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Bordács S, Butykai A, Szigeti BG, White JS, Cubitt R, Leonov AO, Widmann S, Ehlers D, von Nidda HAK, Tsurkan V, Loidl A, Kézsmárki I. Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet. Sci Rep 2017; 7:7584. [PMID: 28790441 PMCID: PMC5548730 DOI: 10.1038/s41598-017-07996-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 07/04/2017] [Indexed: 11/09/2022] Open
Abstract
The skyrmion lattice state (SkL), a crystal built of mesoscopic spin vortices, gains its stability via thermal fluctuations in all bulk skyrmion host materials known to date. Therefore, its existence is limited to a narrow temperature region below the paramagnetic state. This stability range can drastically increase in systems with restricted geometries, such as thin films, interfaces and nanowires. Thermal quenching can also promote the SkL as a metastable state over extended temperature ranges. Here, we demonstrate more generally that a proper choice of material parameters alone guarantees the thermodynamic stability of the SkL over the full temperature range below the paramagnetic state down to zero kelvin. We found that GaV4Se8, a polar magnet with easy-plane anisotropy, hosts a robust Néel-type SkL even in its ground state. Our supporting theory confirms that polar magnets with weak uniaxial anisotropy are ideal candidates to realize SkLs with wide stability ranges.
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Affiliation(s)
- S Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - A Butykai
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - B G Szigeti
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - J S White
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232, Villigen, Switzerland
| | - R Cubitt
- Institut Laue-Langevin, 6 rue Jules Horowitz, 38042, Grenoble, France
| | - A O Leonov
- Center for Chiral Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.,Department of Chemistry, Faculty of Science, Hiroshima University Kagamiyama, Higashi Hiroshima, Hiroshima, 739-8526, Japan
| | - S Widmann
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - D Ehlers
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - H-A Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany.,Institute of Applied Physics, Academy of Sciences of Moldova, MD, 2028, Chisinau, Republic of Moldova
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - I Kézsmárki
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary. .,Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany.
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2
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Mack T, Ruff A, Krug von Nidda HA, Loidl A, Krohns S. Dielectric properties of complex magnetic field induced states in PbCuSO 4(OH) 2. Sci Rep 2017; 7:4460. [PMID: 28667324 PMCID: PMC5493698 DOI: 10.1038/s41598-017-04752-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 05/22/2017] [Indexed: 11/19/2022] Open
Abstract
Spin spirals, which coexist with collinear spin order in linarite PbCuSO4(OH)2, indicate electrical polarisation textures of spin-multipolar phases. We derive experimental evidence by a detailed investigation of the magnetic-field dependent dielectric and electric polarization properties at low temperatures. Linarite exhibits a quasi-one-dimensional frustrated S = ½ spin chain, which forms 3D spin-spiral order in zero magnetic field for T < 2.85 K. Recently, due to the monoclinic lattice of linarite with CuO2 ribbon chains, complex magnetic field induced states were found. These spin-multipolar phases, which compete with spin-density waves at low magnetic fields, exist in close vicinity to the transition from the spin spiral into field induced spin polarized state. Via antisymmetric Dzyaloshinskii-Moriya interaction spin-driven ferroelectricity develops in the spin-spirals state. Via electric polarization measurements this allows to prove the transitions into complex magnetic field induced phases. Thorough analyses of the temperature and magnetic field dependent dielectric properties of a naturally grown single crystalline sample provide a detailed (T,H) phase diagrams for the three different crystallographic directions.
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Affiliation(s)
- T Mack
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - A Ruff
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - H-A Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - S Krohns
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany.
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Ehlers D, Stasinopoulos I, Kézsmárki I, Fehér T, Tsurkan V, von Nidda HAK, Grundler D, Loidl A. Exchange anisotropy in the skyrmion host GaV 4S 8. J Phys Condens Matter 2017; 29:065803. [PMID: 28002048 DOI: 10.1088/1361-648x/aa4e7e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Using ferromagnetic resonance spectroscopy at 34 GHz we explored the magnetic anisotropy of single-crystalline GaV4S8 in the field-polarized magnetic state. We describe the data in terms of an easy-axis type uniaxial anisotropy with an anisotropy constant [Formula: see text] erg cm-3 at 2 K, corresponding to a relative exchange anisotropy [Formula: see text]%, and about [Formula: see text]erg cm-3 near 11 K, i.e. at temperatures where the skyrmion-lattice phase was recently discovered. The relatively large value of K 1 explains the confinement of the skyrmion tubes to the [Formula: see text] easy axes. A distinct set of resonances in the spectra is attributed to the co-existence of different rhombohedral domains. Complementary broadband spectroscopy demonstrates that non-collinear spin states may sensitively be detected by electron spin resonance techniques.
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Affiliation(s)
- D Ehlers
- Experimentalphysik V, Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, 86135 Augsburg, Germany
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4
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Felea V, Yasin S, Günther A, Deisenhofer J, Krug von Nidda HA, Scheidt EW, Quach DV, Groza JR, Zherlitsyn S, Tsurkan V, Lemmens P, Wosnitza J, Loidl A. Ultrasound study of FeCr2S4 in high magnetic fields. J Phys Condens Matter 2014; 26:486001. [PMID: 25366066 DOI: 10.1088/0953-8984/26/48/486001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on ultrasound studies of FeCr2S4 in static and pulsed magnetic fields exhibiting an orbital-order transition at 9 K. A longitudinal acoustic mode exhibits distinct features in the phase space of temperature and magnetic field due to magnetic and structural transformations. Pulsed-field measurements show significant differences in the sound velocity below and above the orbital-ordering transition as well as the spin-reorientation transition at 60 K. Our results indicate a reduction of the magnetocrystalline anisotropy on entering the orbitally ordered phase.
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Affiliation(s)
- V Felea
- Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau MD-2028, Republic of Moldova
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5
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Riegg S, Widmann S, Günther A, Krug von Nidda HA, Reller A, Loidl A, Ebbinghaus SG. Suppression of Ru (S = 1) spin dimerization in La2RuO5 by Ti substitution. J Phys Condens Matter 2013; 25:126002. [PMID: 23449121 DOI: 10.1088/0953-8984/25/12/126002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
La2RuO5 shows a magneto-structural phase transition at 161 K with spin dimerization and concomitant formation of a non-magnetic singlet ground state. To gain a deeper insight into the origin of this transition systematic substitution of Ru by Ti has been carried out. Polycrystalline samples have been synthesized by thermal decomposition of citrate precursors leading to La2Ru(1-y)Ti(y)O5 (0 ≤ y ≤ 0.45). The crystal structure was investigated by x-ray powder diffraction at room temperature and at 100 K. The valences of Ti and Ru were obtained from x-ray absorption near edge structure spectroscopy at the Ti-K and the Ru-LIII absorption edges, respectively. The magnetic phase transition was investigated by magnetic susceptibility measurements as a function of Ti substitution, revealing a decreasing transition temperature on increasing the level of substitution. The step-like feature in the magnetic susceptibility reflecting the Ru-Ru spin dimerization transition becomes smeared out close to y = 0.3 and completely vanishes at y = 0.45, indicating complete suppression of spin-dimer formation. Additional specific-heat measurements show a continuous decrease of the magnetic entropy peak with increasing Ti substitution mirroring the reduced number of spin dimers due to the magnetic dilution. A magnetic anomaly of the dimerization transition can hardly be detected for y ≥ 0.3. Density functional theory calculations were carried out to study changes of the electronic band structure caused by the substitution. A possibly preferred distribution of Ti and Ru and the magnetic interactions as well as the change of the density of states close to the Fermi level are investigated. Based on these experimental results a detailed (y,T) phase diagram is proposed.
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Affiliation(s)
- S Riegg
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany.
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6
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Tsurkan V, Zherlitsyn S, Yasin S, Felea V, Skourski Y, Deisenhofer J, Krug von Nidda HA, Wosnitza J, Loidl A. Unconventional magnetostructural transition in CoCr2O4 at high magnetic fields. Phys Rev Lett 2013; 110:115502. [PMID: 25166553 DOI: 10.1103/physrevlett.110.115502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Indexed: 06/03/2023]
Abstract
The magnetic-field and temperature dependencies of the ultrasound propagation and magnetization of single-crystalline CoCr(2)O(4) have been studied in static and pulsed magnetic fields up to 14 and 62 T, respectively. Distinct anomalies with significant changes in the sound velocity and attenuation are found in this spinel compound at the onset of long-range incommensurate-spiral-spin order at T(s)=27 K and at the transition from the incommensurate to the commensurate states at T(l)=14 K, evidencing strong spin-lattice coupling. While the magnetization evolves gradually with the field, steplike increments in the ultrasound clearly signal a transition into a new magnetostructural state between 6.2 and 16.5 K and at high magnetic fields. We argue that this is a high-symmetry phase with only the longitudinal component of the magnetization being ordered, while the transverse helical component remains disordered. This phase is metastable in an extended H-T phase space.
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Affiliation(s)
- V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany and Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova
| | - S Zherlitsyn
- Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany
| | - S Yasin
- Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany
| | - V Felea
- Institute of Applied Physics, Academy of Sciences of Moldova, MD 2028 Chisinau, Republic of Moldova
| | - Y Skourski
- Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany
| | - J Deisenhofer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
| | - H-A Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
| | - J Wosnitza
- Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
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7
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Park JT, Friemel G, Li Y, Kim JH, Tsurkan V, Deisenhofer J, Krug von Nidda HA, Loidl A, Ivanov A, Keimer B, Inosov DS. Magnetic resonant mode in the low-energy spin-excitation spectrum of superconducting Rb2Fe4Se5 single crystals. Phys Rev Lett 2011; 107:177005. [PMID: 22107568 DOI: 10.1103/physrevlett.107.177005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Indexed: 05/31/2023]
Abstract
We have studied the low-energy spin-excitation spectrum of the single-crystalline Rb(2)Fe(4)Se(5) superconductor (T(c)=32 K) by means of inelastic neutron scattering. In the superconducting state, we observe a magnetic resonant mode centered at an energy of ℏω(res)=14 meV and at the (0.5 0.25 0.5) wave vector (unfolded Fe-sublattice notation), which differs from the ones characterizing magnetic resonant modes in other iron-based superconductors. Our finding suggests that the 245-iron selenides are unconventional superconductors with a sign-changing order parameter, in which bulk superconductivity coexists with the √5×√5 magnetic superstructure. The estimated ratios of ℏω(res)/k(B)T(c)≈5.1±0.4 and ℏω(res)/2Δ≈0.7±0.1, where Δ is the superconducting gap, indicate moderate pairing strength in this compound, similar to that in optimally doped 1111 and 122 pnictides.
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Affiliation(s)
- J T Park
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
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8
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Tsurkan V, Zherlitsyn S, Felea V, Yasin S, Skourski Y, Deisenhofer J, von Nidda HAK, Lemmens P, Wosnitza J, Loidl A. Magnetostructural transitions in a frustrated magnet at high fields. Phys Rev Lett 2011; 106:247202. [PMID: 21770593 DOI: 10.1103/physrevlett.106.247202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Indexed: 05/31/2023]
Abstract
Ultrasound and magnetization studies of bond-frustrated ZnCr(2)S(4) spinel are performed in static magnetic fields up to 18 T and in pulsed fields up to 62 T. At temperatures below the antiferromagnetic transition at T(N1)≈14 K, the sound velocity as a function of the magnetic field reveals a sequence of steps followed by plateaus indicating a succession of crystallographic structures with constant stiffness. At the same time, the magnetization evolves continuously with a field up to full magnetic polarization without any plateaus in contrast to geometrically frustrated chromium oxide spinels. The observed high-field magnetostructural states are discussed within a H-T phase diagram taking into account the field and temperature evolution of three coexisting spin structures and subsequent lattice transformations induced by the magnetic field.
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Affiliation(s)
- V Tsurkan
- Experimental Physics 5, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Augsburg, Germany
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9
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Eremin MV, Zakharov DV, von Nidda HAK, Eremina RM, Shuvaev A, Pimenov A, Ghigna P, Deisenhofer J, Loidl A. Dynamical Dzyaloshinsky-Moriya interaction in KCuF3. Phys Rev Lett 2008; 101:147601. [PMID: 18851575 DOI: 10.1103/physrevlett.101.147601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Indexed: 05/26/2023]
Abstract
The spin dynamics of the prototypical quasi-one-dimensional antiferromagnetic Heisenberg spin S=1/2 chain KCuF3 is investigated by electron spin resonance spectroscopy. Our analysis shows that the peculiarities of the spin dynamics require a new dynamical form of the antisymmetric anisotropic spin-spin interaction. This dynamical Dzyaloshinsky-Moriya interaction is related to strong oscillations of the bridging fluorine ions perpendicular to the crystallographic c axis. This new mechanism allows us to resolve consistently the controversies in observation of the magnetic and structural properties of this orbitally ordered perovskite compound.
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Affiliation(s)
- M V Eremin
- EP V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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10
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Hemberger J, von Nidda HAK, Tsurkan V, Loidl A. Large magnetostriction and negative thermal expansion in the frustrated antiferromagnet ZnCr2Se4. Phys Rev Lett 2007; 98:147203. [PMID: 17501308 DOI: 10.1103/physrevlett.98.147203] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Indexed: 05/15/2023]
Abstract
A detailed investigation of ZnCr2Se4 is presented which is dominated by strong ferromagnetic exchange but orders antiferromagnetically at TN=21 K. Specific heat and thermal expansion exhibit sharp first-order anomalies at the antiferromagnetic transition. TN is shifted to lower temperatures by external magnetic fields and finally is fully suppressed by a field of 65 kOe. The relative length change DeltaL/L(T) is unusually large and exhibits negative thermal expansion alpha below 75 K down to TN indicating strong frustration of the lattice. Magnetostriction DeltaL/L(H) reveals large values comparable to giant magnetostrictive materials. These results point to a spin-driven origin of the structural instability at TN explained in terms of competing ferromagnetic and antiferromagnetic exchange interactions.
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Affiliation(s)
- J Hemberger
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany
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11
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Hemberger J, Rudolf T, Krug von Nidda HA, Mayr F, Pimenov A, Tsurkan V, Loidl A. Spin-driven phonon splitting in bond-frustrated ZnCr2S4. Phys Rev Lett 2006; 97:087204. [PMID: 17026329 DOI: 10.1103/physrevlett.97.087204] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Indexed: 05/12/2023]
Abstract
Magnetic susceptibility, specific heat, thermal expansion, and IR spectroscopy provide experimental evidence that the two subsequent antiferromagnetic transitions in ZnCr2S4 at TN1 = 15 K and TN2 = 8 K are accompanied by significant thermal and phonon anomalies. The anomaly at TN2 reveals a temperature hysteresis typical for a first-order transformation. Because of strong spin-phonon coupling, both magnetic transitions at TN1 and TN2 induce a splitting of phonon modes. The anomalies and phonon splitting observed at TN2 are suppressed by strong magnetic field. Regarding the small positive Curie-Weiss temperature Theta approximately 8 K, we argue that this scenario of two different magnetic phases with different magnetoelastic couplings results from the strong competition of ferromagnetic and antiferromagnetic exchange.
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Affiliation(s)
- J Hemberger
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany
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12
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Krug von Nidda HA, Kurz T, Loidl A, Hartmann T, Klar PJ, Heimbrodt W, Lampalzer M, Volz K, Stolz W. Tuning the magnetic properties of GaAs:Mn/MnAs hybrids via the MnAs cluster shape. J Phys Condens Matter 2006; 18:6071-6083. [PMID: 21690820 DOI: 10.1088/0953-8984/18/26/025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report a systematic study of ferromagnetic resonance in granular GaAs:Mn/MnAs hybrids grown on GaAs(001) substrates by metal-organic vapour-phase epitaxy. The ferromagnetic resonance of the MnAs clusters can be resolved at all temperatures below T(c). An additional broad absorption is observed below 60 K and is ascribed to localized charge carriers of the GaAs:Mn matrix. The anisotropy of the MnAs ferromagnetic resonance field originates from the magneto-crystalline field and demagnetization effects of the ferromagnetic MnAs clusters embedded in the GaAs:Mn matrix. Its temperature dependence basically scales with magnetization. Comparison of the observed angular dependence of the resonance field with model calculations yields the preferential orientation and shape of the clusters formed in hybrid layers of different thickness (150-1000 nm) grown otherwise at the same growth conditions. The hexagonal axes of the MnAs clusters are oriented along the four cubic GaAs space diagonals. Thin layers contain lens-shaped MnAs clusters close to the surface, whereas thick layers also contain spherical clusters in the bulk of the layer. The magnetic properties of the hexagonal MnAs clusters can be tuned by a controlled variation of the cluster shape.
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Affiliation(s)
- H-A Krug von Nidda
- Experimental Physics V, Elektronic Correlations and Magnetism, Institute for Physics, Augsburg University, 86135 Augsburg, Germany
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13
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Eremin MV, Zakharov DV, Eremina RM, Deisenhofer J, Krug von Nidda HA, Obermeier G, Horn S, Loidl A. Unconventional anisotropic superexchange in alpha'-NaV2O5. Phys Rev Lett 2006; 96:027209. [PMID: 16486630 DOI: 10.1103/physrevlett.96.027209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Indexed: 05/06/2023]
Abstract
The strong line broadening observed in electron spin resonance on NaV2O5 is found to originate from an unusual type of the symmetric anisotropic exchange interaction with simultaneous spin-orbit coupling on both sites. The microscopically derived anisotropic exchange constant is almost 2 orders of magnitude larger than the one obtained from conventional estimations. Based on this result we systematically evaluate the anisotropy of the ESR linewidth in terms of the symmetric anisotropic exchange only, and we find microscopic evidence for precursor effects of the charge ordering already below 150 K.
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Affiliation(s)
- M V Eremin
- EP V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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14
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Deisenhofer J, Braak D, Krug von Nidda HA, Hemberger J, Eremina RM, Ivanshin VA, Balbashov AM, Jug G, Loidl A, Kimura T, Tokura Y. Observation of a griffiths phase in paramagnetic La1-xSrxMnO3. Phys Rev Lett 2005; 95:257202. [PMID: 16384501 DOI: 10.1103/physrevlett.95.257202] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Indexed: 05/05/2023]
Abstract
We report on the discovery of a novel triangular phase regime in the system La1-xSrxMnO3 by means of electron spin resonance and magnetic susceptibility measurements. This phase is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase far above the magnetic ordering temperature. The nature of this phase can be understood in terms of Griffiths singularities arising due to the presence of correlated quenched disorder in the orthorhombic phase.
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Affiliation(s)
- J Deisenhofer
- EP V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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15
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Glazkov VN, Smirnov AI, von Nidda HAK, Loidl A, Uchinokura K, Masuda T. Field-controlled phase separation at the impurity-induced magnetic ordering in the spin-Peierls Magnet CuGeO3. Phys Rev Lett 2005; 94:057205. [PMID: 15783690 DOI: 10.1103/physrevlett.94.057205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Indexed: 05/24/2023]
Abstract
The paramagnetic fraction surviving at the impurity-induced antiferromagnetic phase transition in the spin-Peierls magnet CuGeO3 is found to increase with an external magnetic field. This effect is explained by the competition of the Zeeman interaction and of the exchange interaction of local antiferromagnetic clusters formed on the spin-gap background near impurities.
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Affiliation(s)
- V N Glazkov
- P. L. Kapitza Institute for Physical Problems RAS, 117334 Moscow, Russia.
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16
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Fichtl R, Tsurkan V, Lunkenheimer P, Hemberger J, Fritsch V, von Nidda HAK, Scheidt EW, Loidl A. Orbital freezing and orbital glass state in FeCr2S4. Phys Rev Lett 2005; 94:027601. [PMID: 15698228 DOI: 10.1103/physrevlett.94.027601] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Revised: 10/06/2004] [Indexed: 05/24/2023]
Abstract
Low-temperature specific heat measurements and dielectric spectroscopy have been performed on polycrystalline and single-crystalline FeCr2S4, the single crystals showing a transition into a low-temperature orbital glass phase. The freezing of the orbital moments is revealed by a glasslike specific heat anomaly and by a clear relaxational behavior of the dielectric permittivity, exhibiting several hallmark features of glassy dynamics. The orbital relaxation dynamics continuously slows down over six decades in time, before at the lowest temperatures the glass transition becomes suppressed by quantum tunneling.
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Affiliation(s)
- R Fichtl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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Heinrich M, Krug von Nidda HA, Eremina RM, Loidl A, Helbig C, Obermeier G, Horn S. Spin dynamics and charge order in beta-Na1/3V2O5. Phys Rev Lett 2004; 93:116402. [PMID: 15447361 DOI: 10.1103/physrevlett.93.116402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Indexed: 05/24/2023]
Abstract
We present detailed electron-spin resonance investigations on single crystals of the one-dimensional vanadium-oxide bronze beta-Na(1/3)V2O5. From the angular dependence of the g value it can be concluded that the electrons are primarily located on the V1 zigzag chains. The anisotropy of the linewidth, which is determined by the intrachain symmetric anisotropic exchange interaction, favors statistic electron distribution in the metallic and blockwise charge-order in the insulating phase. The temperature dependence of the linewidth indicates the opening of a charge gap at the metal-to-insulator transition at T(MI)=132 K.
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Affiliation(s)
- M Heinrich
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
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Fritsch V, Hemberger J, Büttgen N, Scheidt EW, Krug von Nidda HA, Loidl A, Tsurkan V. Spin and orbital frustration in MnSc2S4 and FeSc2S4. Phys Rev Lett 2004; 92:116401. [PMID: 15089155 DOI: 10.1103/physrevlett.92.116401] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Indexed: 05/24/2023]
Abstract
Crystal structure, magnetic susceptibility, and specific heat were measured in the normal cubic spinel compounds MnSc2S4 and FeSc2S4. Down to the lowest temperatures, both compounds remain cubic and reveal strong magnetic frustration. Specifically the Fe compound is characterized by a Curie-Weiss (CW) temperature ThetaCW = -45 K and does not show any indications of order down to 50 mK. In addition, the Jahn-Teller ion Fe2+ is orbitally frustrated. Hence, FeSc2S4 belongs to the rare class of spin-orbital liquids. MnSc2S4 is a spin liquid for temperatures T>TN approximately 2 K.
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Affiliation(s)
- V Fritsch
- Experimentalphysik V, Center for Electronic Correlations and Magnetism, Institut für Physik, Universität Augsburg, D-86159 Augsburg, Germany
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Heinrich M, Krug von Nidda HA, Loidl A, Rogado N, Cava RJ. Potential signature of a Kosterlitz-Thouless transition in BaNi2V2O8. Phys Rev Lett 2003; 91:137601. [PMID: 14525336 DOI: 10.1103/physrevlett.91.137601] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Revised: 07/08/2003] [Indexed: 05/24/2023]
Abstract
ESR measurements are reported for the quasi-two-dimensional honeycomb antiferromagnet BaNi2V2O8. Planar anisotropic properties are confirmed by angular dependent investigations of resonance field and linewidth. The divergence of the temperature-dependent linewidth on approaching T(N) from above is described in terms of the Kosterlitz-Thouless transition, the critical behavior close to long-range magnetic order, and the 2D Heisenberg antiferromagnet. We provide arguments that the Kosterlitz-Thouless scenario is compatible with the observed critical exponent and suggest BaNi2V2O8 is a weakly anisotropic 2D Heisenberg antiferromagnet.
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Affiliation(s)
- M Heinrich
- Experimentalphysik V, Elektronische Korrelationen und Magnetismus, Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany
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Hemberger J, Krug von Nidda HA, Fritsch V, Deisenhofer J, Lobina S, Rudolf T, Lunkenheimer P, Lichtenberg F, Loidl A, Bruns D, Büchner B. Evidence for Jahn-Teller distortions at the antiferromagnetic transition in LaTiO3. Phys Rev Lett 2003; 91:066403. [PMID: 12935091 DOI: 10.1103/physrevlett.91.066403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2003] [Indexed: 05/24/2023]
Abstract
LaTiO3 is known as a Mott insulator which orders antiferromagnetically at T(N)=146 K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with measurements of the heat capacity, electrical transport measurements, and optical spectroscopy in untwinned single crystals. At T(N) significant structural changes appear, which are volume conserving. Concomitant anomalies are also observed in the dc resistivity, in bulk modulus, and optical reflectivity spectra. We interpret these experimental observations as evidence of orbital order.
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Affiliation(s)
- J Hemberger
- EKM, Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany
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