17 research outputs found
Three terminal capacitance technique for magnetostriction and thermal expansion measurements
An instrument has been constructed to measure a large range of
magnetostriction and thermal expansion between room temperature and 4 K in a
superconductive split-coil magnet, that allows investigation in magnetic fields
up to 12 T. The very small bulk samples (up to 1 mm in size) as well as big
ones (up to 13 mm) of the irregular form can be measured. The possibility of
magnetostriction investigation in thin films is shown. A general account is
given of both electrical and the mechanical aspects of the design of
capacitance cell and their associated electronic circuitry. A simple lever
device is proposed to increase the sensitivity twice. The resulting obtained
sensitivity can be 0.5 Angstrom. The performance of the technique is
illustrated by some preliminary measurements of the magnetostriction of
superconducting MgB2, thermal expansion of (La0.8Ba0.2)0.93MnO3 single crystal
and magnetoelastic behavior of the Ni/Si(111) and
La0.7Sr0.3CoO3/SAT0.7CAT0.1LA0.2(001) cantilevers.Comment: 6 pages, 6 figures, journal pape
Magnetostrictive behaviour of thin superconducting disks
Flux-pinning-induced stress and strain distributions in a thin disk
superconductor in a perpendicular magnetic field is analyzed. We calculate the
body forces, solve the magneto-elastic problem and derive formulas for all
stress and strain components, including the magnetostriction . The
flux and current density profiles in the disk are assumed to follow the Bean
model. During a cycle of the applied field the maximum tensile stress is found
to occur approximately midway between the maximum field and the remanent state.
An effective relationship between this overall maximum stress and the peak
field is found.Comment: 8 pages, 6 figures, submitted to Supercond. Sci. Technol., Proceed.
of MEM03 in Kyot
Shape Distortion by Irreversible Flux-Pinning-Induced Magnetostriction
Exact analytical results are obtained for the flux-pinning-induced
magnetostriction in cylindrical type-II superconductors placed in parallel
magnetic field. New modes of irreversible deformation are found: In contrast to
the circular cylinder where shape is conserved, it is shown that a square
cross-section deforms with considerable distortion. During a field cycle both
concave, convex, and even more complicated distortions are predicted. Strong
implications for dilatometric measurements on crystals are emphasized. The main
results are valid for any critical-state model, j_c = j_c(B).Comment: 4 pages, 4 graph
Time evolution of the magnetic properties of la0.5R0.5Ba2Cu3O6+x(R = rare earth) high-Tc superconductors
The magnetic properties of the mixed high-Tc superconductors Ea0.5R0.5Ba2Cu3O6+x (R - rare earth) are studied after prolonged 'aging' at room temperature (RT) for 1 year. Enhancement of the superconducting properties comprising the increase of the inhomogeneous diamagnetic signal for members of the series with the larger R-ion radius is detected after RT 'aging'. For the members with the larger R-ion radius the diamagnetic signal has been come more stronger whereas for the members with the smaller R-ion radius the time evolution of the superconducting properties remained almost the unchanged and the diamagnetic signal slightly decreases after 'aging'. The growth of the EPR intensity of localized Cu2+ centers complying with the rise of the normal-state magnetic susceptibility after prolonged storage at RT, is detected. The time evolution effects are related to slow ion diffusion processes that can be induced by stress-relaxation in the mixed Ea0.5R0.5Ba2Cu3O6+x structure, most pronounced for large R-ion radius. © 1999 Elsevier Science B.V. All rights reserved
Time evolution of copper defects in the mixed phase La0.5Gd0.5Ba2Cu3Oy
XRD, magnetic and EPR studies of the mixed phase La0.5Gd0.5Ba2Cu3Oy high-Tc superconductor after prolonged (one year) `aging' at room temperature are reported. Within this time period a pronounced change of the superconducting behavior and the homogeneity of the diamagnetic shielding signal accompanied by substantial structural changes, reduction of the impurity phase BaCuO2+x and increase of the EPR spectrum's intensity of Cu2+ magnetic defects is detected. The `aging' effects are related to strain-relaxation taking place during room temperature annealing that induces the formation of Cu2+ defect centers
Magnetostriction studies in nano-crystalline zinc ferrite thin films by strain modulated ferromagnetic resonance
The magnetoelastic properties of nano-crystalline zinc ferrite (ZnFe2O4) thin films prepared by Pulse laser deposition on amorphous fused quartz substrates have been investigated by means of the strain-modulated ferromagnetic resonance, as a function of the substrate temperature during the deposition, and as a function of the annealing temperature. Magnetoelastic constants reveal the same trends as the magnetization, showing correlation between these two parameters. The results are similar to that obtained earlier for the Y3Fe5O12 ferrite. (C) 2018 Elsevier B.V. All rights reserved