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[en] Magnetization and susceptibility studies on single crystals of the pyrochlore Ho2Ti2O7 are reported. Magnetization isotherms are shown to be qualitatively similar to that predicted by the nearest-neighbor spin-ice model. Below the lock-in temperature, T*≅1.97 K, magnetization is consistent with the locking of spins along  directions in a specific two-spins-in, two-spins-out arrangement. Below T* the magnetization for B|| displays a two step behavior signaling the breaking of the ice rules
[en] We have performed neutron scattering and a.c. susceptibility χa.c. studies on polycrystallline Tb2Ti2O7 to investigate the magnetic correlations in this antiferromagnetic pyrochlores. Evidence of changes in the magnetic correlation length has been observed by neutron diffraction in different parts of an applied field/temperature phase diagram. This cooperative paramagnet has been shown to increase its magnetic correlations, from nearest neighbour to ∼100 A, in modest fields (<7 T) and temperatures (T>2 K); however, in zero field the system does not order above 15 mK, even with its large moment
[en] The high flux and low background of the new backscattering spectrometer at the SNS combine to produce an excellent signal to noise ratio, allowing us to investigate a low lying weak excitation never seen before in the spin ice, Ho2Ti2O7. This non-dispersive excitation has been observed at E = 26.3 μeV below 100 K but is resolution limited only below ∼ 65 K. It is indifferent to magnetic fields below μ0H = 4.5 T, at 1.6 K. These characteristics help us to identify the excitation as due to the nuclear spin system.
[en] A continuum of magnetic states has been observed by neutron scattering from the spin-1 chain compound CsNiCl3 in its disordered gapped one-dimensional phase. Results using both triple-axis and time-of-flight spectrometers show that around the antiferromagnetic point Qc=π , the continuum lies higher in energy than the Haldane gapped excitations. At 6 K the integrated intensity of the continuum is about 12(2)% of the total spectral weight. This result is considerably larger than the 1% - 3% weight predicted by the nonlinear sigma model for the three-particle continuum
[en] In this paper we review the neutron scattering work performed on 3 different antiferromagnetic pyrochlores which reveal how the character of the magnetic interactions plays a major role on the eventual outcome of the magnetic ground state. Tb2Ti2O7, Er2Ti2O7 and Y2Mo2O7 have all been extensively studied over the past 15 years and are known to display, respectively, spin liquid, long range ordered and glassy ground states. Although detailed experiments have been performed on these compounds, and much is known about their low temperature properties, a detailed theoretical understanding of their ground states remains elusive
[en] The magnetic pyrochlore Er2Ru2O7 has been studied with neutron scattering and susceptibility measurements down to a base temperature of 270 mK. For the low temperature phase in which the Er sublattice orders, new magnetic Bragg peaks are reported which can be indexed with integer (hkl) for a face centered cubic cell. Inelastic measurements reveal a wealth of crystal field levels of the Er ion and a copious amount of magnetic scattering below 15 meV. The three lowest groups of crystal field levels are at 6.7, 9.1 and 18.5 meV.
[en] Measurements of the magnetic susceptibility of the frustrated pyrochlore magnet Gd2Sn2O7 have been performed at temperatures below T = 5 K and in magnetic fields up to H = 12 T. The phase boundaries determined from these measurements are mapped out in an H-T phase diagram. In this gadolinium compound, where the crystal-field splitting is small and the exchange and dipolar energy are comparable, the Zeeman energy overcomes these competing energies, resulting in at least four magnetic phase transitions below 1 K. These data are compared against those for Gd2Ti2O7 and will, we hope, stimulate further studies.
[en] The pyrochlore material Ho2Ti 2O7 has been suggested to show ''spin ice'' behavior. We present neutron scattering and specific heat results that establish unambiguously that Ho2Ti 2O7 exhibits spin ice correlations at low temperature. Diffuse magnetic neutron scattering is quite well described by a nearest neighbor spin ice model and very accurately described by a dipolar spin ice model. The heat capacity is well accounted for by the sum of a dipolar spin ice contribution and an expected nuclear spin contribution, known to exist in other Ho3+ salts. These results settle the question of the nature of the low temperature spin correlations in Ho2Ti 2O7 for which contradictory claims have been made
[en] The 8th International Conference on Highly Frustrated Magnetism 2016 (HFM 2016) took place between the 7th and 11th of September 2016 at the GIS Convention Center at National Taiwan University, Taipei, Taiwan. Over 260 participants from all over the world, attended the meeting making it the largest HFM to-date and revealing the impressive growth in the community since the original meeting in Waterloo, Canada where 80 participants attended. Preceding the meeting a school was held at the National Synchrotron Radiation Research Center to help those new to the field understand the material they were likely to see at HFM2016. Our thanks to the international speakers who attended this school John Chalker, Michel Kenzelmann, Philippe Mendels, Luigi Paolasini, Kirrily Rule, Yixi Su, Isao Watanabe and those from Taiwan W. T. Chen, Y-J, Kao, L. J. Chang and C. S. Ku, for their enlightening presentations.The HFM 2016 conference consisted of five plenary talks by H Takagi, B D Gaulin, L Balents, Y Tokura and S T Bramwell, 20 invited and 40 contributed presentations, and about 160 poster presentations from all aspects of theoretical and experimental frustrated magnetism. During the conference period, many stimulating discussions were held both inside and outside the conference room. Excursions to Taipei 101 and the National Palace Museum, as well as several organized dinners and receptions allowed the participants to initiate collaborations and discuss the hottest issues. The subjects covered in the conference included:· Quantum frustrated magnetism and spin liquids· Novel ordering of geometrically frustrated magnets· Frustration effect on the coupling to lattice, orbital and charge degrees of freedom· Exotic phenomena induced by macroscopic degeneracy· Field effect on frustrated magnetism etc.These proceeding represent a very small, but valuable contribution to the community. I hope you enjoy reading them. In view of the rapid growth of the field, it has been decided at the conference that the next HFM conference will be held in two years, in 2018, on the campus of UC Davis, followed one in Shanghai around December 2019.Finally, on behalf of the HFM 2016 Organizing Committee, I wish to deeply thank all the people who generously helped us in organizing and running the HFM 2016 conference. These include the numerous funding sources, Committee Members, Program and Session chairs, Chia-Chi Liu, Chao-Jung Kuo, Hanz Peng, Laura Bravo and Stella Su and of course all the participants, without you it would have simply been another wet week in Taipei.One might remember HFM2016 for the power outage, but we hope you remember the taste, sounds and views of Taipei as well as stimulation conversations and hopefully the beginnings of productive partnerships. (paper)
[en] The new pyrochlore Mn2Sb2O7 has been synthesized via a low-temperature method to retain cubic Fd3-barm symmetry. The resulting material has an unconventional spin glass state at TSG∼41 K, in the absence of detectable site disorder or a structural phase transition. A peak in the DC susceptibility at TSG, and a characteristic shift in the real part of the AC susceptibility was noted, but with a slightly more dynamic state than predicted through the typical Mydosh spin glass parameter of ΔTSG/[TSGlog(ω)]. Time-dependent magnetization measurements show glassy behavior below 41 K. Elastic neutron scattering measurements on powder samples show significant magnetic diffuse scattering from the Mn spins beneath the transition, similar to the scattering observed in the spin liquid Tb2Ti2O7. The dynamic character of Mn2Sb2O7 is inferred to arise from the frustration inherent within the pyrochlore lattice