F. Cordero

Glassy dynamics of the inhomogeneous metallic phase in La 1 − x Ca x MnO 3

The anelastic spectra (elastic energy loss and dynamic modulus versus temperature) of La 1 - x Ca x MnO 3 have been measured for 0.33<x<0.5. A peak in the imaginary part of the elastic susceptibility is found slightly belowthe Curie temperature, whose temperature and frequency dependences are typical of the dielectric and magnetic susceptibilities of relaxor ferroelectrics, spin glasses and other inhomogeneous frustrated systems. The fluctuations can be associated with the magnetic clusters which are observed by several techniques or with charge-ordered insulating domains in the low temperature inhomogeneous phase. The temperature dependent distribution function of the fluctuation energy barriers has been extracted by an analysis of the experimental curves.

Mechanisms of the semi-insulating conversion of InP by anelastic spectroscopy

Venezia Tecnologie SpA (ENI Group), Via delle Industrie 39, I-30175 P. Marghera (VE), Italy~Received 2 December 1999!Elastic energy absorption measurements versus temperature on semiconducting, semi-insulating~SI!, andFe-doped InP are reported. A thermally activated relaxation process is found only in the SI state, which isidentified with the hopping of H atoms trapped at In vacancies. It is proposed that the presence of In vacanciesin InP prepared by the liquid encapsulated Czochralski method is due to the lowering of their energy by thesaturation of the P dangling bonds with H atoms dissolved from the capping liquid containing H

Pinning of the domain walls of the cluster spin-glass phase in the low-temperature-tetragonal phase of La2¿xBaxCuO4

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. The dependence of the amplitude of the anelastic relaxation on doping is explained in terms of movement of the domain walls (DW) in the CSG phase between the Sr (Ba) pinning points. The LBCO sample at x = 0.06 transforms into the LTT structure below 40 K and the amplitude of the anelastic anomaly is 7 times smaller than expected, indicating pinning of the DW which run parallel to the LTT modulation. Such DW can be identified with the stripes of high hole density, and the present measurements show that they are mobile between the Sr (Ba) pinning points down to few kelvin, but become static in the presence of LTT modulation also far from the condition x = 1/8 for commensurability between stripe and lattice periodicities.

Anelastic spectroscopy study of the spin-glass and cluster spin-glass phases of La 2 − x Sr x CuO 4 ( 0.015 x 0.03 )

The anelastic spectra of

Cluster spin-glass distribution functions inLa2−xSrxCuO4

{\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}

Tunneling-driven tilt modes of the O octahedra in La 2 − x Sr x CuO 4 : Strong dependence on doping

have been measured at liquid-He temperatures slightly below and above the concentration

Anelastic spectroscopy study of very diluted Zr–D tunnel systems in Nb single crystals

{x}_{c}\ensuremath{\simeq}0.02,

Tunneling of H within nearly undistorted substitutional-H pairs in Nb: a centrosymmetric four-level system

which is considered to separate the spin-glass phase from the cluster spin-glass (CSG) phase. For

DYNAMICS OF THE LOW TEMPERATURE GLASS-LIKE PHASE IN MANGANITES

xl~{x}_{c},

ANELASTIC SPECTROSCOPY AND NQR RELAXATION IN Sr-DOPEN La2CuO4 AROUND THE AF PERCOLATION THRESHOLD

all the elastic energy-loss functions show a step below the temperature