182 research outputs found
Magnetic-crystallographic phase diagram of superconducting parent compound FeTe
hrough neutron diffraction experiments, including spin-polarized
measurements, we find a collinear incommensurate spin-density wave with
propagation vector () at base
temperature in the superconducting parent compound FeTe. This critical
concentration of interstitial iron corresponds to and leads
crystallographic phase separation at base temperature. The spin-density wave is
short-range ordered with a correlation length of 22(3) \AA, and as the ordering
temperature is approached its propagation vector decreases linearly in the
H-direction and becomes long-range ordered. Upon further populating the
interstitial iron site, the spin-density wave gives way to an incommensurate
helical ordering with propagation vector () at base temperature. For a sample with , we
also find an incommensurate spin-density wave that competes with the
bicollinear commensurate ordering close to the N\'eel point. The shifting of
spectral weight between competing magnetic orderings observed in several
samples is supporting evidence for the phase separation being electronic in
nature, and hence leads to crystallographic phase separation around the
critical interstitial iron concentration of 12%. With results from both powder
and single crystal samples, we construct a magnetic-crystallographic phase
diagram of FeTe for $ 5% < x <17%
Structure and magnetic properties of the amorphous Co80Si9B11 alloy
Purpose: The main aim of the paper was to study the influence of heat treatment on changes of structure and magnetic properties of the amorphous Co80Si9B11 alloy.Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe), static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).Findings: The crystallization process involved by heat treatment leads to significant changes of phase composition and magnetic properties of amorphous Co80Si9B11 alloy. The activation energy of this process was determined by Kissinger method, which yields Ec=3.0±0.2 eV.Practical implications: According to the results presented in the present paper the examined Co80Si9B11 alloy as a soft ferromagnetic material with high permeability may be utilized in construction of more inductive components and is of great technological interest
Crystallization kinetics of an amorphous Co77Si11.5B11.5 alloy
Purpose: This paper describes crystallization kinetics and changes magnetic properties involved by process of
crystallization Co-Si-B amorphous alloy.
Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD),
electrical resistivity in situ measurements (four-point probe) static and dynamic measurements of magnetic
properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).
Findings: In this work has been performed influence of thermal annealing on crystallization kinetics and
magnetic properties amorphous Co77Si11.5B11.5 alloy.
Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on the
materials as well as for their potential applications, like magnetic sensors. The Co soft magnetic material is used
in noise filters, saturable reactors, miniature inductance elements for abating spike noise, mains transformers,
choke coils, zero-phase current transformers, and magnetic heads etc., i.e., devices which are expected to exhibit high levels of permeability at high frequencies.
Originality/value: It has been shown that thermal annealing at temperature close to the crystallization
temperature leads to a significant increase of the initial magnetic permeability
M\"{o}ssbauer study of the '11' iron-based superconductors parent compound Fe(1+x)Te
57Fe Moessbauer spectroscopy was applied to investigate the superconductor
parent compound Fe(1+x)Te for x=0.06, 0.10, 0.14, 0.18 within the temperature
range 4.2 K - 300 K. A spin density wave (SDW) within the iron atoms occupying
regular tetrahedral sites was observed with the square root of the mean square
amplitude at 4.2 K varying between 9.7 T and 15.7 T with increasing x. Three
additional magnetic spectral components appeared due to the interstitial iron
distributed over available sites between the Fe-Te layers. The excess iron
showed hyperfine fields at approximately 16 T, 21 T and 49 T for three
respective components at 4.2 K. The component with a large field of 49 T
indicated the presence of isolated iron atoms with large localized magnetic
moment in interstitial positions. Magnetic ordering of the interstitial iron
disappeared in accordance with the fallout of the SDW with the increasing
temperature
Incommensurate magnetic order in the alpha-Fe(Te,Se) superconductor systems
Magnetic spin fluctuations is one candidate to produce the bosonic modes that
mediate the superconductivity in the ferrous superconductors. Up until now, all
of the LaOFeAs and BaFe2As2 structure types have simple commensurate magnetic
ground states, as result of nesting Fermi surfaces. This type of
spin-density-wave (SDW) magnetic order is known to be vulnerable to shifts in
the Fermi surface when electronic densities are altered at the superconducting
compositions. Superconductivity has more recently been discovered in
alpha-Fe(Te,Se), whose electronically active antifluorite planes are
isostructural to the FeAs layers found in the previous ferrous superconductors
and share with them the same quasi-two-dimensional electronic structure. Here
we report neutron scattering studies that reveal a unique complex
incommensurate antiferromagnetic order in the parent compound alpha-FeTe. When
the long-range magnetic order is suppressed by the isovalent substitution of Te
with Se, short-range correlations survive in the superconducting phase.Comment: 27 pages, 7 figures, 1 tabl
Investigations of crystallization behaviour of Co80Si9B11 amorphous alloy
Purpose: This paper describes crystallization kinetics and changes of magnetic properties involved by process of crystallization of the amorphous Co80Si9B11 alloy.
Design/methodology/approach: The following experimental techniques were used: X-ray diffraction
(XRD), electrical resistivity in situ measurements (four-point probe), static and dynamic measurements of
magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).
Findings: In this work has been performed influence of thermal annealing on crystallization kinetics and
magnetic properties amorphous Co80Si9B11 alloy.
Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on
the materials as well as for their potential applications, like magnetic sensors. The Co soft magnetic material is
used in noise filters, saturable reactors, miniature inductance elements for abating spike noise, mains transformers, choke coils, zero-phase current transformers, and magnetic heads etc., i.e., devices which are expected to exhibit high levels of permeability at high frequencies.
Originality/value: It has been shown that thermal annealing at temperature close to the crystallization
temperature leads to a significant increase of the initial magnetic permeability. The maximum permeability for
examined alloy in as quenched state is about 11300
Crystallization of amorphous Co77Si11.5B11.5 alloy
Purpose: The investigation results of crystallization of amorphous Co77Si11.5B11.5 alloy in tape form, obtained
by melt spinning method during annealing in temperature range 373-873 K with step of 50 K in time 1 h, have
been presented in the paper.
Design/methodology/approach: The following experimental techniques were used: X-ray diffraction
(XRD), electrical resistivity in situ measurements (four-point probe) static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).
Findings: The changes of magnetic properties connected with the structure changes involved by crystallization
process have been investigated of amorphous Co77Si11.5B11.5 alloy.
Practical implications: Amorphous magnetic materials have been around for some time and their
applications can be found in many types of industrial products. They include transformers, motors, and a wide
variety of magnetic components in sensors, power electronics, electrical energy control/management systems,
telecommunication equipment and pulse power devices.
Originality/value: It has been stated that heat treatment leads to crystallization leads to a significant increase of
the initial magnetic permeability
Incommensurate Magnetism in FeAs Strips: Neutron Scattering from CaFeAs
Magnetism in the orthorhombic metal CaFeAs was examined through
neutron diffraction for powder and single crystalline samples. Incommensurate
() and predominantly
longitudinally () modulated order develops through a 2nd order
phase transition at K with a 3D Heisenberg-like critical
exponent . A 1st order transition at K is
associated with the development of a transverse component, locking to , and increasing the moments from 2.1(1)
to 2.2(3) for Fe and from 1.3(3) to 2.4(4)
for Fe. The {\it ab-initio} Fermi surface is consistent with a nesting
instability in cross-linked FeAs strips.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let
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