404 research outputs found
Superconductivity at 5.2 K in ZrTe3 polycrystals and the effect of Cu, Ag intercalation
We report the occurrence of superconductivity in polycrystalline samples of
ZrTe3 at 5.2 K temperature at ambient pressure. The superconducting state
coexists with the charge density wave (CDW) phase, which sets in at 63K. The
intercalation of Cu or Ag, does not have any bearing on the superconducting
transition temperature but suppresses the CDW state. The feature of CDW anomaly
in these compounds is clearly seen in the DC magnetization data. Resistivity
data is analysed to estimate the relative loss of carriers and reduction in the
nested Fermi surface area upon CDW formation in the ZrTe3 and the intercalated
compounds.Comment: 5 pages, 8 figure
Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics
Results of low temperature magnetoresistance () and
isothermal magnetization (M) measurements on polycrystalline ferromagnetic (T_C
close to 300 K) natural multilayers, LaMn_{2+x}Ge_{2-y}Si_y, are reported. It
is found that the samples with large residual resistivity ratio,
, exhibit large positive magnetoresistance at high
magnetic fields. The Kohler's rule is not obeyed in these alloys. In addition,
at 4.5 K, there is a tendency towards linear variation of
with magnetic field with increasing ); however, the field
dependence of does not track that of M, thereby suggesting
that the magnetoresistance originates from non-magnetic layers. It is
interesting that these experimental findings on bulk polycrystals are
qualitatively similar to what is seen in artificially grown multilayer systems
recently.Comment: 5 pages, 3 figures, separate figures. This work is a follow-up of our
earlier paper in APL, Ref. : APL Vol 71, pp 2385 (1997
An insight into spin-chain magnetism through Moessbauer spectroscopic investigations in Eu-doped Ca3Co2O6 and Ca3CoRhO6
We report the results of 151Eu Moessbauer effect and magnetization
measurements in the Eu-doped Ca3Co2O6 and Ca3CoRhO6, which are of great current
interest in the fields of spin-chain magnetism and geometrical frustration. We
find that there is a pronounced increase in the line-width of the Moessbauer
spectra below a certain characteristic temperature which is well-above the one
at which three-diensional ordering features set in. This unusual broadening of
the spectra indicates the existence of a characteristic temperature in these
'exotic' magnetic systems, attributable to the onset of incipient
one-dimensional magnetic order. This is inferred from an intriguing correlation
of this characteristic temperature with the paramagnetic Curie temperature (a
measure of intrachain coupling strength in these cases)
Transport and magnetic anomalies due to A-site ionic size mismatch in LaCaBa_{x}MnO
We present results of electrical resistivity, magnetoresistance and ac and dc
magnetic susceptibility on polycrystalline samples of the type
La(0.5)Ca(0.5-x)Ba(x)MnO(3) synthesized under identical heat treatment
conditions. The substitution of larger Ba ions for Ca results in a non-
monotonic variation of the curie temperature as the system evolves from a
charge ordered insulating state for x=0 to a ferromagnetic metallic state for
x=0.5. An intermediate compositino, x=0.1, interestingly exhibits
ferromagnetic. insulating behaviour with thermal hysteresis in ac chi around
the curie tem- perature (120K). The x=0.2 and 0.3 compounds exhibit
semiconducting like behavior as the temperature is lowered below 300K, with a
broad peak in rho around 80-100K: These compositions exhibit a weak increase in
rho as the temperature lowered below 30K, indicative of electron localization
effects. These compositions also undergo ferromagnetic transitions below about
200 and 235K respectively, though these are non-hysteretic; above all, for
these compositions, MR is large and conveniently measurable over the entire
tempera- ture range of measurement below Tc. This experimental finding may be
of interest from the application point of view. We infer that the A-site
ionic-size mismatch plays a crucial role in the deciding these properties.Comment: 5 pages, 6 Figures, Resubmitted with extended abstract on 26 Nov,
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