Paramagnon dispersion in beta-FeSe observed by Fe L-edge resonant inelastic x-ray scattering

PHYSICAL REVIEW B 99 (2019) ARTN 014505

MC Rahn, K Kummer, NB Brookes, AA Haghighirad, K Gilmore, AT Boothroyd

Spin-charge-lattice coupling in quasi-one-dimensional Ising spin chain CoNb2O6.

Journal of physics. Condensed matter : an Institute of Physics journal 31 (2019) 195802-

M Nandi, D Prabhakaran, P Mandal

Magnetization, magnetostriction and dielectric constant measurements are performed on single crystals of quasi-one-dimensional Ising spin chain CoNb2O6 at temperatures below and above the antiferromagnetic phase transition. Field-induced magnetic transitions are clearly reflected in magnetodielectric and magnetostriction data. Sharp anomalies are observed around the critical fields of antiferromagnetic to ferrimagnetic and ferrimagnetic to saturated-paramagnetic transition in both magnetodielectric and magnetostriction experiments. Detailed analysis of temperature and field dependence of dielectric constant and magnetostriction suggests that spins are coupled with lattice as well as charges in CoNb2O6. Below the antiferromagnetic transition temperature, the overall resemblance in anomalies, observed in various physical parameters such as magnetization, dielectric constant, magnetostriction and magnetic entropy change gives a deeper insight about the influence of spin configuration on these parameters in CoNb2O6.

Transverse and longitudinal spin-fluctuations in INVAR Fe0.65Ni0.35.

Journal of physics. Condensed matter : an Institute of Physics journal 31 (2019) 025802-

JR Stewart, SR Giblin, D Honecker, P Fouquet, D Prabhakaran, JW Taylor

The presence of spin-fluctuations deep within the ordered state of ferromagnetic [Formula: see text] alloy [Formula: see text] has long been suspected but seldom directly observed. Inhomogeneities of one type or another have been cited as important in stabilizing [Formula: see text] behaviour-either longitudinal spin-fluctuations associated with the [Formula: see text]-state (local environment) model or transverse magnetisation arising from non-collinear spin structures. In this study we employ small-angle neutron scattering with neutron polarization analysis to distinguish between the two possibilities. Surprisingly we in fact find evidence of dominant but uncorrelated longitudinal spin-fluctuations coexisting with transverse magnetisation which exists in short-range clusters of size ~[Formula: see text]. This finding supports recent first principles calculations of [Formula: see text] in which both longitudinal spin-fluctuations and magnetic short-range order are identified as important ingredients in reproducing the equilibrium [Formula: see text] lattice.

Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO3

PHYSICAL REVIEW B 97 (2018) ARTN 134304

SL Holm, A Kreisel, TK Schaeffer, A Bakke, M Bertelsen, UB Hansen, M Retuerto, J Larsen, D Prabhakaran, PP Deen, Z Yamani, JO Birk, U Stuhr, C Niedermayer, AL Fennell, BM Andersen, K Lefmann

Static and Fluctuating Magnetic Moments in the Ferroelectric Metal LiOsO3

Proceedings of the 14th International Conference on Muon Spin Rotation, Relaxation and Resonance (μSR2017) Journal of the Physical Society of Japan (2018)

FKK Kirschner, F Lang, FL Pratt, T Lancaster, Y Shi, Y Guo, AT Boothroyd, SJ Blundell

Stability of charge-stripe ordered La2-xSrxNiO4+delta at one third doping


PG Freeman, RA Mole, NB Christensen, A Stunault, D Prabhakaran

Magnetic and electronic structure of the layered rare-earth pnictide EuCd2Sb2

PHYSICAL REVIEW B 98 (2018) ARTN 064419

J-R Soh, C Donnerer, KM Hughes, E Schierle, E Weschke, D Prabhakaran, AT Boothroyd

Coupling between Spin and Charge Order Driven by Magnetic Field in Triangular Ising System LuFe2O4+delta

CRYSTALS 8 (2018) ARTN 88

L Ding, F Orlandi, DD Khalyavin, AT Boothroyd, D Prabhakaran, G Balakrishnan, P Manuel

Investigation of a Spin Transition in a LaCoO3 Single Crystal by the Method of X-Ray Magnetic Circular Dichroism at the Cobalt K- and L (2,3)-Edges

PHYSICS OF THE SOLID STATE 60 (2018) 288-291

VV Sikolenko, IO Troyanchuk, DV Karpinsky, A Rogalev, F Wilhelm, R Rosenberg, D Prabhakaran, EA Efimova, VV Efimov, SI Tiutiunnikov, IA Bobrikov

Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO3 (vol 97, 134304, 2018)

PHYSICAL REVIEW B 98 (2018) ARTN 099902

S Holm-Dahlin, A Kreisel, TK Schaffer, A Bakke, M Bertelsen, UB Hansen, M Retuerto, J Larsen, D Prabhakaran, PP Deen, Z Yamani, JO Birk, U Stuhr, C Niedermayer, AL Fennell, BM Andersen, K Lefmann

Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd2As2

PHYSICAL REVIEW B 97 (2018) ARTN 214422

MC Rahn, J-R Soh, S Francoual, LSI Veiga, J Strempfer, J Mardegan, DY Yan, YF Guo, YG Shi, AT Boothroyd

Persistence of antiferromagnetic order upon La substitution in the 4d(4) Mott insulator Ca2RuO4

PHYSICAL REVIEW B 98 (2018) ARTN 014429

D Pincini, S Boseggia, R Perry, MJ Gutmann, S Ricco, LSI Veiga, CD Dashwood, SP Collins, G Nisbet, A Bombardi, DG Porter, F Baumberger, AT Boothroyd, DF McMorrow

Tracking a hysteretic and disorder-broadened phase transition via the electromagnon response in improper ferroelectrics


CDW Mosley, D Prabhakaran, J Lloyd-Hughes

Spin dynamics and exchange interactions in CuO measured by neutron scattering

PHYSICAL REVIEW B 97 (2018) ARTN 144401

H Jacobsen, SM Gaw, AJ Princep, E Hamilton, S Toth, RA Ewings, M Enderle, EMH Wheeler, D Prabhakaran, AT Boothroyd

Pauling Entropy, Metastability, and Equilibrium in Dy_{2}Ti_{2}O_{7} Spin Ice.

Physical review letters 121 (2018) 067202-

SR Giblin, M Twengström, L Bovo, M Ruminy, M Bartkowiak, P Manuel, JC Andresen, D Prabhakaran, G Balakrishnan, E Pomjakushina, C Paulsen, E Lhotel, L Keller, M Frontzek, SC Capelli, O Zaharko, PA McClarty, ST Bramwell, P Henelius, T Fennell

Determining the fate of the Pauling entropy in the classical spin ice material Dy_{2}Ti_{2}O_{7} with respect to the third law of thermodynamics has become an important test case for understanding the existence and stability of ice-rule states in general. The standard model of spin ice-the dipolar spin ice model-predicts an ordering transition at T≈0.15  K, but recent experiments by Pomaranski et al. suggest an entropy recovery over long timescales at temperatures as high as 0.5 K, much too high to be compatible with the theory. Using neutron scattering and specific heat measurements at low temperatures and with long timescales (0.35  K/10^{6}  s and 0.5  K/10^{5}  s, respectively) on several isotopically enriched samples, we find no evidence of a reduction of ice-rule correlations or spin entropy. High-resolution simulations of the neutron structure factor show that the spin correlations remain well described by the dipolar spin ice model at all temperatures. Furthermore, by careful consideration of hyperfine contributions, we conclude that the original entropy measurements of Ramirez et al. are, after all, essentially correct: The short-time relaxation method used in that study gives a reasonably accurate estimate of the equilibrium spin ice entropy due to a cancellation of contributions.

Folded superstructure and degeneracy-enhanced band gap in the weak-coupling charge density wave system 2H-TaSe2

PHYSICAL REVIEW B 97 (2018) ARTN 115118

YW Li, J Jiang, HF Yang, D Prabhakaran, ZK Liu, LX Yang, YL Chen

Disentangling orbital and spin exchange interactions for Co2+ on a rocksalt lattice

PHYSICAL REVIEW B 98 (2018) ARTN 024415

PM Sarte, RA Cowley, EE Rodriguez, E Pachoud, D Le, V Garcia-Sakai, JW Taylor, CD Frost, D Prabhakaran, C MacEwen, A Kitada, AJ Browne, M Songvilay, Z Yamani, WJL Buyers, JP Attfield, C Stock

Inelastic neutron scattering investigations of an anisotropic hybridization gap in the kondo insulators: CeT<inf>2</inf>Al<inf>10</inf>(T=Fe, Ru and Os)

Solid State Phenomena 257 (2017) 11-25

DT Adroja, Y Muro, T Takabatake, MD Le, HC Walker, KA McEwen, AT Boothroyd

� 2017 Trans Tech Publications, Switzerland. The recent discovery of topological Kondo insulating behaviour in strongly correlated electron systems has generated considerable interest in Kondo insulators both experimentally and theoretically. The Kondo semiconductors CeT2Al10(T=Fe, Ru and Os) possessing a c-f hybridization gap have received considerable attention recently because of the unexpected high magnetic ordering temperature of CeRu2Al10(TN=27 K) and CeOs2Al10(TN=28.5 K) and the Kondo insulating behaviour observed in the valence fluctuating compound CeFe2Al10with a paramagnetic ground state down to 50 mK. We are investigating this family of compounds, both in polycrystalline and single crystal form, using inelastic neutron scattering to understand the role of anisotropic c-f hybridization on the spin gap formation as well as on their magnetic properties. We have observed a clear sign of a spin gap in all three compounds from our polycrystalline study as well as the existence of a spin gap above the magnetic ordering temperature in T=Ru and Os. Our inelastic neutron scattering studies on single crystals of CeRu2Al10and CeOs2Al10revealed dispersive gapped spin wave excitations below TN. Analysis of the spin wave spectrum reveals the presence of strong anisotropic exchange, along the c-axis (or z-axis) stronger than in the ab-plane. These anisotropic exchange interactions force the magnetic moment to align along the c-axis, competing with the single ion crystal field anisotropy, which prefers moments along the a-axis. In the paramagnetic state (below 50 K) of the Kondo insulator CeFe2Al10, we have also observed dispersive gapped magnetic excitations which transform into quasi-elastic scattering on heating to 100 K. We will discuss the origin of the anisotropic hybridization gap in CeFe2Al10based on theoretical models of heavy-fermion semiconductors.

Crystal growth of pyrochlore rare-earth stannates

JOURNAL OF CRYSTAL GROWTH 468 (2017) 335-339

D Prabhakaran, S Wang, AT Boothroyd

Topological triplon modes and bound states in a Shastry-Sutherland magnet

NATURE PHYSICS 13 (2017) 736-+

PA McClarty, F Krueger, T Guidi, SF Parker, K Refson, AW Parker, D Prabhakaran, R Coldea