R. F. Kiefl
University of British Columbia
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Featured researches published by R. F. Kiefl.
Physical Review Letters | 2002
R. I. Miller; R. F. Kiefl; J. H. Brewer; J. E. Sonier; J. Chakhalian; S. R. Dunsiger; G. D. Morris; A.N. Price; D. A. Bonn; Hardy Wh; R. Liang
Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories.
Physical Review Letters | 1999
J. E. Sonier; J. H. Brewer; R. F. Kiefl; Gerald D. Morris; R. I. Miller; D. A. Bonn; J. Chakhalian; R. H. Heffner; W. N. Hardy; R. Liang
A novel high magnetic field (8 T) spectrometer for muon spin rotation has been used to measure the temperature dependence of the in-plane magnetic penetration depth {lambda}{sub ab} in YBa{sub 2}Cu {sub 3}O{sub 6.95} . At low H and low T , {lambda}{sub ab} exhibits the characteristic linear T dependence associated with the energy gap of a d{sub x{sup 2}-y{sup 2}}-wave superconductor. However, at higher fields {lambda}{sub ab} is essentially temperature independent at low T . We discuss possible interpretations of this surprising new feature in the low-energy excitation spectrum. (c) 1999 The American Physical Society.
Nano Letters | 2007
Z. Salman; K. H. Chow; R. I. Miller; Andrea Morello; T. J. Parolin; M.D. Hossain; T. A. Keeler; C. D. P. Levy; W.A. MacFarlane; G. D. Morris; H. Saadaoui; D. Wang; Roberta Sessoli; G. G. Condorelli; R. F. Kiefl
The magnetic properties of a monolayer of Mn12 single molecule magnets grafted onto a silicon (Si) substrate have been investigated using depth-controlled beta-detected nuclear magnetic resonance. A low-energy beam of spin-polarized radioactive 8Li was used to probe the local static magnetic field distribution near the Mn12 monolayer in the Si substrate. The resonance line width varies strongly as a function of implantation depth as a result of the magnetic dipolar fields generated by the Mn12 electronic magnetic moments. The temperature dependence of the line width indicates that the magnetic properties of the Mn12 moments in this low-dimensional configuration differ from bulk Mn12.
Physical Review Letters | 2012
Z. Salman; Oren Ofer; M. Radovic; H. Hao; M. Ben Shalom; K. H. Chow; Y. Dagan; M.D. Hossain; C. D. P. Levy; W.A. MacFarlane; G. M. Morris; L. Patthey; M. R. Pearson; H. Saadaoui; T. Schmitt; Denan Wang; R. F. Kiefl
We report the observation of weak magnetism in superlattices of LaAlO(3)/SrTiO(3) using β-detected nuclear magnetic resonance. The spin lattice relaxation rate of ^{8}Li in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO(3) exhibits a strong peak near ~35 K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO(3)/SrTiO(3) interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of ~4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (~0.002μ(B)) in the two samples with a larger LaAlO(3) spacer thickness.
Physical Review Letters | 2006
Z. Salman; R. F. Kiefl; K. H. Chow; M.D. Hossain; T. A. Keeler; S. R. Kreitzman; C. D. P. Levy; R. I. Miller; T. J. Parolin; M. R. Pearson; H. Saadaoui; J. D. Schultz; M. Smadella; Denan Wang; W.A. MacFarlane
We demonstrate that zero-field beta-detected nuclear quadrupole resonance and spin relaxation of low energy (8)Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO(3) single crystal occurs at T(c) approximately 150K, i.e., approximately 45K higher than T(c)bulk, and that the tetragonal domains formed below T(c) are randomly oriented.
Physical Review Letters | 1997
J. E. Sonier; R. F. Kiefl; J. H. Brewer; J. Chakhalian; S. R. Dunsiger; W.A. MacFarlane; R. I. Miller; A. Wong; G. M. Luke; J.W. Brill
Muon-spin rotation spectroscopy ({mu}SR) has been used to measure the internal magnetic field distribution in NbSe{sub 2} for H{sub c1}{lt}H{lt}0.25H{sub c2} . The deduced profiles of the supercurrent density J{sub s} indicate that the vortex-core radius {rho}{sub 0} in the bulk decreases sharply with increasing magnetic field. This effect, which is attributed to increased vortex-vortex interactions, does not agree with the dirty-limit microscopic theory. A simple phenomenological equation in which {rho}{sub 0} depends on the intervortex spacing is used to model this behavior. In addition, we find for the first time that the in-plane magnetic penetration depth {lambda}{sub ab} increases linearly with H in the vortex state of a conventional superconductor. {copyright} {ital 1997} {ital The American Physical Society}
Physical Review Letters | 2007
Z. Salman; Denan Wang; K. H. Chow; Hossain; Kreitzman; T. A. Keeler; C. D. P. Levy; W.A. MacFarlane; R. I. Miller; G. D. Morris; T. J. Parolin; H. Saadaoui; M. Smadella; R. F. Kiefl
A low energy radioactive beam of polarized
Physical Review Letters | 1997
J. E. Sonier; J. H. Brewer; R. F. Kiefl; D. A. Bonn; S. R. Dunsiger; W. N. Hardy; Ruixing Liang; W.A. MacFarlane; R. I. Miller; T. M. Riseman; D. R. Noakes; C. E. Stronach; M.F. White
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Physical Review B | 2007
Z. Salman; A. I. Mansour; K. H. Chow; M. Beaudoin; I. Fan; J. Jung; T. A. Keeler; R. F. Kiefl; C. D. P. Levy; R. C. Ma; G. D. Morris; T. J. Parolin; Denan Wang; W.A. MacFarlane
Li has been used to observe the vortex lattice near the surface of superconducting NbSe
Physical Review B | 2002
J. E. Sonier; J. H. Brewer; R. F. Kiefl; R. H. Heffner; K. F. Poon; S. L. Stubbs; G. D. Morris; R. I. Miller; W. N. Hardy; R. Liang; D. A. Bonn; J. S. Gardner; C. E. Stronach; N. J. Curro
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