F. La Mattina
University of Zurich
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Publication
Featured researches published by F. La Mattina.
Ibm Journal of Research and Development | 2008
S. F. Karg; G. I. Meijer; J. G. Bednorz; C. T. Rettner; Alejandro G. Schrott; E. A. Joseph; Chung Hon Lam; M. Janousch; U. Staub; F. La Mattina; Santos F. Alvarado; D. Widmer; Richard Stutz; Ute Drechsler; D. Caimi
We provide a status report on the development of perovskite-based transition-metal-oxide resistance-change memories. We focus on bipolar resistance switching observed in Cr-doped SrTiO3 memory cells with dimensions ranging from bulk single crystals to CMOS integrated nanoscale devices. We also discuss electronic and ionic processes during electroforming and resistance switching, as evidenced from electron-parametric resonance (EPR), x-ray absorption spectroscopy, electroluminescence spectroscopy, thermal imaging, and transport experiments. EPR in combination with electroluminescence reveals electron trapping and detrapping processes at the Cr site. Results of x-ray absorption experiments prove that the microscopic origin of the electroforming, that is, the insulator-to-metal transition, is the creation of oxygen vacancies. Cr-doped SrTiO3 memory cells exhibit short programming times (≤100 ns) and low programming currents (<100 µA) with up to 105 write and erase cycles.
Physical Review Letters | 2007
R. Khasanov; A. Shengelaya; A. Maisuradze; F. La Mattina; Annette Bussmann-Holder; H. Keller; K. Müller
The in-plane magnetic field penetration depth (\lambda_{ab}) in single-crystal La_{1.83}Sr_{0.17}CuO_4 was investigated by means of the muon-spin rotation (\muSR) technique. The temperature dependence of \lambda^{-2}_{ab} has an inflection point around 10-15K, suggesting the presence of two superconducting gaps: a large gap (\Delta_1^d) with d-wave and a small gap (\Delta_2^s) with s-wave symmetry. The zero-temperature values of the gaps at \mu_0H=0.02T were found to be \Delta_1^d(0)=8.2(2)meV and \Delta_2^s(0)=1.57(8)meV.
Applied Physics Letters | 2008
F. La Mattina; J. G. Bednorz; Santos F. Alvarado; A. Shengelaya; H. Keller
An insulator-to-metal transition is observed in Cr-doped SrTiO3 single crystals upon extended exposure to a high electric field, namely, electroconditioning (EC). Electron paramagnetic resonance (EPR) and transport measurements under laser irradiation show anticorrelation between the Cr3+ EPR signal and the electrical current. This proves that the Cr3+ ions are responsible for the photocurrent that initiates the EC process. We observe the presence of Cr3+∕Cr4+ mixed valencies in the bulk in the conducting state. The EPR characterization of the spectra in the conducting state excludes the possibility of a Cr3+-oxygen vacancy complex in the bulk as a result of the EC.
EPL | 2007
Annette Bussmann-Holder; R. Khasanov; A. Shengelaya; A. Maisuradze; F. La Mattina; H. Keller; K. Müller
The recent observation of an inflection point in the temperature dependence of the in-plane magnetic field dependence (λab) is investigated within a two-band model with coupled order parameters of different symmetries. While the dominant order parameter has d-wave symmetry, the smaller one is of s-wave symmetry. Superconductivity is robust in the d-wave channel and induced via interband interactions in the s-wave subsystem.
Physical Review Letters | 2004
R. Khasanov; D. G. Eshchenko; J. Karpinski; S. M. Kazakov; N. D. Zhigadlo; R. Brütsch; D. Gavillet; D. Di Castro; A. Shengelaya; F. La Mattina; A. Maisuradze; C. Baines; H. Keller
Magnetization measurements under hydrostatic pressure up to 8 kbar in the pyrochlore superconductor RbOs2O6 (T(c) approximately or equal 6.3 K at p=0) were carried out. A positive pressure effect on T(c) with dT(c)/dp=0.090(3) K/kbar was observed, whereas no pressure effect on the magnetic penetration depth lambda was detected. The pressure independent ratio 2 Delta(0)/k(B)T(c)=3.72(2) (Delta(0) is the superconducting gap at zero temperature) was found to be close to the BCS value 3.52. Magnetization and muon-spin rotation measurements of lambda(T) indicate that RbOs2O6 is an adiabatic s-wave BCS-type superconductor. The value of lambda extrapolated to zero temperature and ambient pressure was estimated to be 230(30) nm.
Physical Review B | 2006
R. Khasanov; I. L. Landau; C. Baines; F. La Mattina; A. Maisuradze; Kazumasa Togano; H. Keller
Measurements of the magnetic field penetration depth
Physical Review B | 2005
R. Khasanov; D. G. Eshchenko; D. Di Castro; A. Shengelaya; F. La Mattina; A. Maisuradze; C. Baines; H. Luetkens; J. Karpinski; S. M. Kazakov; H. Keller
\lambda
Physical Review B | 2006
R. Khasanov; I. L. Landau; C. Baines; F. La Mattina; A. Maisuradze; Kazumasa Togano; H. Keller
in the ternary boride superconductor Li
Physical Review B | 2006
R. Khasanov; I. L. Landau; C. Baines; F. La Mattina; A. Maisuradze; Kazumasa Togano; H. Keller
_2
Applied Physics A | 2007
Santos F. Alvarado; F. La Mattina; J. G. Bednorz
Pd