45 results on '"Hatnean, Monica Ciomaga"'
Search Results
2. Impact of disorder in Nd-based pyrochlore magnets
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Léger, Mélanie, Vayer, Florianne, Hatnean, Monica Ciomaga, Damay, Françoise, Decorse, Claudia, Berardan, David, Fåk, Björn, Zanotti, Jean-Marc, Berrod, Quentin, Embs, Jacques Ollivier Jan P., Fennell, Tom, Sheptyakov, Denis, Petit, Sylvain, and Lhotel, Elsa
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
We study the stability of the antiferromagnetic all-in--all-out state observed in dipolar-octupolar pyrochlores that have neodymium as the magnetic species. Different types of disorder are considered, either affecting the immediate environment of the Nd$^{3+}$ ion, or substituting it with a non-magnetic ion. Starting from the well studied Nd$_2$Zr$_2$O$_7$ compound, Ti substitution on the Zr site and dilution on the Nd magnetic site with La substitution are investigated. The recently discovered entropy stabilized compound NdMox, which exhibits a high degree of disorder on the non magnetic site is also studied. Using a range of experimental techniques, especially very low-temperature magnetization and neutron scattering, we show that the all-in--all-out state is very robust and withstands substitutional disorder up to large rates. From these measurements, we estimate the Hamiltonian parameters and discuss their evolution in the framework of the phase diagram of dipolar-octupolar pyrochlore magnets., Comment: 19 pages, 20 figures (main text: 12 pages, 13 figures)
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- 2024
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3. Charge doping into spin minority states mediates doubling of $T_\mathrm{C}$ in ferromagnetic CrGeTe$_3$
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Trzaska, Liam, Qiao, Lei, Watson, Matthew D., Hatnean, Monica Ciomaga, Marković, Igor, Morales, Edgar Abarca, Antonelli, Tommaso, Cacho, Cephise, Balakrishnan, Geetha, Ren, Wei, Picozzi, Silvia, and King, Phil D. C.
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Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The recent discovery of the persistence of long-range magnetic order when van der Waals layered magnets are thinned towards the monolayer limit has provided a tunable platform for the engineering of novel magnetic structures and devices. Here, we study the evolution of the electronic structure of CrGeTe$_3$ as a function of electron doping in the surface layer. From angle-resolved photoemission spectroscopy, we observe spectroscopic fingerprints that this electron doping drives a marked increase in $T_\mathrm{C}$, reaching values more than double that of the undoped material, in agreement with recent studies using electrostatic gating. Together with density functional theory calculations and Monte Carlo simulations, we show that, surprisingly, the increased $T_\mathrm{C}$ is mediated by the population of spin-minority Cr $t_{2g}$ states, forming a half-metallic 2D electron gas at the surface. We show how this promotes a novel variant of double exchange, and unlocks a significant influence of the Ge -- which was previously thought to be electronically inert in this system -- in mediating Cr-Cr exchange., Comment: 10 pages including supplementary information
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- 2023
4. Covalency, correlations, and inter-layer interactions governing the magnetic and electronic structure of Mn$_3$Si$_2$Te$_6$
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Bigi, Chiara, Qiao, Lei, Liu, Chao, Barone, Paolo, Hatnean, Monica Ciomaga, Siemann, Gesa-R., Achinuq, Barat, Mayoh, Daniel Alexander, Vinai, Giovanni, Polewczyk, Vincent, Dagur, Deepak, Mazzola, Federico, Bencok, Peter, Hesjedal, Thorsten, van der Laan, Gerrit, Ren, Wei, Balakrishnan, Geetha, Picozzi, Silvia, and King, Phil D. C.
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Condensed Matter - Materials Science - Abstract
Mn$_3$Si$_2$Te$_6$ is a rare example of a layered ferrimagnet. It has recently been shown to host a colossal angular magnetoresistance as the spin orientation is rotated from the in- to out-of-plane direction, proposed to be underpinned by a topological nodal-line degeneracy in its electronic structure. Nonetheless, the origins of its ferrimagnetic structure remain controversial, while its experimental electronic structure, and the role of correlations in shaping this, are little explored to date. Here, we combine x-ray and photoemission-based spectroscopies with first-principles calculations, to probe the elemental-selective electronic structure and magnetic order in Mn$_3$Si$_2$Te$_6$. Through these, we identify a marked Mn-Te hybridisation, which weakens the electronic correlations and enhances the magnetic anisotropy. We demonstrate how this strengthens the magnetic frustration in Mn$_3$Si$_2$Te$_6$, which is key to stabilising its ferrimagnetic order, and find a crucial role of both exchange interactions extending beyond nearest-neighbours and anti-symmetric exchange in dictating its ordering temperature. Together, our results demonstrate a powerful methodology of using experimental electronic structure probes to constrain the parameter space for first-principles calculations of magnetic materials, and through this approach, reveal a pivotal role played by covalency in stabilising the ferrimagnetic order in Mn$_3$Si$_2$Te$_6$.
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- 2023
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5. Direct measurement of a remnant Fermi surface in SmB6
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Millichamp, Thomas E., Billington, David, Robarts, Hannah C., Laverock, Jude, ONeill, Daniel, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Duffy, Jonathan A., Taylor, Jonathan W., Giblin, Sean R., and Dugdale, Stephen B.
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Condensed Matter - Strongly Correlated Electrons - Abstract
The quest to understand the nature of the electronic state in SmB6 has been challenging, perplexing and surprising researchers for over half a century. In the theoretically predicted topological Kondo insulator SmB6, the nature of the bulk electronic structure is not characterised unambiguously by quantum oscillations due to contrary interpretations. One simple definition of an electrical insulator is a material that lacks a Fermi surface and here we report the results of our investigation into its existence in SmB6 by Compton scattering. Compton scattering measures occupied electron momentum states, is bulk sensitive due to the high energy of the incoming photons and is also an ultra-fast probe of the correlated many-body electron wavefunction. Remarkably, direct evidence for a three-dimensional remnant Fermi surface is observed. However, a further dichotomy is raised in that the full occupancy expected of a conventional metal is not reproduced. Our observation of a remnant Fermi surface using a momentum-resolved probe provides significant new evidence that the paradigm of a bulk insulator is not robust for SmB6., Comment: 14 pages, 10 figures (Supplementary information included)
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- 2021
6. Impedance Spectroscopy of SmB$_6$ single crystals
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Stankiewicz, Jolanta, Blasco, Javier, Schlottmann, Pedro, Hatnean, Monica Ciomaga, and Balakrishnan, Geetha
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Condensed Matter - Strongly Correlated Electrons - Abstract
We report results from an in--plane and out--of--plane impedance study on SmB$_6$ single crystals, performed at low temperatures and over a wide frequency range. A universal equivalent circuit describes the dielectric behavior of this system across the transition, from surface to bulk dominated electrical conduction between 2 and 10 K. We identify the resistive, capacitive, and inductive contributions to the impedance. The equivalent inductance, obtained from fits to experimental data, drops drastically as the bulk starts to control electrical conduction upon increasing temperature. SmB$_6$ single crystals also show current--controlled negative differential resistance at low temperatures, which is brought about by Joule heating. This feature, in addition to inductive and capacitive contributions to the impedance, can give rise to the self--sustained voltage oscillations observed below 5 K (Stern {\it et al.}, Phys. Rev. Lett. {\bf 116}, 166603 (2016))., Comment: 14 pages, 6 figures
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- 2021
7. Intrinsic one-dimensional conducting channels in the Kondo insulator SmB6
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Xu, Ke-Jun, Barber, Mark, Ma, Eric Yue, Xia, Jing, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Zaanen, Jan, and Shen, Zhi-Xun
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
Since its discovery as a Kondo insulator 50 years ago, SmB6 recently received a revival of interest due to detection of unexpected quantum oscillations in the insulating state, discovery of disorder-immune bulk transport, and proposals of correlation-driven topological physics. While recent transport results attribute the anomalous low temperature conduction to two-dimensional surface states, important alternatives, such as conduction channel residing in one-dimensional dislocation lines, have not been adequately explored. Here we study SmB6 with scanning microwave impedance microscopy and uncover evidence for conducting one-dimensional states terminating at surface step edges. These states remain conducting up to room temperature, indicating unusual robustness against scattering and an unconventional origin. Our results bring to light a heretofore undetected conduction route in SmB6 that contributes to the low temperature transport. The unique scenario of intrinsic one-dimensional conducting channels in a highly insulating correlated bulk offers a one-dimensional platform that may host exotic physics., Comment: Upon further follow-up studies, we discovered additional data in different parameter spaces that weakened our arguments. While this does not preclude the existence of 1-D conducting states, we feel that our previous supporting arguments are rendered ineffective, and we must suspend and withdraw our manuscript at this point
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- 2021
8. Bulk transport paths through defects in floating zone and Al flux grown SmB$_6$
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Eo, Yun Suk, Rakoski, Alexa, Sinha, Shriya, Mihaliov, Dmitri, Fuhrman, Wesley T., Saha, Shanta R., Rosa, Priscila F. S., Fisk, Zachary, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Chamorro, Juan R., Koohpayeh, Seyed M., McQueen, Tyrel M., Kang, Boyoun, Song, Myung-suk, Cho, Beongki, Fuhrer, Michael S., Paglione, Johnpierre, and Kurdak, Cagliyan
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Condensed Matter - Strongly Correlated Electrons - Abstract
We investigate the roles of disorder on low-temperature transport in SmB$_6$ crystals grown by both the Al flux and floating zone methods. We used the inverted resistance method with Corbino geometry to investigate whether low-temperature variations in the standard resistance plateau arises from a surface or a bulk channel in floating zone samples. The results show significant sample-dependent residual bulk conduction, in contrast to smaller amounts of residual bulk conduction previously observed in Al flux grown samples with Sm vacancies. We consider hopping in an activated impurity band as a possible source for the observed bulk conduction, but it is unlikely that the large residual bulk conduction seen in floating zone samples is solely due to Sm vacancies. We therefore propose that one-dimensional defects, or dislocations, contribute as well. Using chemical etching, we find evidence for dislocations in both flux and floating zone samples, with higher dislocation density in floating zone samples than in Al flux grown samples. In addition to the possibility of transport through one-dimensional dislocations, we also discuss our results in the context of recent theoretical models of SmB$_6$., Comment: 22 pages, 4 figures
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- 2020
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9. Characterizing oxygen atoms in perovskite and pyrochlore oxides using ADF-STEM at a resolution of a few tens of picometers
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Mostaed, Ali, Walkley, Brant, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Lees, Martin R., Beanland, Richard, Sinclair, Derek C., and Reaney, Ian M.
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Condensed Matter - Materials Science - Abstract
We present an aberration corrected scanning transmission electron microscopy (ac-STEM) analysis of the perovskite (LaFeO3) and pyrochlore (Yb2Ti2O7 and Pr2Zr2O7) oxides and demonstrate that both the shape and contrast of visible atomic columns in annular dark-field (ADF) images are sensitive to the presence of nearby atoms of low atomic number (e.g. oxygen). We show that point defects (e.g. oxygen vacancies), which are invisible - or difficult to observe due to limited sensitivity - in X-ray and neutron diffraction measurements, are the origin of the complex magnetic ground state of pyrochlore oxides. In addition, we present, for the first time, a method by which light atoms can be resolved in quantitative ADF-STEM images. Using this method, we resolved oxygen atoms in perovskite and pyrochlore oxides., Comment: 18 pages and 7 figures plus supplementary information
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- 2020
10. Optical floating zone crystal growth of rare-earth disilicates, $R\mathbf{_{2}}$Si$\mathbf{_{2}}$O$\mathbf{_{7}}$ ($R=$ Er, Ho, and Tm)
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Hatnean, Monica Ciomaga, Petrenko, Oleg A., Lees, Martin R., Orton, Tom E., and Balakrishnan, Geetha
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Condensed Matter - Materials Science ,Condensed Matter - Other Condensed Matter ,Condensed Matter - Strongly Correlated Electrons - Abstract
The wealth of structural phases seen in the rare-earth disilicate compounds promises an equally rich range of interesting magnetic properties. We report on the crystal growth by the optical floating zone method of members of the rare-earth disilicate family, $R_{2}$Si$_{2}$O$_{7}$ (with $R=$ Er, Ho, and Tm). Through a systematic study, we have optimised the growth conditions for Er$_{2}$Si$_{2}$O$_{7}$. We have grown, for the first time using the floating zone method, crystal boules of Ho$_{2}$Si$_{2}$O$_{7}$ and Tm$_{2}$Si$_{2}$O$_{7}$ compounds. We show that the difficulties encountered in the synthesis of polycrystalline and single crystal samples are due to the similar thermal stability ranges of different rare-earth silicate compounds in the temperature-composition phase diagrams of the $R$-Si-O systems. The addition of a small amount of SiO$_{2}$ excess allowed the amount of impurity phases present in the powder samples to be minimised. The phase composition analysis of the powder X-ray diffraction data collected on the as-grown boules revealed that they were of single phase, except in the case of thulium disilicate, which comprised of two phases. All growths resulted in multi-grain boules, from which sizable single crystals could be isolated. The optimum conditions used for the synthesis and crystal growth of polycrystalline and single crystal $R_{2}$Si$_{2}$O$_{7}$ materials are reported. Specific heat measurements of erbium and thulium disilicate compounds confirm an antiferromagnetic phase transition below $T_{\mathrm{N}}=$ 1.8 K for D-type Er$_{2}$Si$_{2}$O$_{7}$ and a Schottky anomaly centered around 3.5 K in C-type Tm$_{2}$Si$_{2}$O$_{7}$, suggesting the onset of short-range magnetic correlations. Magnetic susceptibility data of E-type Ho$_{2}$Si$_{2}$O$_{7}$ reveals an antiferromagnetic ordering of the Ho spins below $T_\mathrm{{N}}=$ 2.3 K., Comment: 35 pages, 13 figures, 4 tables
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- 2020
11. Intrinsic bulk quantum oscillations in a bulk unconventional insulator SmB$_6$
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Hartstein, Mate, Liu, Hsu, Hsu, Yu-Te, Tan, Beng S., Hatnean, Monica Ciomaga, Balakrishnan, Geetha, and Sebastian, Suchitra E.
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Condensed Matter - Strongly Correlated Electrons - Abstract
The finding of bulk quantum oscillations in the bulk Kondo insulator SmB$_6$, which has been proposed to be a correlated topological insulator, proved a considerable surprise. The subsequent measurement of bulk quantum oscillations in other correlated insulators including YbB$_{12}$ have lent support to our discovery of a class of unconventional insulators that are host to bulk quantum oscillations, of which SmB$_6$ was the first example. Here we perform a series of experiments to examine evidence for the intrinsic character of bulk quantum oscillations in floating zone-grown single crystals of SmB$_6$ that have been the subject of our quantum oscillation studies thus far. We present results of experiments including chemical composition analysis, magnetisation, thermal conductivity, electrical transport, and heat capacity on floating zone-grown single crystals of SmB$_6$, and a series of quantum oscillation experiments as a function of magnetic field, temperature, and magnetic field-orientation on single crystals of floating-zone grown SmB$_6$, LaB$_6$, and elemental Aluminium. Results of these experimental studies establish the intrinsic origin of quantum oscillations from the bulk of pristine floating zone-grown single crystals of SmB$_6$. The origin of the underlying bulk Fermi surface that bears close similarity with the unhybridised Fermi surface in metallic hexaborides despite the bulk insulating character of SmB$_6$ is thus at the heart of a theoretical mystery.
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- 2020
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12. Emergent magnetic behaviour in the frustrated Yb$_3$Ga$_5$O$_{12}$ garnet
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Sandberg, Lise Orduk, Edberg, Richard, Pedersen, Kasper S., Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Mangin-Thro, Lucile, Wildes, Andrew, Fak, B., Ehlers, Georg, Sala, Gabriele, Henelius, Patrik, Lefmann, Kim, and Deen, Pascale P.
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Disordered Systems and Neural Networks ,Condensed Matter - Materials Science ,Condensed Matter - Other Condensed Matter - Abstract
We report neutron scattering, magnetic susceptibility and Monte Carlo theoretical analysis to verify the short range nature of the magnetic structure and spin-spin correlations in a Yb$_3$Ga$_5$O$_{12}$ single crystal. The quantum spin state of Yb$^{3+}$ in Yb$_3$Ga$_5$O$_{12}$ is verified. The quantum spins organise into a short ranged emergent director state for T $<$ 0.4 K derived from anisotropy and near neighbour exchange. We derive the magnitude of the near neighbour exchange interactions $0.6\; {\rm K} < J_1 < 0.7\; {\rm K}, J_2 = 0.12$~K and the magnitude of the dipolar exchange interaction, $D$, in the range $0.18 < D < 0.21$ K. Certain aspects of the broad experimental dataset can be modelled using a $J_1D$ model with ferromagnetic near neighbour spin-spin correlations while other aspects of the data can be accurately reproduced using a $J_1J_2D$ model with antiferromagnetic near neighbour spin-spin correlation. As such, although we do not quantify all the relevant exchange interactions we nevertheless provide a strong basis for the understanding of the complex Hamiltonian required to fully describe the magnetic state of Yb$_3$Ga$_5$O$_{12}$., Comment: Main paper 10 pages, appendix 6 pages
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- 2020
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13. Direct observation of the energy gain underpinning ferromagnetic superexchange in the electronic structure of CrGeTe$_3$
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Watson, Matthew D., Marković, Igor, Mazzola, Federico, Rajan, Akhil, Morales, Edgar A., Burn, David M., Hesjedal, Thorsten, van der Laan, Gerrit, Mukherjee, Saumya, Kim, Timur K., Bigi, Chiara, Vobornik, Ivana, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, and King, Philip D. C.
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
We investigate the temperature-dependent electronic structure of the van der Waals ferromagnet, CrGeTe$_3$. Using angle-resolved photoemission spectroscopy, we identify atomic- and orbital-specific band shifts upon cooling through ${T_\mathrm{C}}$. From these, together with x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we identify the states created by a covalent bond between the Te ${5p}$ and the Cr ${e_g}$ orbitals as the primary driver of the ferromagnetic ordering in this system, while it is the Cr ${t_{2g}}$ states that carry the majority of the spin moment. The ${t_{2g}}$ states furthermore exhibit a marked bandwidth increase and a remarkable lifetime enhancement upon entering the ordered phase, pointing to a delicate interplay between localized and itinerant states in this family of layered ferromagnets.
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- 2019
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14. Definitive Surface Magnetotransport Study of SmB$_{6}$
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Eo, Yun Suk, Wolgast, Steven, Rakoski, Alexa, Mihaliov, Dmitri, Kang, Boyoun, Song, Myung-suk, Cho, Beongki, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Fisk, Zachary, Saha, Shanta, Wang, Xiangfeng, Paglione, Johnpierre, and Kurdak, Cagliyan
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
After the theoretical prediction that SmB$_6$ is a topological Kondo insulator, there has been an explosion of studies on the SmB$_6$ surface. However, there is not yet an agreement on even the most basic quantities such as the surface carrier density and mobility. In this paper, we carefully revisit Corbino disk magnetotransport studies to find those surface transport parameters. We first show that subsurface cracks exist in the SmB$_6$ crystals, arising both from surface preparation and during the crystal growth. We provide evidence that these hidden subsurface cracks are additional conduction channels, and the large disagreement between earlier surface SmB$_6$ studies may originate from previous interpretations not taking this extra conduction path into account. We provide an update of a more reliable magnetotransport data than the previous one (Phys. Rev. B 92, 115110) and find that the orders-of-magnitude large disagreements in carrier density and mobility come from the surface preparation and the transport geometry rather than the intrinsic sample quality. From this magnetotransport study, we find an updated estimate of the carrier density and mobility of 2.71$\times$10$^{13}$ (1/cm$^2$) and 104.5 (cm$^{2}$/V$\cdot$sec), respectively. We compare our results with other studies of the SmB$_6$ surface. By this comparison, we provide insight into the disagreements and agreements of the previously reported angle-resolved photoemission spectroscopy, scanning tunneling microscopy, and magnetotorque quantum oscillations measurements.
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- 2019
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15. Neutron scattering signatures of a quantum spin ice
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Sibille, Romain, Gauthier, Nicolas, Yan, Han, Hatnean, Monica Ciomaga, Ollivier, Jacques, Winn, Barry, Filges, Uwe, Balakrishnan, Geetha, Kenzelmann, Michel, Shannon, Nic, and Fennell, Tom
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Condensed Matter - Strongly Correlated Electrons - Abstract
Quantum spin ice is an appealing proposal of a quantum spin liquid - systems where the magnetic moments of the constituent electron spins evade classical long-range order to form an exotic state that is quantum entangled and coherent over macroscopic length scales. Such phases are at the edge of our current knowledge in condensed matter as they go beyond the established paradigm of symmetry-breaking order and associated excitations. Neutron scattering experiments on the pyrochlore material Pr$_2$Hf$_2$O$_7$ reveal signatures of a quantum spin ice state that were predicted by theory., Comment: Article in Swiss Neutron News, after R. Sibille et al. Nature Physics 14, 711- 715 (2018). https://sgn.web.psi.ch/sgn/snn.html
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- 2019
16. Lattice dynamics and Raman spectrum of BaZrO3 single crystals
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Toulouse, Constance, Amoroso, Danila, Xin, Cong, Veber, Philippe, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Maglione, Mario, Ghosez, Philippe, Kreisel, Jens, and Guennou, Mael
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Condensed Matter - Materials Science - Abstract
BaZrO3 is a perovskite that remains in the simple cubic phase at all temperatures, hence with no first-order Raman-active phonon mode allowed by symmetry. Yet, it exhibits an intense Raman spectrum with sharp and well-defined features. Here, we report the evolution of the Raman spectrum of BaZrO3 single crystals in a broad temperature range (4--1200~K) and discuss its origin with the support of detailed first-principle calculations of the lattice dynamics. Phonon calculations are performed not only for the cubic phase of BaZrO3, but also for the low-symmetry phases with octahedra tilts that have been suspected to exist at the nanoscale. We show that the Raman spectrum shows no direct evidence for these nanodomains, but can instead be explained by classical second-order Raman scattering. We provide an assignment of the dominant features to phonon modes combinations. In particular, we show that the high frequency range of the spectrum is dominated by overtones and shows an image of the phonon density of states corresponding to the stretching modes of the oxygen octahedra.
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- 2019
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17. Dielectric and transient electrical response of SmB6 single crystals
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Stankiewicz, Jolanta, Schlottmann, Pedro, Blasco, Javier, Hatnean, Monica Ciomaga, and Balakrishnan, Geetha
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- 2023
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18. Impact of disorder in Nd-based pyrochlore magnets
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Léger, Mélanie, primary, Vayer, Florianne, additional, Hatnean, Monica Ciomaga, additional, Damay, Françoise, additional, Decorse, Claudia, additional, Berardan, David, additional, Fåk, Björn, additional, Zanotti, Jean-Marc, additional, Berrod, Quentin, additional, Ollivier, Jacques, additional, Embs, Jan P., additional, Fennell, Tom, additional, Sheptyakov, Denis, additional, Petit, Sylvain, additional, and Lhotel, Elsa, additional
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- 2024
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19. Investigating the magnetic ground state of the skyrmion host material Cu$_{2}$OSeO$_{3}$ using long-wavelength neutron diffraction
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Franke, Kévin J. A., Dean, Philip R., Hatnean, Monica Ciomaga, Birch, Max T., Khalyavin, Dmitry, Manuel, Pascal, Lancaster, Tom, Balakrishnan, Geetha, and Hatton, Peter D.
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Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
We present long-wavelength neutron diffraction data measured on both single crystal and polycrystalline samples of the skyrmion host material Cu$_{2}$OSeO$_{3}$. We observe magnetic satellites around the $(0\bar{1}1)$ diffraction peak not accessible to other techniques, and distinguish helical from conical spin textures in reciprocal space. We confirm successive transitions from helical to conical to field polarised ordered spin textures as the external magnetic field is increased. The formation of a skyrmion lattice with propagation vectors perpendicular to the field direction is observed in a region of the field-temperature phase diagram that is consistent with previous reports. Our measurements show that not only the field-polarised phase but also the helical ground state are made up of ferrimagnetic clusters instead of individual spins. These clusters are distorted Cu tetrahedra, where the spin on one Cu ion is anti-aligned with the spin on the three other Cu ions.
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- 2018
20. Magnetic phases of skyrmion-hosting GaV$_4$S$_{8-y}$Se$_{y}$ ($y = 0, 2, 4, 8$) probed with muon spectroscopy
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Franke, Kévin J. A., Huddart, Benjamin M., Hicken, Thomas J., Xiao, Fan, Blundell, Stephen J., Pratt, Francis L., Crisanti, Marta, Barker, Joel, Clark, Stewart J., Štefančič, Aleš, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, and Lancaster, Tom
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Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
We present the results of a muon-spin spectroscopy investigation of GaV$_4$S$_{8-y}$Se$_{y}$ with $y=0, 2, 4$ and 8. Zero-field measurements suggest that GaV$_{4}$Se$_{8}$ and GaV$_{4}$S$_{8}$ have distinct magnetic ground states, with the latter material showing an anomalous temperature-dependence of the local magnetic field. It is not possible to evolve the magnetic state continuously between these two systems, with the intermediate $y=2$ and $4$ materials showing glassy magnetic behaviour at low temperature. The skyrmion lattice (SkL) phase is evident in the $y=0$ and 8 materials through an enhanced response of the muon-spin relaxation to the emergent dynamics that accompany the SkL. For our polycrystalline samples of GaV$_4$Se$_{8}$, this enhanced dynamic response is confined to a smaller region of the magnetic field-temperature phase diagram than the previous reports of the SkL in single crystals.
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- 2018
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21. Fermi surfaces in Kondo insulators
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Liu, Hsu, Hartstein, Mate, Wallace, Gregory J., Davies, Alexander J., Hatnean, Monica Ciomaga, Johannes, Michelle D., Shitsevalova, Natalya, Balakrishnan, Geetha, and Sebastian, Suchitra E.
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Condensed Matter - Strongly Correlated Electrons - Abstract
We report magnetic quantum oscillations measured using torque magnetisation in the Kondo insulator YbB$_{12}$ and discuss the potential origin of the underlying Fermi surface. Observed quantum oscillations as well as complementary quantities such as a finite linear specific heat capacity in YbB$_{12}$ exhibit similarities with the Kondo insulator SmB$_6$, yet also crucial differences. Small heavy Fermi sections are observed in YbB$_{12}$ with similarities to the neighbouring heavy fermion semimetallic Fermi surface, in contrast to large light Fermi surface sections in SmB$_6$ which are more similar to the conduction electron Fermi surface. A rich spectrum of theoretical models is suggested to explain the origin across different Kondo insulating families of a bulk Fermi surface potentially from novel itinerant quasiparticles that couple to magnetic fields, yet do not couple to weak DC electric fields., Comment: Journal of Physics: Condensed Matter (2018)
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- 2018
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22. Experimental signatures of emergent quantum electrodynamics in Pr$_2$Hf$_2$O$_7$
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Sibille, Romain, Gauthier, Nicolas, Yan, Han, Hatnean, Monica Ciomaga, Ollivier, Jacques, Winn, Barry, Filges, Uwe, Balakrishnan, Geetha, Kenzelmann, Michel, Shannon, Nic, and Fennell, Tom
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science - Abstract
In a quantum spin liquid, the magnetic moments of the constituent electron spins evade classical long-range order to form an exotic state that is quantum entangled and coherent over macroscopic length scales [1-2]. Such phases offer promising perspectives for device applications in quantum information technologies, and their study can reveal fundamentally novel physics in quantum matter. Quantum spin ice is an appealing proposal of one such state, in which the fundamental ground state properties and excitations are described by an emergent U(1) lattice gauge theory [3-7]. This quantum-coherent regime has quasiparticles that are predicted to behave like magnetic and electric monopoles, along with a gauge boson playing the role of an artificial photon. However, this emergent lattice quantum electrodynamics has proved elusive in experiments. Here we report neutron scattering measurements of the rare-earth pyrochlore magnet Pr$_2$Hf$_2$O$_7$ that provide evidence for a quantum spin ice ground state. We find a quasi-elastic structure factor with pinch points - a signature of a classical spin ice - that are partially suppressed, as expected in the quantum-coherent regime of the lattice field theory at finite temperature. Our result allows an estimate for the speed of light associated with magnetic photon excitations. We also reveal a continuum of inelastic spin excitations, which resemble predictions for the fractionalized, topological excitations of a quantum spin ice. Taken together, these two signatures suggest that the low-energy physics of Pr$_2$Hf$_2$O$_7$ can be described by emergent quantum electrodynamics. If confirmed, the observation of a quantum spin ice ground state would constitute a concrete example of a three-dimensional quantum spin liquid - a topical state of matter which has so far mostly been explored in lower dimensionalities., Comment: 15 pages, 3 figures
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- 2017
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23. Single crystal growth, structure and magnetic properties of Pr2Hf2O7 pyrochlore
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Hatnean, Monica Ciomaga, Sibille, Romain, Lees, Martin R., Kenzelmann, Michel, Ban, Voraksmy, Pomjakushin, Vladimir, and Balakrishnan, Geetha
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Condensed Matter - Materials Science - Abstract
Large single crystals of the pyrochlore Pr2Hf2O7 have been successfully grown by the floating zone technique using an optical furnace equipped with high power Xenon arc lamps. Structural investigations have been carried out by both synchrotron X-ray and neutron powder diffraction to establish the crystallographic structure of the materials produced. The magnetic properties of the single crystals have been determined for magnetic fields applied along different crystallographic axes. The results reveal that Pr2Hf2O7 is an interesting material for further investigations as a frustrated magnet. The high quality of the crystals produced make them ideal for detailed investigations, especially those using neutron scattering techniques., Comment: Accepted for publication in J. Phys.: Condens. Matter
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- 2016
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24. Coulomb spin liquid in anion-disordered pyrochlore Tb$_2$Hf$_2$O$_7$
- Author
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Sibille, Romain, Lhotel, Elsa, Hatnean, Monica Ciomaga, Nilsen, Gøran, Ehlers, Georg, Cervellino, Antonio, Ressouche, Eric, Frontzek, Matthias, Zaharko, Oksana, Pomjakushin, Vladimir, Stuhr, Uwe, Walker, Helen C., Adroja, Devashibhai, Luetkens, Hubertus, Baines, Chris, Amato, Alex, Balakrishnan, Geetha, Fennell, Tom, and Kenzelmann, Michel
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
The charge ordered structure of ions and vacancies characterizing rare-earth pyrochlore oxides serves as a model for the study of geometrically frustrated magnetism. The organization of magnetic ions into networks of corner-sharing tetrahedra gives rise to highly correlated magnetic phases with strong fluctuations, including spin liquids and spin ices. It is an open question how these ground states governed by local rules are affected by disorder. In the pyrochlore Tb$_2$Hf$_2$O$_7$, we demonstrate that the vicinity of the disordering transition towards a defective fluorite structure translates into a tunable density of anion Frenkel disorder while cations remain ordered. Quenched random crystal fields and disordered exchange interactions can therefore be introduced into otherwise perfect pyrochlore lattices of magnetic ions. We show that disorder can play a crucial role in preventing long-range magnetic order at low temperatures, and instead induces a strongly-fluctuating Coulomb spin liquid with defect-induced frozen magnetic degrees of freedom., Comment: 18 pages, 4 figures, + Supplementary Information (4 figures)
- Published
- 2016
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25. Candidate quantum spin ice in the pyrochlore Pr$_2$Hf$_2$O$_7$
- Author
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Sibille, Romain, Lhotel, Elsa, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Fåk, Björn, Gauthier, Nicolas, Fennell, Tom, and Kenzelmann, Michel
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
We report the low temperature magnetic properties of the pyrochlore Pr$_2$Hf$_2$O$_7$. Polycrystalline and single-crystal samples are investigated using time-of-flight neutron spectroscopy and macroscopic measurements, respectively. The crystal-field splitting produces a non-Kramers doublet ground state for Pr$^{3+}$, with Ising-like anisotropy. Below 0.5 K ferromagnetic correlations develop, which suggests that the system enters a spin ice-like state associated with the metamagnetic behavior observed at $\mu_0H_c\sim2.4$~T. In this regime, the development of a discrete inelastic excitation in the neutron spectra indicates the appearance of spin dynamics which are likely related to cooperative quantum fluctuations., Comment: 7 pages, 5 figures, 1 table
- Published
- 2016
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26. Characterizing oxygen atoms in perovskite and pyrochlore oxides using ADF-STEM at a resolution of a few tens of picometers
- Author
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Mostaed, Ali, Walkley, Brant, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Lees, Martin R., Beanland, Richard, Sinclair, Derek C., and Reaney, Ian M.
- Published
- 2021
- Full Text
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27. Covalency, correlations, and interlayer interactions governing the magnetic and electronic structure of Mn3Si2Te6
- Author
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Bigi, Chiara, primary, Qiao, Lei, additional, Liu, Chao, additional, Barone, Paolo, additional, Hatnean, Monica Ciomaga, additional, Siemann, Gesa-R., additional, Achinuq, Barat, additional, Mayoh, Daniel Alexander, additional, Vinai, Giovanni, additional, Polewczyk, Vincent, additional, Dagur, Deepak, additional, Mazzola, Federico, additional, Bencok, Peter, additional, Hesjedal, Thorsten, additional, van der Laan, Gerrit, additional, Ren, Wei, additional, Balakrishnan, Geetha, additional, Picozzi, Silvia, additional, and King, Phil D. C., additional
- Published
- 2023
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28. Magnetic structures of geometrically frustrated SrGd$_2$O$_4$ derived from powder and single-crystal neutron diffraction
- Author
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Qureshi, N., Malkin, B. Z., Riberolles, S. X. M., Ritter, C., Ouladdiaf, B., Balakrishnan, Geetha, Hatnean, Monica Ciomaga, and Petrenko, Oleg
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences ,QD ,QC - Abstract
We present the low-temperature magnetic structures of SrGd$_2$O$_4$ combining neutron diffraction methods on polycrystalline and single-crystal samples containing the $^{160}$Gd isotope. In contrast to other members of the Sr$Ln_2$O$_4$ family ($Ln$ = lanthanide) this system reveals two long-range ordered magnetic phases, which our diffraction data unambiguously identify. Below $T_{\rm N1}$ = 2.73~K, a $\mathbf{q}_1$ = (0 0 0) magnetic structure is stabilized where ferromagnetic chains along the $c$~axis (space group $Pnam$) are coupled antiferromagnetically with neighboring chains. On cooling below $T_{\rm N2}$ = 0.48~K, an additional incommensurate component modulated by $\mathbf{q}_2$ = (0~0~0.42) evolves and aligned along either of the perpendicular axes for the two different Gd sites, resulting in a fan-like magnetic structure. The identification of the particular Gd sites with the magnetic order observed with neutron diffraction is facilitated by a detailed analysis of the crystal fields acting on the sites. The observed ordering phenomena underline the complex multiaxial anisotropy in this system.
- Published
- 2022
29. Dielectric and Transient Electrical Response of Smb6 Single Crystals
- Author
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Stankiewicz, Jolanta, primary, Schlottmann, Pedro, additional, Blasco, Javier, additional, Hatnean, Monica Ciomaga, additional, and Balakrishnan, Geetha, additional
- Published
- 2022
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30. Fragile ground state and rigid field-induced structures in the zigzag ladder compound BaDy2O4
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Khalyavin, D. D., Manuel, P., Hatnean, Monica Ciomaga, and Petrenko, Oleg
- Subjects
QC - Abstract
We report on a sequence of field-induced transitions in the zigzag ladder compound BaDy2O4 studied with powder neutron diffraction and magnetization measurements. In agreement with the previously published results, the low-temperature zero-field structure is characterized by two half-integer propagation vectors k1=[1/2 0 1/2] and k2=[1/2 1/2 1/2]. However, on application of an external magnetic field, the Bragg peaks corresponding to the zero-field structure lose their intensity rather rapidly and disappear completely in a field of 2.5 kOe. In the intermediate fields, 2.5 to 22.5 kOe, new peaks are observed characterized by the propagation vector k′=[0 0 1/3] corresponding to an up-up-down (uud) structure as well as the k= 0 ferromagnetic peaks. This regime of fields corresponds to a pronounced plateau in the magnetization curve. Remarkably, the uud structure survives heating to at least 1.4 K, three times higher temperature than the TN of 0.48 K for the zero-field structure. Above 22.5 kOe, the k' peaks disappear while the k=0 peaks gain significant intensity indicating an increase in the polarization of the system. The analysis of the intensities of the field-induced reflections allows for a clear identification of the magnetic structures in both the intermediate- and high-field regimes.
- Published
- 2021
31. Emergent magnetic behavior in the frustrated Yb3Ga5O12 garnet
- Author
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Sandberg, Lise Ørduk, primary, Edberg, Richard, additional, Bakke, Ingrid-Marie Berg, additional, Pedersen, Kasper S., additional, Hatnean, Monica Ciomaga, additional, Balakrishnan, Geetha, additional, Mangin-Thro, Lucile, additional, Wildes, Andrew, additional, Fåk, B., additional, Ehlers, Georg, additional, Sala, Gabriele, additional, Henelius, Patrik, additional, Lefmann, Kim, additional, and Deen, Pascale P., additional
- Published
- 2021
- Full Text
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32. Bulk transport paths through defects in floating zone and Al flux grown SmB6
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Eo, Yun Suk, primary, Rakoski, Alexa, additional, Sinha, Shriya, additional, Mihaliov, Dmitri, additional, Fuhrman, Wesley T., additional, Saha, Shanta R., additional, Rosa, Priscila F. S., additional, Fisk, Zachary, additional, Hatnean, Monica Ciomaga, additional, Balakrishnan, Geetha, additional, Chamorro, Juan R., additional, Phelan, W. Adam, additional, Koohpayeh, Seyed M., additional, McQueen, Tyrel M., additional, Kang, Boyoun, additional, Song, Myung-suk, additional, Cho, Beongki, additional, Fuhrer, Michael S., additional, Paglione, Johnpierre, additional, and Kurdak, Çağlıyan, additional
- Published
- 2021
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- View/download PDF
33. Lattice dynamics and Raman spectrum of BaZrO3 single crystals
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Toulouse, Constance, primary, Amoroso, Danila, additional, Xin, Cong, additional, Veber, Philippe, additional, Hatnean, Monica Ciomaga, additional, Balakrishnan, Geetha, additional, Maglione, Mario, additional, Ghosez, Philippe, additional, Kreisel, Jens, additional, and Guennou, Mael, additional
- Published
- 2019
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34. Magnetic phases of skyrmion-hosting GaV4S8-ySey (y=0, 2, 4, 8) probed with muon spectroscopy
- Author
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Franke, Kévin J. A., Huddart, Benjamin M., Hicken, Thomas J., Xiao, Fan, Blundell, Stephen J., Pratt, Francis L., Crisanti, Marta, Barker, Joel A. T., Clark, Stewart J., Štefančič, Aleš, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, and Lancaster, Tom
- Subjects
QC - Abstract
We present the results of a muon-spin spectroscopy investigation of GaV4S8−ySey with y = 0, 2, 4, and 8. Zero-field measurements suggest that GaV4Se8 and GaV4S8 have distinct magnetic ground states, with the latter material showing an anomalous temperature dependence of the local magnetic field. It is not possible to evolve the magnetic state continuously between these two systems, with the intermediate y = 2 and 4 materials showing glassy magnetic behavior at low temperature. The skyrmion lattice (SkL) phase is evident in the y = 0 and 8 materials through an enhanced response of the muon-spin relaxation to the emergent dynamics that accompany the SkL. For our polycrystalline samples of GaV4Se8, this enhanced dynamic response is confined to a smaller region of the magnetic field-temperature phase diagram than the previous reports of the SkL in single crystals.
- Published
- 2018
35. Investigating the magnetic ground state of the skyrmion host material Cu$_{2}$OSeO$_{3}$ using long-wavelength neutron diffraction
- Author
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Franke, K��vin J. A., Dean, Philip R., Hatnean, Monica Ciomaga, Birch, Max T., Khalyavin, Dmitry, Manuel, Pascal, Lancaster, Tom, Balakrishnan, Geetha, and Hatton, Peter D.
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons ,Strongly Correlated Electrons (cond-mat.str-el) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences - Abstract
We present long-wavelength neutron diffraction data measured on both single crystal and polycrystalline samples of the skyrmion host material Cu$_{2}$OSeO$_{3}$. We observe magnetic satellites around the $(0\bar{1}1)$ diffraction peak not accessible to other techniques, and distinguish helical from conical spin textures in reciprocal space. We confirm successive transitions from helical to conical to field polarised ordered spin textures as the external magnetic field is increased. The formation of a skyrmion lattice with propagation vectors perpendicular to the field direction is observed in a region of the field-temperature phase diagram that is consistent with previous reports. Our measurements show that not only the field-polarised phase but also the helical ground state are made up of ferrimagnetic clusters instead of individual spins. These clusters are distorted Cu tetrahedra, where the spin on one Cu ion is anti-aligned with the spin on the three other Cu ions.
- Published
- 2018
36. Magnetic phases of skyrmion-hostingGaV4S8−ySey(y=0,2,4,8)probed with muon spectroscopy
- Author
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Franke, Kévin J. A., primary, Huddart, Benjamin M., additional, Hicken, Thomas J., additional, Xiao, Fan, additional, Blundell, Stephen J., additional, Pratt, Francis L., additional, Crisanti, Marta, additional, Barker, Joel A. T., additional, Clark, Stewart J., additional, Štefančič, Aleš, additional, Hatnean, Monica Ciomaga, additional, Balakrishnan, Geetha, additional, and Lancaster, Tom, additional
- Published
- 2018
- Full Text
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37. Fermi surfaces in Kondo insulators
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Liu, Hsu, primary, Hartstein, Máté, additional, Wallace, Gregory J, additional, Davies, Alexander J, additional, Hatnean, Monica Ciomaga, additional, Johannes, Michelle D, additional, Shitsevalova, Natalya, additional, Balakrishnan, Geetha, additional, and Sebastian, Suchitra E, additional
- Published
- 2018
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38. Structural and magnetic investigations of new skyrmion phases
- Author
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Balakrishnan, Geetha, primary, Hatnean, Monica Ciomaga, additional, Stefancic, Ales, additional, and Lees, Martin R., additional
- Published
- 2017
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39. Single crystal growth, structure and magnetic properties of Pr2Hf2O7pyrochlore
- Author
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Hatnean, Monica Ciomaga, primary, Sibille, Romain, additional, Lees, Martin R, additional, Kenzelmann, Michel, additional, Ban, Voraksmy, additional, Pomjakushin, Vladimir, additional, and Balakrishnan, Geetha, additional
- Published
- 2016
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- View/download PDF
40. Structural disorder in a magnetic pyrochlore oxide
- Author
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Sibille, Romain, primary, Fennell, Tom, additional, Hatnean, Monica Ciomaga, additional, Lhotel, Elsa, additional, Keen, David, additional, Balakrishnan, Geetha, additional, and Kenzelmann, Michel, additional
- Published
- 2016
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41. Candidate quantum spin ice in the pyrochlorePr2Hf2O7
- Author
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Sibille, Romain, primary, Lhotel, Elsa, additional, Hatnean, Monica Ciomaga, additional, Balakrishnan, Geetha, additional, Fåk, Björn, additional, Gauthier, Nicolas, additional, Fennell, Tom, additional, and Kenzelmann, Michel, additional
- Published
- 2016
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42. C1. Tuning the properties of materials through crystal growth.
- Author
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Ciomaga Hatnean, Vasile Cristian, Simonov, Arkadiy, Hatnean, Monica Ciomaga, and Pui, Aurel
- Subjects
CRYSTAL growth ,SINGLE crystals ,INTERATOMIC distances ,THERMAL expansion ,RARE earth metals - Abstract
An important part of the materials used in the everyday life are in polycrystalline form and most of them have been extracted from the earth’s crust or synthesized using different synthesis methods. Using the approach of a chemist, we are looking into how to enhance some of the properties (electric, magnetic, and structural) of the materials found in everyday life devices. To this extent, our work focuses on understanding if the properties of interest have their origin in the crystallographic structure of the solid and/or how much they are influenced by microstructural parameters. It is well known, for some time, that nano-particles, the bi-dimensional materials or even thin layers have different properties than the bulk material due to new interesting phenomena originating in their 1D, 2D nano-scale size or resulting from the interaction with the substrate. It is thus crucial to achieve a better understanding of the source of the properties of a “perfect” material, i.e. the single crystal. The availability of a material in the form of a single crystal will give us access to the intrinsic properties of the compound, un-altered by the interaction with the substrate, grain boundaries, etc. Once the origin of the properties of a material has been elucidated, a chemist could envisage applying chemical pressure through doping with a similar sized ion as a mean to change inter-atomic distances and tune the desired property. The present study involves the synthesis, characterization and improvement of a series of compounds that are potential candidates for environmental barriers. Most of the environmental barriers used in different application are polycrystalline samples that are very well compacted. A high number of crystalline materials have anisotropic properties, originating in their crystallographic structure, thus it is important to study the properties of the single crystal form of these materials [1]. This will allow the enhancement of the properties that are significant in environmental barrier applications: thermal insulation, chemical resistance, as well as hardness and the compactness through the thermal expansion coefficient. It is well known that the rare earth silicates are a good candidate for such applications that require high temperature, however through studies of their single crystals we can improve the properties and extend their applicability [2]. [ABSTRACT FROM AUTHOR]
- Published
- 2023
43. Zirconate Pyrochlore Frustrated Magnets: Crystal Growth by the Floating Zone Technique.
- Author
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Hatnean, Monica Ciomaga, Decorse, Claudia, Lees, Martin R., Petrenko, Oleg A., and Balakrishnan, Geetha
- Subjects
RARE earth metals ,PYROCHLORE ,CRYSTALLOGRAPHY - Abstract
This article reviews recent achievements on the crystal growth of a new series of pyrochlore oxides-lanthanide zirconates, which are frustrated magnets with exotic magnetic properties. Oxides of the type A
2 B2 O7 (where A = Rare Earth, B = Ti, Mo) have been successfully synthesised in single crystal form using the floating zone method. The main difficulty of employing this technique for the growth of rare earth zirconium oxides A2 Zr2 O7 arises from the high melting point of these materials. This drawback has been recently overcome by the use of a high power Xenon arc lamp furnace for the growth of single crystals of Pr2 Zr2 O7 . Subsequently, large, high quality single crystals of several members of the zirconate family of pyrochlore oxides A2 Zr2 O7 (with A = La→Gd) have been grown by the floating zone technique. In this work, the authors give an overview of the crystal growth of lanthanide zirconates. The optimum conditions used for the floating zone growth of A2 Zr2 O7 crystals are reported. The characterisation of the crystal boules and their crystal quality is also presented. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
44. Candidate quantum spin ice in the pyrochlore Pr2Hf2O7.
- Author
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Sibille, Romain, Lhotel, Elsa, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, Fåk, Björn, Gauthier, Nicolas, Fennell, Tom, and Kenzelmann, Michel
- Subjects
- *
PYROCHLORE , *PRASEODYMIUM , *QUANTUM spin models - Abstract
We report the low temperature magnetic properties of the pyrochlore Pr2Hf2O7. Polycrystalline and single-crystal samples are investigated using time-of-flight neutron spectroscopy and macroscopic measurements, respectively. The crystal-field splitting produces a non-Kramers doublet ground state for Pr3+, with Ising-like anisotropy. Below 0.5 K ferromagnetic correlations develop, which suggests that the system enters a spin-ice-like state associated with the metamagnetic behavior observed at μ0Hc∼2.4 T. In this regime, the development of a discrete inelastic excitation in the neutron spectra indicates the appearance of spin dynamics that are likely related to cooperative quantum fluctuations. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
45. Single crystal growth, structure and magnetic properties of Pr 2 Hf 2 O 7 pyrochlore.
- Author
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Hatnean MC, Sibille R, Lees MR, Kenzelmann M, Ban V, Pomjakushin V, and Balakrishnan G
- Abstract
Large single crystals of pyrochlore [Formula: see text] were successfully grown by the floating zone technique using an optical furnace equipped with high power xenon arc lamps. Structural investigations were carried out via powder synchrotron x-ray and neutron diffraction to establish the crystallographic structure of the materials produced. The magnetic properties of the single crystals were determined for magnetic fields applied along different crystallographic axes. The results revealed that [Formula: see text] is an interesting material for further investigation as a frustrated magnet. The high quality of the crystals produced makes them ideal for detailed investigation, especially using neutron scattering techniques.
- Published
- 2017
- Full Text
- View/download PDF
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