Magnetic-crystallographic phase diagram of superconducting parent compound Fe1+x_{1+x}Te

hrough neutron diffraction experiments, including spin-polarized measurements, we find a collinear incommensurate spin-density wave with propagation vector $\mathbf k =$ ($0.4481(4) \, \,0 \, \, \frac1 2$) at base temperature in the superconducting parent compound Fe$_{1+x}$Te. This critical concentration of interstitial iron corresponds to $x \approx 12$ 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 $\mathbf k =$ ($0.3855(2) \, \,0 \, \, \frac1 2$) at base temperature. For a sample with $x \approx 9(1)$, 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 Fe$_{1+x}$Te 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 CaFe4_4As3_3

Magnetism in the orthorhombic metal CaFe$_4$As$_3$ was examined through neutron diffraction for powder and single crystalline samples. Incommensurate (${\bm q}_{\rm m}\approx (0.37-0.39)\times{\bm b}^{\ast}$) and predominantly longitudinally ($\parallel b$) modulated order develops through a 2nd order phase transition at $T_{\rm N}=89.63(6)$ K with a 3D Heisenberg-like critical exponent $\beta=0.365(6)$. A 1st order transition at $T_2=25.6(9)$ K is associated with the development of a transverse component, locking ${\bm q}_{\rm m}$ to $0.375(2){\bm b}^{\ast}$, and increasing the moments from 2.1(1) to 2.2(3) $\mu_{\rm B}$ for Fe$^{2+}$ and from 1.3(3) to 2.4(4) $\mu_{\rm B}$ 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