1,825 research outputs found
Phase transitions in LuIrSi
We report the results of our investigations on a polycrystalline sample of
LuIrSi which crystallizes in the UCoSi type structure
(Ibam). These investigations comprise powder X-ray diffraction, magnetic
susceptibility, electrical resistivity and high temperature (120-300 K) heat
capacity studies. Our results reveal that the sample undergoes a
superconducting transition below 3.5 K. It also undergoes a first order phase
transition between 150-250 K as revealed by an upturn in the resistivity, a
diasmagnetic drop in the magnetic susceptibility and a large anomaly (20-30
J/mol K) in the specific heat data. We observe a huge thermal hysteresis of
almost 45 K between the cooling and warming data across this high temperature
transition in all our measurements. Low temperature X-ray diffraction
measurements at 87 K reveals that the compound undergoes a structural change at
the high temperature transition. Resistivity data taken in repeated cooling and
warming cycles indicate that at the high temperature transition, the system
goes into a highly metastable state and successive heating/cooling curves are
found to lie above the previous one and the resistance keeps increasing with
every thermal cycle. The room temperature resistance of a thermaly cycled piece
of the sample decays exponentialy with time with a decay time constant
estimated to be about 10 secs. The anomaly (upturn) in the resistivity and
the large drop (almost 45%) in the susceptibility across the high temperature
transition suggest that the observed structural change is accompanied or
induced by an electronic transition.Comment: 7 figures, 1 table and 18 reference
Uplift of Himalaya and it’s implications on the evolution of Indian monsoon
Abstract HKT-ISTP 2013
A
Spin-lattice coupling mediated giant magnetodielectricity across the spin reorientation in Ca2FeCoO5
The structural, phonon, magnetic, dielectric, and magneto dielectric
responses of the pure bulk Brownmillerite compound Ca2FeCoO5 are reported. This
compound showed giant magneto dielectric response (10%-24%) induced by strong
spin-lattice coupling across its spin reorientation transition (150-250 K). The
role of two Debye temperatures pertaining to differently coordinated sites in
the dielectric relaxations is established. The positive giant
magneto-dielectricity is shown to be a direct consequence of the modulations in
the lattice degrees of freedom through applied external field across the spin
reorientation transition. Our study illustrates novel control of
magneto-dielectricity by tuning the spin reorientation transition in a material
that possess strong spin lattice coupling.Comment: 7 pages, 12 figure
Modulated structure in the martensite phase of Ni1.8Pt0.2MnGa: a neutron diffraction study
7M orthorhombic modulated structure in the martensite phase of Ni1.8Pt0.2MnGa
is reported by powder neutron diffraction study, which indicates that it is
likely to exhibit magnetic field induced strain. The change in the unit cell
volume is less than 0.5% between the austenite and martensite phases, as
expected for a volume conserving martensite transformation. The magnetic
structure analysis shows that the magnetic moment in the martensite phase is
higher compared to Ni2MnGa, which is in good agreement with magnetization
measurement
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