R. Tedeschi

Effects of oxygen stoichiometry on the copper NMR and NQR in YBa2Cu3O7−y

Abstract We present Cu NMR and NQR measurements performed in the normal phase on YBa 2 Cu 3 O 7− y samples of different oxygen content. An attribution of the signals to the inequivalent copper sites in the lattice, and the charge distribution around these ions are discussed.

Relation between Tc and London penetration depth in YBa2(Cu1−xZnx)3O7 by μSR

Abstract We report on NQR and μSR experiments on YBa 2 (Cu 1− x Zn x ) 3 O 7 aimed at investigating the role of carrier effective mass in determining T c . Our findings indicate Zn localization in Cu planes and a nonlinear dependence of T c on the ratio m ∗ c / m ∗ ab .

Study of the plastic phases of norbornene and bicyclooctene by means of muonic radicals

We have observed the formation of muonium adduct radicals in norbornene and bicyclooctene. The behavior of the hyperfine constants and of the μSR linewidths have been investigated as a function of temperature; they have been correlated with the reorientational dynamics of the molecules, which have already been partially determined by means of Raman, NMR, and neutron scattering data. Our measurements have also been interpreted in terms of the electronic configuration of the radicals. In the case of norbornene at the plastic–brittle transition, an abrupt change of τc of 13 orders of magnitude was determined.

Muon spin rotation evidence for a glassy superconducting state in YBa2Cu3O7-y

Abstract We report on muon spin rotation (μSR) measurements of the internal magnetization in polycrystalline samples of the high T c superconductor YBa 2 Cu 3 O 7- y . The mean value as well as the mean square deviation of the internal magnetic field seen by the muons undergo large variations with temperature. This effect shows a marked dependence on the magnetic history of the sample, which is what is expected of a glassy superconducting state.

NQR characterization of Bi2Sr2Can−1CunO4+2n materials

Abstract We performed copper and bismuth NQR on samples of the Bi 2 Sr 2 Ca n−1 Cu n O 4+2n structure, with n =2,3, obtained by varying the ratio between Sr and Ca, or by partially substituting Bi by Pb. The NQR spectra properties have been correlated to the observed features of the X-ray powder diffraction patterns and to the onset of superconductivity. Local dishomogeneities associated with the well known superstructures, typical of the Bisco compounds, have been identified, both in the copper and in the bismuth layers, in all samples, irrespective of the number of CuO 2 planes present.

Interaction of muonium with molecules of biological interest in water solution

Muoniums reaction constants with DNA and its constituents in water solutions are reported and compared with the available data for hydrogen. The low frequency spectrum of the resulting muonic radicals in low magnetic fields is recognized.

The magnetic phase in 2-2-1-2 superconducting materials

Three related aspects of the magnetic phase diagram are presented here: the first deals with the disruption of the antiferromagnetic order in the electron rich phase obtained by Ce doping, the second concern the role of Bi planes as a sink-buffer of carriers, the third focuses the magnetization vs. temperature curves in a variety of different bilayer materials as seen by the muons and discusses the “anomalous” behaviour in relation to theoretical predictions and neutron scattering data.

Muon localization and hyperfine fields in simple antiferromagnets MnF2 and CoF2

Muons implanted in MnF2 and CoF2 are localized at low temperatures in an interstitial site which exhibits octahedral symmetry. Measurements of the critical damping close toTN and the hyperfine field in the AF phase are reported.

Study of the depression of superconductivity by Pr in YBa2Cu3O7

Abstract Penetrations depth is measured in Y 1− x Pr x Ba 2 Cu 3 O 7 oriented powders by Muon Spin Rotation. The observed anisotropy in the effective mass tensor and the relation between T c and the carrier density confirms the hole-filling mechanism.

On the Phase Diagram of Bismuth Based Superconductors

μSR has proven an ideal tool to probe magnetic ordering, thanks to the fact that muons can be implanted in virtually any compound and that they can most often be considered passive probes of the intrinsic behaviour of their hosts. In the study which we present here we have addressed the issue of characterizing the basic magnetic properties of the 2-2-1-2 materials of the family of the Bi2Sr2CaCu2O8 superconductor. The primary aim of this work is to ascertain the analogies between this and the other generations of high Tc materials (in particular La2-xSrxCuO4 and YBa2Cu3O7-y).