controversy. To address this issue, we use inelastic neutron scattering to characterize the strength and temperature dependence of low-energy spin…

Superconductivity · Physics 2012-03-20 Zhijun Xu , Jinsheng Wen , Guangyong Xu , Songxue Chi , Wei Ku , Genda Gu , J. M. Tranquada

We have investigated the spin fluctuations in the langasite compound Ba3NbFe3Si2O14 in both the ordered state and as a function of temperature. The low temperature magnetic structure is defined by a spiral phase characterized by magnetic…

Strongly Correlated Electrons · Physics 2015-05-19 C. Stock , L. C. Chapon , A. Schneidewind , Y. Su , P. G. Radaelli , D. F. McMorrow , A. Bombardi , N. Lee , S. -W. Cheong

Inelastic neutron scattering is used to characterize spin fluctuations in the $d$-electron heavy fermion spinel $\rm LiV_2O_4$. The spin relaxation rate, $\Gamma_Q$, for $Q=0.6$ \AA$^{-1}$ is 1.5(1) meV at low temperatures and increases…

Strongly Correlated Electrons · Physics 2009-11-07 S. -H. Lee , Y. Qiu , C. Broholm , Y. Ueda , J. J. Rush

Using a combination of single-crystal neutron scattering and reverse Monte Carlo refinements, we study the magnetic structure of paramagnetic MnO at a temperature (160\,K) substantially below the Curie-Weiss temperature…

Magnetic excitations in a Ni$_4$ magnetic molecule were investigated by inelastic neutron scattering and bulk susceptibility ($\chi_\text{bulk}$) techniques. The magnetic excitation spectrum obtained from the inelastic neutron scattering…

Strongly Correlated Electrons · Physics 2015-06-04 K. Iida , S. -H. Lee , T. Onimaru , K. Matsubayashi , T. J. Sato

We report magnetic susceptibility, specific heat and muon spin relaxation (muSR) experiments on the triangular antiferromagnet La2Ca2MnO7 which develops a genuine two-dimensional, three-sublattice \sqrt{3} \times \sqrt{3} magnetic order…

Strongly Correlated Electrons · Physics 2015-07-08 P. Dalmas de Réotier , C. Marin , A. Yaouanc , T. Douce , A. Sikora , A. Amato , C. Baines

The high-temperature ferromagnet MnBi continues to receive attention as a candidate to replace rare-earth-containing permanent magnets in applications above room temperature. This is due to a high Curie temperature, large magnetic moments,…

Strongly Correlated Electrons · Physics 2016-05-12 T. J. Williams , A. E. Taylor , A. D. Christianson , S. E. Hahn , R. S. Fishman , D. S. Parker , M. A. McGuire , B. C. Sales , M. D. Lumsden

We present a theory of out-of-equilibrium ultrafast spin dynamics in magnetic heterostructures based on the s-d model of ferromagnetism. Both in the bulk and across interfaces, the exchange processes between the itinerant s and the…

Mesoscale and Nanoscale Physics · Physics 2015-12-02 Erlend G. Tveten , Arne Brataas , Yaroslav Tserkovnyak

The spectrum of spin fluctuations in the stacked-triangular antiferromagnet YMnO3 was studied above the Neel temperature using both unpolarized and polarized inelastic neutron scattering. We find an in-plane and an out-of-plane excitation.…

Strongly Correlated Electrons · Physics 2009-11-11 B. Roessli , S. N. Gvasaliya , E. Pomjakushina , K. Conder

Spin correlations in the paramagnetic phase of lanthanum cuprate have been studied using polarized neutron scattering, with two important results. First, the temperature dependence of the characteristic energy scale of the fluctuations and…

Strongly Correlated Electrons · Physics 2009-11-11 A. M. Toader , J. P. Goff , M. Roger , N. Shannon , J. R. Stewart , M. Enderle

In the local or itinerant extreme, magnetic excitations can be described by the Heisenberg model which treats electron spins as localized moments, or by the itinerant-electron model where the exchange interaction between electrons leads to…

Spin correlations in the pyrochlore antiferromagnet Y_2Ru_2O_7 with Curie-Weiss temperature $\Theta_{CW}=-1100$ K and critical temperature T_N=77 K were examined through neutron scattering. For $T_N<T<\Theta_{CW}/3$ the data show spin…

Strongly Correlated Electrons · Physics 2014-07-03 J. van Duijn , N. Hur , J. W. Taylor , Y. Qiu , Q. Z. Huang , S. -W. Cheong , C. Broholm , T. G. Perring

We report inelastic neutron scattering measurements performed on a single crystal of the heavy fermion compound Ce$_{0.925}$La$_{0.075}$Ru$_{2}$Si$_{2}$, which is at the borderline between an antiferromagnetically ordered and a paramagnetic…

Strongly Correlated Electrons · Physics 2007-05-23 W. Knafo , S. Raymond , B. Fåk , M. A. Adams , P. Lejay , J. Flouquet

After several decades of studies of high-temperature superconductivity, there is no compelling theory for the mechanism yet; however, the spin fluctuations have been widely believed to play a crucial role in forming the superconducting…

We report the NQR study on the pressure-induced paramagnetic state in the antiferromagnetic (AF) intermetallic compound YMn$_2$ with the N\'eel temperature T_N=100 K at ambient pressure. From the $T$ variation of the nuclear spin-lattice…

Strongly Correlated Electrons · Physics 2007-05-23 K. Nishikido , C. Thessieu , G-q. Zheng , Y. Kitaoka , K. Asayama , R. Hauser

Muon spin rotation (muSR) experiments reveal unconventional spin freezing and dynamics in the two-dimensional (2D) triangular lattice antiferromagnet NiGa2S4. Long-lived disordered Ni-spin freezing (correlation time > 10-6 s at 2 K) sets in…

Strongly Correlated Electrons · Physics 2009-11-13 D. E. MacLaughlin , Y. Nambu , S. Nakatsuji , R. H. Heffner , Lei Shu , O. O. Bernal , K. Ishida

Spin excitations are one of the top candidates for mediating electron pairing in unconventional superconductors. Their coupling to superconductivity is evident in a large number of systems, by the observation of an abrupt redistribution of…

Neutron scattering experiments on a polycrystalline sample of the frustrated pyrochlore magnet Tb2Ti2O7, which does not show any magnetic order down to 50 mK, have revealed that it shows condensation behavior below 0.4 K from a thermally…

Disordered Systems and Neural Networks · Physics 2011-12-13 Hiroshi Takatsu , Hiroaki Kadowaki , Taku J. Sato , Jeffrey W. Lynn , Yoshikazu Tabata , Teruo Yamazaki , Kazuyuki Matsuhira

To understand spin interactions in materials of the Cu$_2$Sb structure type, inelastic neutron scattering of Fe$_2$As single crystals was examined at different temperatures and incident neutron energies. The experimental phonon spectra…

^{139}La NMR measurements of La_{2/3}Ca_{1/3}MnO_3 performed in the paramagnetic state and high magnetic fields are reported. Analysis of the high temperature spectrum measured establishes that the spectrum it is a standard powder pattern…

Strongly Correlated Electrons · Physics 2009-10-31 K. E. Sakaie , C. P. Slichter , P. Lin , M. Jaime , M. B. Salamon