5 research outputs found
Structural and magnetic studies of CuO-TeO and CuO-TeO-BO glasses
The glass systems CuO(1)TeO and CuO(1)[ 75TeO
25BO] with 0 < x \leq
50 mol% were investigated by means of X-ray diffraction, electron paramagnetic resonance (EPR) and a.c.
magnetic susceptibility () measurements, the principal aim of the investigation being the
study of the structural modifications in the tellurite glasses introduced by the addition of boron oxide.
In the case of first glass system, i.e. without BO, EPR spectra of Cu ions undergo
changes with the increasing concentration of CuO. At very low concentrations, spectra are due to isolated
Cu ions in axially distorted octahedral sites. The EPR signal for samples with mol% can be explained as being the superposition of two EPR absorptions, one showing the hyperfine
structure typical for isolated Cu ions and the other consisting of a symmetric line typical for
clustered ions. The broadening of the absorption band is due to dipolar as well exchange interaction. The
susceptibility data show that for mol% , the Cu ions are predominantly clustered and are
coupled through antiferromagnetic exchange interaction. A comparative study of amorphous X-ray
diffraction pattern of the glasses indicates a structural modification in the TeO network with
increasing CuO concentration; the effect is quite visible in the samples with CuO concentrations higher
than 20 mole percent. Measurements of density corroborate the conclusions drawn from the X-ray
diffraction. Additionally, we show that our data validates a model in which CuO rich regions are
surrounded by a buffer boundary which separates them from the tellurite glassy network; effect of
introducing BO can be best described as breaking these regions into smaller size regions
Structural and magnetic investigations of the xCuO(100-x)[70TeO2·25B2O3·5SrF2] glasses
Magnetic and electric properties of La<sub>1-δ</sub>MnO<sub>3</sub>
The magnetic phase diagram of powdered samples have
been studied as a function of in the low doping range.
has a canted magnetic structure at low temperature (\theta
\simeq 130\QTR{group}{{}^{\circ}}). Above , it becomes a
paramagnet with a huge effective magnetic moment, ,
reflecting the presence of magnetoelastic polarons which are not affected by
the magnetic field (up to 20T) nor the temperature .
When is increased to , polarons are still presen at
high temperature, with a smaller size: . The system
becomes fully ferromagnetic below 170K but remains insulating down to the
lowest temperature.Comment: 8pages; 6 figures as EPS files adde