221 research outputs found
Local Atomic Structure of Martensitic NiMnGa: An EXAFS Study
The local atomic structure of NiMnGa with 0
0.16 alloys was explored using Mn and Ga K-edge Extended X-ray Absorption Fine
Structure (EXAFS) measurement. Inorder to study the atomic re-arrangements that
occur upon martensitic transformation, room temperature and low temperature
EXAFS were recorded. The changes occurring in the L2 unit cell and the bond
lengths obtained from the analysis enables us to determine the modulation
amplitudes over which the constituent atoms move giving rise to shuffling of
the atomic planes in the modulated structure. The EXAFS analysis also suggests
the changes in hybridization of Ga- and Ni- orbitals associated with the
local symmetry breaking upon undergoing martensitic transition.Comment: Accepted for publication in Physical Review
Local atomic arrangement and martensitic transformation in NiMnIn: An EXAFS Study
Heusler alloys that undergo martensitic transformation in ferromagnetic state
are of increasing scientific and technological interest. These alloys show
large magnetic field induced strains upon martensitic phase change thus making
it a potential candidate for magneto-mechanical actuation. The crystal
structure of martensite is an important factor that affects both the magnetic
anisotropy and mechanical properties of such materials. Moreover, the local
chemical arrangement of constituent atoms is vital in determining the overall
physical properties. NiMnIn is one such ferromagnetic
shape memory alloy that displays exotic properties like large magnetoresistance
at moderate field values. In this work, we present the extended x-ray
absorption fine-structure measurements (EXAFS) on the bulk
NiMnIn which reveal the local structural change that
occurs upon phase transformation. The change in the bond lengths between
different atomic species helps in understanding the type of hybridization which
is an important factor in driving such Ni-Mn based systems towards martensitic
transformation
Effect of Oxygen Content on Magnetic Properties of Layered Cobaltites PrBaCo2O5+\delta
The effect of oxygen content on the magnetic properties of the layered
perovskites has been investigated. The samples, PrBaCoO
(0.35 0.80) were prepared by sol-gel method and
characterized by X-ray diffraction and DC magnetization. A detailed magnetic
phase diagram for PrBaCoO is presented. It is found that
unlike in the case of heavier rare-earths, ferromagnetic interactions are
present at all temperatures below Tc and even in the antiferromagnetically
ordered phase. Moreover, in compounds with lower oxygen content, short range
ferromagnetic interactions are present even above Tc. This dependence of
magnetic properties on oxygen content in these layered perovskites has been
linked to the changes in polyhedra around the Co ions.Comment: 20 pages, 10 figures; J. Appl. Phys. vol. 110 issue 5 (2011
Inelastic Neutron scattering in CeSi_{2-x}Ga_x ferromagnetic Kondo lattice compounds
Inelastic neutron scattering investigation on ferromagnetic Kondo lattice
compounds belonging to CeSi_{2-x}Ga_{x}, x = 0.7, 1.0 and 1.3, system is
reported. The thermal evolution of the quasielastic response shows that the
Kondo interactions dominate over the RKKY interactions with increase in Ga
concentration from 0.7 to 1.3. This is related to the increase in k-f
hybridization with increasing Ga concentration. The high energy response
indicates the ground state to be split by crystal field in all three compounds.
Using the experimental results we have calculated the crystal field parameters
in all three compounds studied here.Comment: 12 Pages Revtex, 2 eps figures
Chemical ordering in As-Se glasses: X-ray absorption edge and XPES studies
X-ray absorption edge and X-ray photoelectron spectroscopic studies of As-Se glasses seem to support a chemical ordering model
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