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T. Shiroka,
C. Bucci,
R. De Renzi,
F. Galli,
G. Guidi,
G. H. Eaton, P. J. C. King,
C. A. Scott,
K. Träger,
A. Breitrück, [......],
J. Merkel,
P. Neumayer,
I. Reinhard,
R. Santra,
L. Willmann,
V. Meyer,
E. Roduner,
R. Scheuermann,
M. C. Charlton,
P. Donnelly
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ABSTRACT: Standard muon spin rotation (μSR) spectroscopy implants 4 MeV spin-polarized positive muons to investigate the bulk properties
of matter. Success in producing epithermal muons opens interesting possibilities for studying ultrathin films, interfaces,
and even surfaces. At the ISIS Facility, Rutherford Appleton Laboratory (Chilton, UK), we have produced a pulsed ultraslow
muon beam (E< 20 eV) and have performed the first μSR experiments. Due to the pulsed feature, the implantation time is automatically determined
and, by adjusting the final muon energy between about 8 and 20 eV, depth slicing experiments are possible down to monolayers
distances. We describe slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper
oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the
local magnetic field. The results are discussed in relation to the morphological features of the film.
Applied Magnetic Resonance 04/2012; 19(3):471-477. · 0.75 Impact Factor
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J. S. Lord,
I. McKenzie,
P. J. Baker,
S. J. Blundell,
S. P. Cottrell,
S. R. Giblin,
J. Good,
A. D. Hillier,
B. H. Holsman, P. J. C. King,
T. Lancaster,
R. Mitchell,
J. B. Nightingale,
M. Owczarkowski,
S. Poli,
F. L. Pratt,
N. J. Rhodes,
R. Scheuermann,
Z. Salman
[show abstract]
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ABSTRACT: The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.
Review of Scientific Instruments 07/2011; 82(7):073904-073904-10. · 1.37 Impact Factor
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ABSTRACT: In the pyrochlore Yb2GaSbO7, the Yb3 + sublattice forms a network of corner sharing tetrahedra and the second sublattice is made up of disordered, non-magnetic Ga3 + and Sb5 + ions. We have examined this compound using magnetic susceptibility, 170Yb Mössbauer spectroscopy (down to 0.03 K) and muon spin relaxation (μSR) (down to 0.02 K) measurements. We establish the size of the Yb3 + magnetic moments and that of the Yb3 + –Yb3 + coupling. At low temperatures, the correlated moments fluctuate between directions that are well tilted relative to the local [111] axis. The lattice disorder does not quench the frustration induced low temperature spin fluctuations but it does remove the first order dynamic transition that is present in the crystallographically ordered counterpart Yb2Ti2O7. Below 1.0 K, the fluctuation rate of the correlated moments decreases progressively as the temperature is reduced and the moments remain dynamic down to 0.02 K where the rate is 7 × 107 s − 1. Magnetic frustration is operative in Yb2GaSbO7 where the Yb3 + –Yb3 + interaction is antiferromagnetic as it is in Yb2Ti2O7 where the interaction is ferromagnetic.
Journal of Physics Condensed Matter 04/2011; 23(16):164217. · 2.55 Impact Factor
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[show abstract]
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ABSTRACT: In the pyrochlore Yb(2)GaSbO(7), the Yb(3+) sublattice forms a network of corner sharing tetrahedra and the second sublattice is made up of disordered, non-magnetic Ga(3+) and Sb(5+) ions. We have examined this compound using magnetic susceptibility, (170)Yb Mössbauer spectroscopy (down to 0.03 K) and muon spin relaxation (μSR) (down to 0.02 K) measurements. We establish the size of the Yb(3+) magnetic moments and that of the Yb(3+)-Yb(3+) coupling. At low temperatures, the correlated moments fluctuate between directions that are well tilted relative to the local [111] axis. The lattice disorder does not quench the frustration induced low temperature spin fluctuations but it does remove the first order dynamic transition that is present in the crystallographically ordered counterpart Yb(2)Ti(2)O(7). Below 1.0 K, the fluctuation rate of the correlated moments decreases progressively as the temperature is reduced and the moments remain dynamic down to 0.02 K where the rate is 7 × 10(7) s(-1). Magnetic frustration is operative in Yb(2)GaSbO(7) where the Yb(3+)-Yb(3+) interaction is antiferromagnetic as it is in Yb(2)Ti(2)O(7) where the interaction is ferromagnetic.
Journal of Physics Condensed Matter 04/2011; 23(16):164217. · 2.55 Impact Factor
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ABSTRACT: The charge state of muonium has been investigated in p-type doped, nominally undoped (low n-type) and heavily n-type doped InAs. The donor Mu(+) state is shown to be the dominant defect in all cases. Consequently, muonium does not simply counteract the prevailing conductivity in this material. This is consistent with the charge neutrality level lying above the conduction band minimum in InAs.
Journal of Physics Condensed Matter 02/2009; 21(7):075803. · 2.55 Impact Factor
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Physica B Condensed Matter 01/2009; 404:5113-5116. · 1.06 Impact Factor
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Physica B Condensed Matter 01/2009; 404:5117-5120. · 1.06 Impact Factor
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Physica B Condensed Matter 01/2009; 404:812-815. · 1.06 Impact Factor
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ABSTRACT: The detailed dynamics of the positively charged muonium (Mu+) in heavily doped p-type Si:B is reported. Below 200 K, Mu+ is static and isolated, and is located in a stretched Si-Si bond. Above approximately 200 K, Mu+ diffuses incoherently. At temperatures higher than 300 K, the Mu+-B- complex is formed while above 520 K, it starts to dissociate. There is significant enhancement of the diffusion of Mu+ in Si compared to H+ and D+-this is attributed to its smaller mass.
Physical Review Letters 06/2008; 100(25):257602. · 7.37 Impact Factor
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P Dalmas de Réotier,
A Yaouanc,
L Keller,
A Cervellino,
B Roessli,
C Baines,
A Forget,
C Vaju,
P C M Gubbens,
A Amato, P J C King
[show abstract]
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ABSTRACT: We report a study of the geometrically frustrated magnetic material Tb2Sn2O7 by the positive muon-spin relaxation technique. No signature of a static magnetically ordered state is detected while neutron magnetic reflections are observed in agreement with a published report. This is explained by the dynamical nature of the ground state of Tb2Sn2O7: the Tb3+ magnetic moment characteristic fluctuation time is approximately 10(-10) s. The strong effect of the magnetic field on the muon-spin-lattice relaxation rate at low fields indicates a large field-induced increase of the magnetic density of states of the collective excitations at low energy.
Physical Review Letters 04/2006; 96(12):127202. · 7.37 Impact Factor
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ABSTRACT: Specific heat and muon spin rotation and relaxation data are presented for two geometrically frustrated systems: Gd2Ti2O7 which antiferromagnetically orders and Yb2Ti2O7 which presents dynamical short range correlations at low temperature. The muon data help to characterize the spin dynamics of these two compounds. Comment: 6 pages, 5 figures. To be published in the proceedings of the 10th International Conference on Muon Spin Rotation, Relaxation and Resonance, Physica B
12/2005;
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ABSTRACT: From muon spin relaxation spectroscopy experiments, we show that the sharp peak (lambda-type anomaly) detected by specific heat measurements at 54 mK for the ytterbium gallium garnet compound, Yb3Ga5O12, does not correspond to the onset of a magnetic phase transition, but to a pronounced building up of dynamical magnetic pair correlations. Beside the lambda anomaly, a broad hump is observed at higher temperature in the specific heat of this garnet and other geometrically frustrated compounds. Comparing with other frustrated magnetic systems we infer that a ground state with long-range order is reached only when at least 1/4-1/3 of the magnetic entropy is released at the lambda transition.
Physical Review Letters 11/2003; 91(16):167201. · 7.37 Impact Factor
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A. V. Dooglav,
A. V. Egorov,
I. R. Mukhamedshin,
A. V. Savinkov,
H. Alloul,
J. Bobroff,
W. A. MacFarlane,
P. Mendels,
G. Collin,
N. Blanchard,
P. G. Picard, P J C King,
J. Lord
[show abstract]
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ABSTRACT: We present a detailed NQR, NMR and $\mu $SR study of a magnetic phase obtained during a topotactic chemical reaction of YBa$_{2}$Cu$_{3}$O$_{6.5}$ high- temperature superconductor with low-pressure water vapor. Our studies give straightforward evidence that the ''empty'' Cu(1) chains play the role of an easy water insertion channel. It is shown that the NQR spectrum of the starting material transforms progressively under insertion of water, and completely disappears when one H$_{2}$O molecule is inserted per unit cell. Similarly, a Cu ZFNMR signal characteristic of this water inserted material appears and grows with increasing water content, which indicates that the products of the reaction are non-superconducting antiferromagnetic phases in which the bilayers are ordered. These antiferromagnetic phases are felt by proton NMR which reveals two sites with static internal fields of 150 and about 15 Gauss respectively. Two muon sites are also evidenced with similar local fields which vanish at $T\approx 400$ K. This indicates that the magnetic phases have similar N\'{e}el temperatures as the other bilayer undoped compounds. An analysis of the internal fields on different sites of the structure suggests that they can be all assigned to a single magnetic phase at large water content in which the Cu(1) electron spins order with those of the Cu(2). It appears that even samples packed in Stycast epoxy resin heated moderately at a temperature (200$^{0}$C) undergo a reaction with epoxy decomposition products which yield the formation of the same final compound. It is then quite clear that such effects should be considered quite seriously and avoided in experiments attempting to resolve tiny effects in such materials, as those performed in some recent neutron scattering experiments.
10/2003;
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ABSTRACT: Although originally designed by and for the use of the Neutron and X-ray communities, the flexibility of the NeXus data format makes it equally suitable for storing data gathered from MuSR experiments. Furthermore, its use should open up the possibility of sharing software beyond the immediate muon community; giving access to the many tools that are already in existence for manipulating NeXus and HDF based files. This paper explores the development of the NeXus format for storing ISIS muon data and the associated experimental conditions. The design of an Instrument Definition for the ISIS muon instruments is described and the implementation of an application to translate the present ISIS raw data format to the NeXus format presented. The development of a common muon data format is a topic of active discussion within the muon community; with this in mind, the suitability of NeXus and, in particular, the ISIS Instrument Definition for general application is considered. A number of applications that have been developed to exploit the flexibility of the ISIS muon NeXus file format are described and a scheme for enabling web based browsing and analysis of experiment data is introduced.
11/2002;
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J A Hodges,
P Bonville,
A Forget,
A Yaouanc,
P Dalmas de Réotier,
G André,
M Rams,
K Królas,
C Ritter,
P C M Gubbens,
C T Kaiser, P J C King,
C Baines
[show abstract]
[hide abstract]
ABSTRACT: Using neutron diffraction, 170Yb Mössbauer and muon spin relaxation spectroscopies, we have examined the pyrochlore Yb2Ti2O7, where the Yb3+S' = 1/2 ground state has planar anisotropy. Below approximately 0.24 K, the temperature of the known specific-heat lambda transition, there is no long range magnetic order. We show that the transition corresponds to a first-order change in the fluctuation rate of the Yb3+ spins. Above the transition temperature, the rate, in the GHz range, follows a thermal excitation law, whereas below, the rate, in the MHz range, is temperature independent, indicative of a quantum fluctuation regime.
Physical Review Letters 03/2002; 88(7):077204. · 7.37 Impact Factor
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Physical Review Letters 01/1999; 83:4405. · 7.37 Impact Factor
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