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Dive into the research topics where P. P. Kyriakou is active.

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Featured researches published by P. P. Kyriakou.


Physical Review Letters | 2005

Muon spin relaxation studies of magnetic-field-induced effects in high-Tc superconductors

A.T. Savici; A. Fukaya; I. M. Gat-Malureanu; T. Ito; P. L. Russo; Y. J. Uemura; C. R. Wiebe; P. P. Kyriakou; Gregory John MacDougall; M. T. Rovers; G. M. Luke; K. M. Kojima; M. Goto; S. Uchida; Ryosuke Kadono; K. Yamada; S. Tajima; T. Masui; H. Eisaki; N. Kaneko; M. Greven; G. D. Gu

Muon spin relaxation measurements in high transverse magnetic fields [FORMULA: SEE TEXT] revealed strong field-induced quasistatic magnetism in the underdoped and Eu-doped (La,Sr)2CuO4 and La1.875Ba0.125CuO4, existing well above Tc and TN. The susceptibility counterpart of Cu spin polarization, derived from the muon spin relaxation rate, exhibits a divergent behavior towards T approximately 25 K. No field-induced magnetism was detected in overdoped La1.81Sr0.19CuO4, optimally doped Bi2212, and Zn-doped YBa2Cu3O7.


Physical Review Letters | 2003

Superconductivity and field-induced magnetism in Pr2-xCexCuO4 single crystals

J. E. Sonier; K.F. Poon; G. M. Luke; P. P. Kyriakou; R. I. Miller; Ruixing Liang; C. R. Wiebe; P. Fournier; R. L. Greene

We report muon-spin rotation and relaxation (muSR) measurements on single crystals of the electron-doped high-T(c) superconductor Pr2-xCexCuO4. In a zero external magnetic field, superconductivity is found to coexist with dilute Cu spins that are static on the muSR time scale. In an applied field, we observe a mu(+)-Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T(c), an additional source of local magnetic field appears throughout the volume of the sample. This finding is shown to be consistent with field-induced antiferromagnetic ordering of the Cu spins. Measurements of the temperature dependence of the in-plane magnetic penetration depth lambda(ab) in the vortex state are also presented.


Physical Review Letters | 2003

Muon spin relaxation and susceptibility studies of the pure and diluted spin 1/2 kagomé-like lattice system (CuxZn(1-x))3V2O7(OH2) 2H2O.

A. Fukaya; Y. Fudamoto; I.M. Gat; Toshimitsu Ito; M. Larkin; A.T. Savici; Y. J. Uemura; P. P. Kyriakou; G. M. Luke; M. T. Rovers; K. M. Kojima; Amit Keren; M. Hanawa; Zenji Hiroi

Muon spin relaxation and magnetic susceptibility measurements have been performed on the pure and diluted spin 1/2 kagomé system (CuxZn(1-x))3V2O7(OH)2 2H2O. In the pure x=1 system we found a slowing down of Cu spin fluctuations with decreasing temperature towards T approximately 1 K, followed by slow and nearly temperature-independent spin fluctuations persisting down to T=50 mK, indicative of quantum fluctuations. No indication of static spin freezing was detected in either of the pure (x=1.0) or diluted samples. The observed magnitude of fluctuating fields indicates that the slow spin fluctuations represent an intrinsic property of kagomé network rather than impurity spins.


Physica B-condensed Matter | 2003

Spin dynamics in the two-dimensional spin system SrCu2(BO3)2

A. Fukaya; Y. Fudamoto; I.M. Gat; T. Ito; M. Larkin; A.T. Savici; Y. J. Uemura; P. P. Kyriakou; G. M. Luke; M. T. Rovers; Hiroshi Kageyama; Y. Ueda

Abstract Muon spin relaxation measurements have been performed in the two dimensional spin system SrCu2(BO3)2. As the temperature decreases, the relaxation rate increases below T=10 K , and shows a saturation below T=3 K . The line shape at low temperatures is nearly Gaussian, yet it cannot be easily decoupled by an application of longitudinal field. These results indicate the existence of magnetically active spins that show slowing down of fluctuations with decreasing temperatures, yet remain dynamic even at 0.1 K . We have also examined a sample doped with small amount of non-magnetic Zn2+ impurity, Sr(Cu0.99Zn0.01)2(BO3)2. The result was quite similar to the pure sample. Thus, anomalous behavior of the pure sample observed in low temperatures is not due to magnetic moments induced by impurities or a lattice defect.


Physica B-condensed Matter | 2003

Paramagnetic vortex state in Pr2−xCexCuO4 single crystals

J. E. Sonier; K.F. Poon; G. M. Luke; P. P. Kyriakou; R. I. Miller; P. Fournier; R. L. Greene

Abstract Transverse-field muon spin rotation (TF-μSR) measurements of the internal magnetic field distribution of Pr 2− x Ce x CuO 4 single crystals reveal a large increase in the magnitude of the average field in the vortex state under field-cooling conditions. The observed increase in the average internal magnetic field measured by μSR is discussed in the context of the paramagnetic Meissner effect.


Physical Review B | 2003

Frustration-driven spin freezing in the S=½ fcc perovskite Sr2MgReO6

C. R. Wiebe; J.E. Greedan; P. P. Kyriakou; G. M. Luke; J. S. Gardner; A. Fukaya; I. M. Gat-Malureanu; P. L. Russo; Andrei Savici; Y. J. Uemura


Physical Review B | 2004

Two-dimensional nature of superconductivity in the intercalated layered systems LixHfNCl and LixZrNCl: Muon spin relaxation and magnetization measurements

T. Ito; A. Fukaya; I. M. Gat-Malureanu; M. Larkin; P. L. Russo; A.T. Savici; Y. J. Uemura; K. Groves; Ronald Breslow; Ken-ichi Hotehama; Shoji Yamanaka; P. P. Kyriakou; M. T. Rovers; G. M. Luke; Kenji M. Kojima


Physical Review B | 2011

Muon spin relaxation and susceptibility measurements of an itinerant-electron system Sr1−xCaxRuO3: Quantum evolution from ferromagnet to paramagnet

I. M. Gat-Malureanu; J. P. Carlo; Tatsuo Goko; A. Fukaya; Toshimitsu Ito; P. P. Kyriakou; M. Larkin; G. M. Luke; P. L. Russo; Andrei Savici; C. R. Wiebe; Kazuyoshi Yoshimura; Y. J. Uemura


Physical Review Letters | 2003

Field dependence of the muon spin relaxation rate in MnSi.

I. M. Gat-Malureanu; A. Fukaya; M. Larkin; Andrew J. Millis; P. L. Russo; A.T. Savici; Y. J. Uemura; P. P. Kyriakou; G. M. Luke; C. R. Wiebe; Y. V. Sushko; R. H. Heffner; D.E. MacLaughlin; D. Andreica; G. M. Kalvius


Physica C-superconductivity and Its Applications | 2004

Field-induced antiferromagnetic order in Pr2−xCexCuO4

J. E. Sonier; K.F. Poon; G. M. Luke; P. P. Kyriakou; R.I. Miller; R. Liang; C.R. Wiebe; P. Fournier; R. L. Greene

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