A comparative study of the magnetoelastic properties of the YFe10V2 and NdFe10V2 compounds

The magnetoelastic properties of iron-rich REFe₁₀V₂ (RE=Nd, Y) compounds were studied via magnetostriction and thermal expansion measurements in the 5–300 K range of temperature in up to 6 T external fields. Results of thermal expansion analysis show that the spontaneous magnetostriction of the compounds mostly originates from itinerant magnetization. Besides, the small volume striction appearing in the thermal expansion of the Nd compound close to 50 K suggests the existence of a basal to conical spin re-orientation transition. The volume magnetostriction isotherms of both compounds take minimum values for external field corresponding to the anisotropy field. In addition, the anisotropic and the volume magnetostriction traces of the NdFe₁₀V₂ take marked maxima under low field, with a relatively large initial magnetostrictivity, again more pronounced at the conical–axial spin re-orientation transition (T_SR=130 K). Analysis of the anisotropic magnetostriction of the Nd compound leads to the conclusion that the contribution of Nd–Fe interactions is negligible. The temperature dependence of volume magnetostriction is in good agreement with prediction of a phenomenological model based upon a fluctuating local band theory. This analysis shows that the difference between the forced volume strictions of Y and Nd compounds below and above T_SR originates from the Nd sublattice magnetization.     

Spin reorientation and magnetization anomaly in Er2Fe14B and Tm2Fe14B

Static magnetic measurements have been carried out on single crystals of Er₂Fe₁₄B and Tm₂Fe₁₄B in a temperature range between 77 and 590 K. Spin reorientation phenomena have been found in both compounds slightly above room temperature. In Er₂Fe₁₄B, the easy direction of magnetization changes from [100] to [001] at 316 K as temperature increases, and Tm₂Fe₁₄B from [100] to [001] at 310 K. Anomalously large anisotropy in the saturation magnetization has been detected around the spin reorientation temperature.     

Enhancement of the magnetostrictive properties of Co0.9Mn0.1Fe2O4 synthesized by using the precursor preparation technique

Co_1−xMn_xFe₂O₄ has been prepared by calcining hydrotalcite-like precursors for the first time. The crystallization behaviors and magnetoelastic properties of the samples have been investigated. The experimental results show that precursor preparation technique is superior compared to the traditional ceramic method. By adopting hydrotalcite-like precursor preparation technique, a fine and more uniform microstructure can be developed. An obvious enhancement of magnetostriction from 95 to 122 ppm and saturation magnetization from 66 to 78 emu/g has been obtained in Co_0.9Mn_0.1Fe₂O₄ composite under lower magnetic filed. This is propitious to apply to sensors and actuators.     

A study on magnetoelastic properties of Tb3 (Fe28−xCox) V1.0 (x=0, 3, 6) compounds

In this work, The magnetoelastic properties of polycrystalline samples of Tb₃ (Fe_28−xCo_x) V_1.0 (x=0, 3, 6) intermetallic compounds are investigated by means of linear thermal expansion and magnetostriction measurements in the temperature range of 77–515 K under applied magnetic fields up to 1.5 T. The linear thermal expansion increases with the Co content. The well-defined anomalies observed in the linear thermal expansion coefficients for Tb₃ (Fe_28−xCo_x) V_1.0 (x=0, 3, 6) compounds are associated with the magnetic ordering temperature for x=0 and spin reorientation temperatures for x=3, 6. Below transition temperatures, the value of the longitudinal magnetostriction (λ_Pa) at 1.6 T increases with Co content.     

High magnetostriction at low fields of (Tb1−xDyx)0.2Pr0.8(Fe0.4Co0.6)1.88C0.05 intermetallic compounds

The structure and magnetostriction of the (Tb_1−xDy_x)_0.2Pr_0.8(Fe_0.4Co_0.6)_1.88C_0.05 intermetallic compounds (0≤x≤1) were studied by X-ray diffraction and magnetic measurements. The formation of an approximate single Laves phase with a MgCu2-type cubic structure was observed in this series of compounds. It was found that the Curie temperature and the saturation magnetization of the compounds would decrease with increase in the Dy content up to x=1. The magnetostriction λ_a (λ_a=λ_‖-λ_⊥) gently rises when x≤0.6, and follows with a precipitous fall when x exceeds 0.6, with the highest value of λ_a being reached in the compounds with x=0.6. The magnetostriction of all the samples was observed to approach their own saturation in the magnetic fields higher than 4 kOe. This indicates that the addition of a small amount of Dy could effectively improve the low-field magnetostriction of the Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.88C_0.05 compounds, which could become a kind of promising magnetostrictive material.     

Critical bond lengths and their role in spontaneous magnetostriction of R2Fe17CX (R=Y,Nd, Gd,Tb, Er)

High-energy high-flux synchrotron X-rays have been used to study the spontaneous magnetostriction of R₂Fe₁₇ (R=Y, Nd, Gd, Tb, Er) and their carbides in the temperature range 10–1100 K. Addition of interstitial carbon greatly increases both the Curie temperatures (T_C) and the spontaneous magnetostrain of the compounds, while reduces the anisotropy of the magnetostrain by expanding the distances between rare-earth and neighboring Fe sites. The increase of T_C with carbon is due to the increased spatial separation of the Fe hexagon layers. On the basal plane, the Fe hexagons are squeezed and the contribution of Fe sublattice to spontaneous magnetostriction is attenuated, while that of rare-earth sublattice is enhanced. The average bond magnetostrain around Fe sites are in linear relation with their hyperfine field intensities.     

Structure and magnetostriction of Tb0.2Pr0.8(Fe0.4Co0.6)1.93−xCx intermetallic compounds

The structure and magnetostriction of Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93−xC_x intermetallic compounds were studied by X-ray diffraction and magnetic measurements. Almost a single cubic Laves phase forms in the alloys for x ≤0.20, and a small amount of C can inhibit the formation of the 1:3 phase. The lattice parameter increases when 0≤x≤0.15, while the T_c and the spontaneous magnetization decreases with increasing x. The lattice parameter decreases slowly when 0.15≤x≤0.30, while the T_c decreases evidently with increasing x. The magnetostriction λ_a (=λ_∥-λ_⊥) is improved at low magnetic fields at room temperature for the compounds with 0.05≤x≤0.10, indicating that these C-containing compounds are promising magnetostrictive materials.     

Magnetic transitions and magnetostrictive properties of Laves compounds Sm0.88Nd0.12(Fe1−xCox)1.93

The structure, magnetic and magnetostrictive properties of Sm_0.88Nd_0.12(Fe_1−xCo_x)_1.93 (0≤x≤1.0) alloys have been investigated. The alloys have the cubic MgCu₂ structure over the whole composition range and the lattice parameter a decreases with increasing x. For 0≤x≤0.2, substitution of Co for Fe slightly increases the saturation magnetization M_s and Curie temperature T_c, while further substitution causes a decrease in both M_s and T_c. The spin reorientation is observed, and a phase diagram for the spin configurations of the Sm_0.88Nd_0.12(Fe_1−xCo_x)_1.93 system is determined. The spontaneous magnetostriction λ₁₁₁ increases as x is increased, while a monotonic decrease of the saturation magnetostriction λ_s with x originates from the increase of λ₁₀₀ with opposite sign to that of λ₁₁₁, which may be caused by the filling of the d band due to Co substitution.     

Relation between anisotropy and crystal structure in rare-earth (3d) transition compounds (R2M17)

The ⁵⁷Fe Mössbauer effect in Fe-rich compounds of the series Tm₂Fe_17?xCo_x was studied, using enriched iron. It was found that there exists a preference for occupancy by the Fe atoms for the f site. This fact proves useful to explain the changes in sign and magnitude of the anisotropy constant observed in other series of rare-earth transition compounds like Y₂Fe_17?xCo_x.     

Temperature dependence of magnetostriction in [Co1−x(FeNi)x]75Si15B10 amorphous alloys

Magnetostriction measurements as a function of temperature and composition are reported for [Co_1x(Fe_0.5Ni_0.5)_x]₇₅Si₁₅B₁₀ metallic glasses. Single-ion as well as two-ion contributions to λ_s are found in the composition range 0<x<0.5. For x=0.12 the magnetostriction changes sign with increasing temperature.     

Influence of the small substitution of Z=Ni, Cu, Cr, V for Fe on the magnetic, magnetocaloric, and magnetoelastic properties of LaFe11.4Si1.6

We have studied the magnetic, magnetocaloric, and magnetostriction properties of LaFe_11.4Si_1.6 and La(Fe_0.99Z_0.01)_11.4Si_1.6 (Z=Ni, Cu, Cr, V) compounds using magnetization and strain gauge techniques. It was found that substitution of 1% of the Fe by Z-elements results in an increase in the Curie temperature (T_C), and affects the magnetostriction and magnetocaloric properties of the parent compound, LaFe_11.4Si_1.6. A maximum shift in T_C of about 11 K, and significantly smaller hysteresis losses in the vicinity of T_C compared with those of the base compound, were found for Z=V. The maximum magnetovolume coupling constant was estimated to be n_dd≈2.7×10⁻³ (μ_B/Fe atom)⁻² for the parent compound. The changes in the volume magnetostriction, the magnetovolume coupling constant, and the magnetocaloric properties are strongly correlated with composition. The relative effects of the variation in cell parameters and electron concentration on the magnetostriction, T_C, and the magnetocaloric properties are discussed.     

Structure,magnetic properties and magnetostriction of laves compounds Nd1−xPrx(Fe0.35Co0.55B0.1)2

The C15 Laves phases with composition Nd_1−xPr_x(Fe_0.35Co_0.55B_0.1)₂ (0?x?1) have been synthesized by arc melting and subsequent annealing. The Curie temperature T_c and the saturation magnetizations M_s at 5 and 295 K decrease with increasing Pr content. The linear anisotropic magnetostriction λ_a=λ_∥−λ_⊥ at room temperature for Nd_1−xPr_x(Fe_0.35Co_0.55B_0.1)₂ alloys with 0?x?0.4 initially reaches a negative minimum, then increases and changes its sign with increasing magnetic field H, and the λ_a for the alloys with x?0.6 is positive and increases as magnetic field H increases.     

Spontaneous volume magnetostriction in Y(Fe1−xCox)2 and Zr(Fe1−xCox)2

The spontaneous volume magnetostriction is calculated for Y(Fe_1?xCo_x)₂ and Zr(Fe_1?xCo_x)₂ in the simple itinerant-electron model. The density of states for various compositions is calculated by the recursion method. The calculated results on the composition dependence of the spontaneous volume magnetostriction are shown to be consistent with the experimental ones.     

Effect of Nb and Cr incorporation on the structural and magnetic properties of rapidly quenched FeCoSiB microwires

Rapidly quenched microwires with a nominal composition of Fe₃₉Co₃₉Si₈B₁₄ (#A_O), Fe₃₇Co₃₇Nb₄Si₈B₁₄ (#A_N) and Fe₃₆Co₃₆Nb₄Cr₂Si₈B₁₄ (#A_NC) have been investigated. Devitrification of as-quenched microwires showed that crystallization temperatures increased with simultaneous incorporation of Nb and Cr as in #A_NC alloy. Addition of these elements also contributed to an increase in activation energy in #A_N and #A_NC alloys. Nb addition reduced the particle size, which became much finer in the case of the Cr-containing alloy. Although Nb addition did not have much effect on lowering the Curie temperature T_C of the amorphous phase, Cr substitution lowered T_C to 698 K from high values of 785 K and 787 K observed in the #A_O and #A_NC alloys, respectively. However, the Cr addition revealed a better Giant magneto-impedance (GMI) response compared to the other alloys. Such improved GMI properties in the Cr-containing alloy are attributed to lower values of the coercivity and magnetostriction in the alloy containing both Nb and Cr.     

Effect of hydrogenation on the magnetic and magnetoelastic properties of R 2Fe14B compounds (R = Nd, Gd, Er, Lu)

The temperature dependences of the magnetization σ(T), magnetostriction λ(T), and linear thermal expansion coefficient α(T) of R ₂Fe₁₄B intermetallic compounds (R = Nd, Gd, Er, Lu) and of their hydrides R ₂Fe₁₄BH_2.5 are studied. The magnetization was measured with a pendulum magnetometer within the temperature interval 77–700 K in a magnetic field H = 500 Oe. Magnetostriction and thermal expansion were measured using the tensometric technique in the temperature interval 77–420 K. It was established that Gd₂Fe₁₄BH_2.5 undergoes a spin-reorientational (SR) transition at T _SR = 235 K. In compounds with Nd and Er, anomalies associated with the SR transition were found in the σ(T), λ(T), and α(T) curves. The SR transition temperatures were refined and magnetic phase diagrams were constructed for the compounds studied. The α(T) curves of the R ₂Fe₁₄BH_2.5 hydrides (R = Nd, Er) revealed anomalies of a nonmagnetic origin associated with hydrogen ordering in the crystal lattice of these compounds.     

Effect of Nb addition on the structure and soft magnetic properties of melt-spun Co69Fe7Si14B10 alloy

Melt-spun ribbons of Co₆₉Fe₇Si_14−xNb_xB₁₀ alloys with x=0, 2 and 4 have been prepared and characterized for structure and soft magnetic properties. Ribbons with x=0 and x=2 are found to be completely amorphous whereas the ribbon with x=4 contains irregular shaped faulted Co₂Si orthorhombic phase with grain size of about 100 nm. Nb addition is found to decrease the degree of amorphicity and induce perpendicular anisotropy, deteriorating the soft magnetic and magnetoimpedance properties.     

Effect of hydrogenation on the magnetic and magnetoelastic properties of the Tb0.27Dy0.73Fe2 and Tb0.27Dy0.73Co2 compounds with compensated magnetic anisotropy

The effect of hydrogenation on the magnetic ordering temperature and magnetostriction of the Tb_0.27Dy_0.73Fe₂ and Tb_0.27Dy_0.73Co₂ compounds with compensated magnetic anisotropy of the rare-earth sublattice was studied. It was established that the incorporation of hydrogen atoms into the crystal lattice of the compounds studied lowers the Curie temperature. It is shown that, in this case (i.e., for structures of the Laves phase type), the decrease in T _C results primarily from the change in the electronic structure of these compounds. An anomaly was found in the temperature dependence of thermal expansion of Tb_0.27Dy_0.73Co₂ and its hydride. It was established that hydrogenation brings about a substantial weakening of magnetostriction, which should be attributed to a change in the local electronic density induced by the incorporation of hydrogen atoms into the crystal lattice. __________ Translated from Fizika Tverdogo Tela, Vol. 47, No. 10, 2005, pp. 1834–1838. Original Russian Text Copyright ? 2005 by Politova, Tereshina, Nikitin, Sochenkova, Verbetsky, Salamova, Makarova.     

Magnetic resonance study of phases in FeVO4-Co3V2O8 system

Multicomponent vanadates Co_3+xFe_4−xV₆O₂₄ have been synthesized using the solid state reaction method from Co₃V₂O₈ and FeVO₄.oxides. The electron paramagnetic resonance/ferromagnetic resonance (EPR/FMR) spectra of 20 samples containing solid state phases formed in the FeVO₄-Co₃V₂O₈ system have been recorded at room temperature. The howardevansite structure (H-type phase) is produced, which corresponds to the Co_2.616Fe_4.256V₆O₂₄ formula while a homogeneity range of lyonsite (L-type phase) type structure could be described by the Co_3+1.5xFe_4−xV₆O₂₄ formula (0.476<x<1.667). Considering the values of g-factor and linewidth of each registered spectrum the existence of three types of magnetic centers was inferred and correlated with phases detected by XRD method.     

Electrical resistivity and magnetic susceptibility studies of the system Mn5Si3-Fe5Si3

Electrical resistivity measurements have been performed on the system Mn_5?x,Fe_xSi₃ for the compounds x = 0,1,2,3,4 and 5 from 4.2 K to above room temperature. From the shape of the ρ(T) curves it can be inferred that the transition from antiferromagnetic to ferromagnetic ordering occurs in the concentration range 3 ? x ? 4; for Fe₅Si₃ and MnFe₄Si₃ the ρ(T) curves are characterized by a break in their slope, whereas for x = 1,2 and 3 a large minimum appears. Mn₅Si₃ exhibits two successive minima at 74 and 105 K. Magnetic susceptibility measurements for x = 1, 2 and 3 give confirmation of the Néel temperature for x = 1 and 2, whereas for x = 3 the behaviour is more complex.     

A survey on the effect of vanadium content on the magnetoelastic properties of YFe12−xVx alloys

Experimental results on the thermal expansion and magnetostriction of YFe_12−xV_x (1.5≤x≤3.5) alloys are reported. The results show that the anisotropic magnetostriction (Δλ) at a finite field (1.5 T) increases with increasing vanadium content in the range of x<2. But for x>2, a decrease in the magnetic anisotropy with increasing vanadium content causes a decrease in the saturation values of Δλ. In addition, the thermal expansion coefficient becomes a minimum for x≈2. Experimental curves exhibit that the forced volume magnetostriction (ΔV/V) is positive and increases linearly with the applied field at high fields. But in the low field region (≤0.5 T), a minimum appears in the isothermal curves of ΔV/V around the saturation field. The results are explained by considering the influence of vanadium content on the magnetization anisotropy of YFe_12−xV_x compounds.