M. Ferretti - Univ. Genova, Dip. Chimica e Chimica Fisica, Genova, and INFM Italy

M. Ferretti
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M. Ferretti
Univ. Genova, Dip. Chimica e Chimica Fisica, Genova, and INFM Italy

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Physics - Superconductivity (17)
Physics - Strongly Correlated Electrons (3)
Physics - Materials Science (3)
Nuclear Experiment (1)

Publications Authored By M. Ferretti

The scalar dipole polarizabilities, $\alpha_{E1}$ and $\beta_{M1}$, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry $\Sigma_{3}$ in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. Read More

The possibility of multi-band conductivity and multi-gap superconductivity is explored in oriented V3Si thin films by means of reflectance and transmittance measurements at terahertz frequencies. The temperature dependence of the transmittance spectra in the normal state gives evidence of two bands contributing to the film conductivity. This outcome is consistent with electronic structure calculations performed within density functional theory. Read More

In this paper the magnetic behaviour of undoped and 15% F doped SmFeAsO (Sm-1111) and LaFeAsO (La-1111) samples is presented and discussed. Magnetization measurements are not a simple tool to use for the characterisation of the new family of Fe-based superconductors because magnetic impurities can be easily formed during the preparation procedure and may affect the magnetic signal. In spite of this problem bulk magnetization measurements, properly treated, may give very useful information. Read More

We measure magnetotransport of F doped SmFeAsO samples up to 28T and we extract the upper critical fields, using different criteria. In order to circumvent the problem of criterion-dependence Hc2 values, we suggest a thermodynamic estimation of the upper critical field slope dHc2/dT based on the analysis of conductivity fluctuations in the critical regime. A high field slope as large as -12T/K is thus extracted for the optimally doped sample. Read More

We report measurements of resistivity, magnetoresistivity, Hall effect, Seebeck coefficient, infrared reflectivity of undoped SmFeAsO and lightly doped SmFeAs(O0.93F0.07) oxypnictides. Read More

Oxygen vacancies are introduced in the RuO2 and possibly CuO2 planes of RuSr2GdCu2O8 by annealing in vacuum above 600 K. The diffusive jumps of the O vacancies are accompanied by a reorientation of the local distortion, and are probed by measuring the elastic energy loss and modulus versus temperature at 1-10 kHz. An intense acoustic absorption peak develops near 670 K at 1 kHz and finally stabilizes after heating up to 920 K in vacuum. Read More

A systematic study on the synthesis of the Ru-1212 compound by preparing a series of samples that were annealed at increasing temperatures and then quenched has been performed. It results that the optimal temperature for the annealing lies around 1060-1065 C; a further temperature increase worsens the phase formation. Structural order is very important and the subsequent grinding and annealing improves it. Read More

The evolution of an anelastic relaxation process occurring around 80 K in La{2-x}Sr{x}CuO{4} at a measuring frequency of ~1 kHz has been followed from x = 0.0075 to the overdoped region, x = 0.2, where it disappears. Read More

The anelastic spectra of La$_{2-x}$Sr$_{x}$CuO$_{4}$ have been measured at liquid He temperatures slightly below and above the concentration $% x_{c}\simeq 0.02$ which is considered to separate the spin-glass phase from the cluster spin-glass (CSG) phase. For $x\le x_{c}$ all the elastic energy loss functions show a step below the temperature $T_{g}(x=0. Read More

The complex dynamic Young's modulus of ceramic Nd2-xCexCuO4 with x = 0, 0.05 and 0.20 has been measured from 1. Read More

We report on structural, electrical and magnetic properties of RuSr2GdCu2O8 samples made by systematic synthesis work so that they differ from one onether in number of annealings and sintering temperature. Our aim is to highlight the different behaviours as a consequence of the thermal treatments. In particular, we deal with the onset of superconductivity in relation to the homogenisation process, and its influence on resistivity, structural and magnetic ordering. Read More

We made point-contact measurements with Au tips on La_{2-x}Sr_{x}CuO_{4} samples with 0.08 < x < 0.20 to investigate the relationship between superconducting gap and pseudogap. Read More

The anelastic spectra (elastic energy loss and dynamic modulus versus temperature) of La1-xCaxMnO3 have been measured for 0.33< x < 0.5. Read More

We compare the low frequency (~1 kHz) anelastic spectra of La_{2-x}Sr_xCuO_4 and La_{2-x}Ba_xCuO_4 at x = 0.03 and 0.06 in the temperature region where the freezing into the cluster spin-glass (CSG) phase occurs and is accompanied by an increase of the acoustic absorption. Read More

Affiliations: 1CNR, Ist. Acustica, Roma, and INFM, Italy, 2Univ. di Roma ``La Sapienza``, Dip. Fisica and INFM, Roma, Italy, 3Univ. di Roma ``La Sapienza``, Dip. Fisica and INFM, Roma, Italy, 4Univ. Genova, Dip. Chimica e Chimica Fisica, Genova, and INFM Italy

An increase of the acoustic absorption is found in La_{2-x}Sr_{x}CuO_{4} (x = 0.019, 0.03 and 0. Read More

Affiliations: 1CNR, Ist. Acustica, Roma, and INFM, Italy, 2Univ. di Roma ``La Sapienza``, Dip. Fisica and INFM, Roma, Italy, 3Univ. Genova, Dip. Chimica e Chimica Fisica, Genova, and INFM Italy

The anelastic spectrum of La{2-x}Sr{x}CuO{4} (x = 0, 0.008, 0.019, 0. Read More