Effect of tensile stresses on the Δ<Emphasis Type="Italic">E</Emphasis> effect in ferromagnetic Fe<Subscript>64</Subscript>Co<Subscript>21</Subscript>B<Subscript>15</Subscript> ribbons

Effect of elastic tensile stresses on the Δ E -effect magnitude in ferromagnetic Fe₆₄Co₂₁B₁₅ amorphous ribbons subjected to magnetic annealing and dc treatment was studied. In the case of relatively low tensile stresses, the maximum magnitude of the negative Δ E effect in the ribbons under study is shown to increase whatever their treatment. The subsequent increase in elastic tensile stresses leads to a decrease in the maximum value of the negative ΔE effect. The maximum sensitivity of the ΔE effect to the applied elastic tensile stresses is characteristic of samples subjected to magnetic annealing. The results obtained are explained using a conception of the effect of magnetic domain structure and mechanisms of its transformation induced by magnetic field and elastic tensile stresses on the ΔE effect in amorphous ferromagnetic ribbons.     

On the temperature behavior of a tensoresistive effect in the amorphous Fe<Subscript>80</Subscript>B<Subscript>14</Subscript> alloy

Investigation of the temperature behavior of the coefficient of tensoresistance π of the amorphous Fe₈₆B₁₄ alloy in a temperature range from room temperature to the crystallization temperature has been carried out. It has been revealed that below the Curie temperature T _C, in the interval of existence of elinvar properties, π in this alloy increases only weakly, with a temperature coefficient of 4 × 10^?4 K^?1. At T > T _C, a stronger temperature increase of π is observed. An analysis performed has shown that the most probable reason of the observed temperature changes in π was a temperature-induced change in Young’s modulus of the alloy. It has been shown that during crystallization the coefficient of tensoresistance π decreases with increasing amount of crystalline phases in the alloy.     

Inverse magnetocaloric effect in the uniaxial paramagnet with non-Kramers ions

It has been shown that, in a uniaxial paramagnet with non-Kramers ions with a spin of S = 1 and single-ion anisotropy of the easy-plane type (DS _Z ² ), there is a low-field (μ₀ H ≤ D) and low-temperature (k _B T < 0.68D) region in which the isothermal magnetization along the hard direction H||OZ increases the magnetic entropy by ΔS _M (T, ΔH = H _f - H _i > 0) > 0 and the adiabatic magnetization along the same direction reduces the sample temperature by ΔT _ad(T, ΔH > 0) < 0 (inverse magnetocaloric effect (MCE)). The main features of the inverse MCE in uniaxial paramagnets with large spins (S = 2, 3, …) of the non-Kramers ions have been discussed.     

Properties of the Ti<Subscript>40</Subscript>Zr<Subscript>10</Subscript>Cu<Subscript>36</Subscript>Pd<Subscript>14</Subscript> BMG Modified by Sn and Nb Additions

The results of investigation of the influence of additions of 2 and 3 at.% of Sn and simultaneously of Sn and 3 at.% Nb on microstructure and properties of the bulk metallic glasses of composition (Ti₄₀Cu_36?x Zr₁₀Pd₁₄Sn _x )_100?y Nb _y are reported. It was found that the additions of Sn increased the temperatures of glass transition (T _g), primary crystallization (T _x ), melting, and liquidus as well as supercooled liquid range (ΔT) and glass forming ability (GFA). The nanohardness and elastic modulus decreased in alloys with 2 and 3 at.% Sn additions, revealing similar values. The 3 at.% Nb addition to the Sn-containing amorphous phase decreased as well all the T _g, T _x , T _L, and T _m temperatures as ΔT and GFA; however, relatively larger values of this parameters in alloys containing larger Sn content were preserved. In difference to the previously published results, in the case of the amorphous alloys containing small Nb and Sn additions, a noticeable amount of the quenched-in crystalline phases was not confirmed, at least of the micrometric sizes. In the case of the alloys containing Sn or both Sn and Nb, two slightly different amorphous phase compositions were detected, suggesting separation in the liquid phase. Phase composition of the alloys determined after amorphous phase crystallization was similar for all compositions. The phases Cu₈Zr_3, CuTiZr, and Pd₃Zr were mainly identified in the proportions dependent on the alloy compositions.     

Study of Ferrous Ternary Diagrams in Relation to Magnetic Interactions: Fe-Ni-AI System

A thermodynamic analysis of the y loop in iron alloys recently published by Zener¹ was applied to the ternary phase diagram Fe-Ni-AI. From this analysis two separate parameters, ΔT_martensite and ΔT_martensite were obtained, which describe the influence of the alloying elements upon the magnetic transformation range and a hypothetical martensite temperature, respectively. Extrapolation of the resulting values, plotted against the atomic fraction Ni/(Ni+AI), indicates an anomalous effect of aluminum on the ferromagnetic characteristics of iron. An interpretation of the anomaly is advanced in terms of short range magnetic order above the Curie point.     

The effect of alloying molybdenum additives on the hyperfine structure and corrosion-electrochemical behavior of Fe-Cr alloys

With the use of Mössbauer spectroscopy, the effect of alloying molybdenum additives on the hyperfine magnetic and electronic structure of iron alloys containing ～21 and 28% chromium is studied. Probability distribution functions of hyperfine magnetic fields P(H _eff), intensities of the effective magnetic field H _eff, isomer (chemical) shifts δ, second-to-third spectral line area ratios (W ₂₃), and other spectral parameters are calculated with the use of the Normos program package. The data of Mössbauer spectroscopy are compared to the corrosion-electrochemical behavior of the alloys.     

Origin and specific features of invar anomalies of physical properties: Fe-Ni alloys with an FCC lattice

In their physical properties, the γ-Fe-Ni alloys can be separated into three groups of materials: invars, high-nickel alloys, and medium-nickel alloys of the transition class. In the invars and alloys of the transition class in the temperature interval ΔT adjoining T _C, a weak ferromagnetic state arises. In high-nickel alloys and transition alloys at temperatures below t _f, a strong ferromagnetic state exists. The invar anomalies of physical properties in γ-Fe-Ni alloys are observed in the temperature range in which there occurs a transition from the weak ferromagnetic into strong ferromagnetic state.     

Investigation of the magnetocaloric effect in correlated metallic systems with Van Hove singularities in the electron spectrum

In this work, the magnetic contribution to the isothermal entropy change ΔS upon switching on a magnetic field has been investigated in correlated metallic ferromagnets within the Hubbard nondegenerate model. The analytical expression ΔS for obtained in the mean-field approximation depends substantially on the electronic structure (density of electron states), which presents new ways to increase the absolute value of ΔS relative to the known result obtained within the Heisenberg model. The temperature dependence of ΔS has been calculated at different values of the Coulomb interaction U and the number of electrons n for the Bethe infinite-dimensional lattice and square lattice with allowance for transfer integrals in the first (t) and the second (t') coordination shells. It has been found that the presence of Van Hove singularities in the electronic spectrum near the Fermi level makes it possible to considerably increase |ΔS| at a fixed magnetic field. The possibility of first-order magnetic phase transitions depending on the model parameters has been analyzed.     

Magnetic and structural properties of rapidly quenched Nd-Fe-Co-Ge-B alloys

We have studied the magneto-resistive effect in bulk Y_3/4Lu_1/4Ba₂Cu₃O₇ + CuO composites prepared by the fast-sintering technique. It has been found that the composites exhibit large magnetoresistance in low magnetic fields (<100 Oe) in a broad temperature range (tens of kelvins below the critical temperature T _c). The HTSC-based composites exhibit a much higher sensitivity to weak magnetic fields at liquid-nitrogen temperature as compared to pure HTSC ceramics. By choosing a proper bias current j, it is possible to control the shape of the resistivity-magnetic field ρ(H) characteristic of the composites and to vary the parameter R ₀ = {R(H = 0) ? R(H)}/R(H = 0). Under the condition j > j _c (where j _c is the critical-current density), large values of the magnetoresistance R ₀, up to thousands percent, are obtained in the range of weak magnetic fields (tens of oersteds) at 77 K. This effect is attractive for practical applications of these composite materials as active elements of magnetic-field sensors. The sign of the magneto-resistive effect is positive in contrast to that of manganese oxides. This may be important for some devices.     

Characteristics of thermoelastic martensitic transformation in ferromagnetic Fe-Co-Ni-Ti alloys alloyed with Cu

The effect of alloying of Fe-Ni-Co-Ti compositions with copper on their structure and some magnetic characteristics is studied. The investigations performed showed that the alloys under study exhibit a tendency to cellular decomposition at T ≥ 550°C; at T ≤ 500°C, the continuous precipitation of an intermetallic phase is mainly observed. The temperature and field dependences of the magnetization of martensite in the Fe-Ni-Co-Ti alloys have been measured; the width of the temperature hysteresis of the martensitic transformation in aged alloys has been determined.     

Changes in the temperatures of phase transformations of the Ni<Subscript>2</Subscript>MnGa alloy upon substitution of nickel for manganese

Temperatures of phase transformations of a number of Ni₂MnGa-based alloys (four compositions), which are characterized by substitution of nickel for manganese at an unchanged gallium content (25 at %), have been determined. As the nickel concentration increases with respect to the stoichiometric composition (or the electron concentration e/a increases), the liquidus (T _liq), solidus (T _sol), and martensitic transformation (T _mart) temperatures increase, whereas the magnetic transformation temperature (T _C) decreases slightly.     

Creep correlations of metals at elevated temperatures

Creep data for pure metals at temperatures above those at which rapid recovery occurs (above about 0.45 the melting temperature) are correctable by means of the equations ? = f (te^?ΔH/RT, σ) and σ = f (?&#x0307 _s e^ΔH/RT). These correlations were applied successfully to data for aluminum, iron, nickel, copper, zinc, platinum, gold, and lead as well as for simple alloys. For a given metal, ΔH is a constant about equal to the activation energy for self-diffusion.     

1:13 phase formation mechanism and first-order magnetic transition strengthening characteristics in (La,Ce)Fe<Subscript>13–<Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

The effects of the introduction of Ce to La_1?x Ce _x Fe_11.5Si_1.5 alloys on 1:13 phase formation mechanism, the first-order magnetic phase transition strengthening characteristics, and magnetocaloric property were studied, respectively. The results show that the formation mechanisms of 1:13 and LaFeSi phases in La_1?x Ce _x Fe_11.5Si_1.5 alloys are the same as those of Ce₂Fe₁₇ and CeFe₂ phases in Ce–Fe binary system, respectively. The substitution of Ce in 1:13 phase which is limited can make the first-order magnetic phase transition characteristics strengthen, which can make thermal and magnetic hysteresis increase, the temperature interval of temperature-induced phase transition decrease, and the critical magnetic field of field-induced magnetic phase transition (H _C) increase, respectively. Owing to the lattice shrink of 1:13 phase with the increase in Ce content, the Curie temperatures (T _C) show a linear decrease. The maximum change in magnetic entropy gradually increases due to the decrease in temperature interval of temperature-induced phase transition, but the relative cooling capacities are all about 80 J·kg^?1 at magnetic field of 2 T.     

Optimum Combination of Thermoplastic Formability and Electrical Conductivity in Al–Ni–Y Metallic Glass

Both thermoplastic formability and electrical conductivity of Al–Ni–Y metallic glass with 12 different compositions have been investigated in the present study with an aim to apply as a functional material, i.e. as a binder of Ag powders in Ag paste for silicon solar cell. The thermoplastic formability is basically influenced by thermal stability and fragility of supercooled liquid which can be reflected by the temperature range for the supercooled liquid region (ΔT_x) and the difference in specific heat between the frozen glass state and the supercooled liquid state (ΔC_p). The measured ΔT_x and ΔC_p values show a strong composition dependence. However, the composition showing the highest ΔT_x and ΔC_p does not correspond to the composition with the highest amount of Ni and Y. It is considered that higher ΔT_x and ΔC_p may be related to enhancement of icosahedral SRO near T_g during cooling. On the other hand, electrical resistivity varies with the change of Al contents as well as with the change of the volume fraction of each phase after crystallization. The composition range with the optimum combination of thermoplastic formability and electrical conductivity in Al–Ni–Y system located inside the composition triangle whose vertices compositions are Al₈₇Ni₃Y₁₀, Al₈₅Ni₅Y₁₀, and Al₈₆Ni₅Y₉.     

Magnetostructural investigation of ball-milled cobalt-copper alloy

In this work we investigate a metastable inhomogeneous Co-Cu alloy produced by mechanical alloying. We use both conventional structural method (X-ray diffraction) and magnetic measurements of M(T) and M(H) dependences to obtain additional information about the process of mechanical alloying.     

Low-temperature properties of the orderable Cu<Subscript>3</Subscript>Pd alloy

The effect of atomic ordering on the transport properties of the Cu₃Pd alloy in the low-temperature range (T < 70K) in strong magnetic fields (H ≤ 150 kOe) has been studied. The temperature dependence of the resistivity during alloy disordering has been found to have a minimum at T ～ 10 K. The Hall effect has a negative sign. The magnetoresistance, on the contrary, is positive; the longitudinal effect equals ～50% of the transverse one.     

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT_⊥) on the permeability of the amorphous alloy Co₆₉Fe_3.7Cr_3.8Si_12.5B₁₁ with such a low saturation magnetostriction (λ_s 10^–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (K_sq > 0.90). It has been revealed that the permeability μ₄ (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop K_sq,m in the range of 0.2 ≤ K_sq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ₄ (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe₅₇Co₃₁Si_2.9B_9.1 with λ_s = 35 × 10^–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT_⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.     

On the problem of chromium effect on the passivability of Fe-Cr alloys

The hyperfine magnetic and electronic structure of annealed iron alloys containing 9.0, 11.8, and 12.7% chromium is studied using of Mössbauer spectroscopy. Probability distribution functions of hyperfine magnetic fields P(H_eff), mean-square intensities of the effective magnetic field H _{eff, m-sq}, average isomer (chemical) shifts δ, and other spectral parameters are calculated with the use of computer modeling. Data from Mössbauer spectroscopy are compared to the results of polarization measurements in 1 N H₂SO₄ solution at room temperature in order to find the correlation between the electronic structure and the passivability of the alloys studied.     

Microstructure and magnetic properties of <Emphasis Type="Italic">R</Emphasis>-Fe-B-Cu (<Emphasis Type="Italic">R</Emphasis> = Pr,Nd) alloys deformed by equal-channel angular pressing and subsequent hot upsetting

Effects of equal-channel angular pressing with controlled back pressure (ECAP-BP) and subsequent upsetting on the formation of the texture, magnetic properties, and changes in the microstructure of R-Fe-B-Cu (17–20 at. % R, R = Pr, Nd) alloys have been investigated. It has been shown that, under the action of ECAP-BP at 470°C, a high coercive force H _c arises and a diametral texture is formed in the Pr-Fe-B-Cu alloys. Application of hot compression to alloys processed by ECAP-BP increases the degree of texture if the compression is applied in the direction of the initial texture axis or reorientes the texture axis in the direction of compression if the compression is applied in the direction perpendicular to the initial texture. It has been established that to obtain a high level of magnetic hysteresis properties in the Nd-Fe-B-Cu alloys, the combined hot deformation of these alloys should be carried out at temperatures above 500°C.     

Structure,magnetic and magnetocaloric properties of nonstoichiometric TbCo<Subscript>2</Subscript>Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> compounds

The structure and magnetic and magnetocaloric properties of new nonstoichiometric TbCo₂Ni _x compounds (0 ≤ x ≤ 0.4) have been studied. The alloys with х ≤ 0.1 have been shown to be single-phase with the MgCu₂-type structure; in alloys with х > 0.1, an additional phase with a PuNi₃-type structure has been formed. It has been found that the concentration dependences of the Curie temperature and magnetic moment of the 3d-metal sublattice have a maximum at x = 0.025. The magnetocaloric effect magnitude for the TbCo2Nix compounds has been estimated using the results of magnetic and heat-capacity measurements.