Co50Ni22Ga28:Fex单晶在室温和100℃高温的超弹性研究

制备了四元铁磁性Heusler合金Co₅₀Ni₂₂Ga_{28：Fex（x＝0，1.5，2，2.5），发现材料具有很好的机械性能，在加压、 弯曲和扭曲时都展现出很好的超弹性.室温时，在压力作用下，Co50Ni22< /sub>Ga28：Fe2单晶样品在［001］和［110］方向分别具有约4%和 6.7%的完全可恢复应变.Co50Ni22Ga28：Fe1.5单晶样品在室温下沿［001］和［110］方向的应力与应变σ-ε曲线的平台部分较缓， 但升温到100℃时，σ-ε曲线中表示超弹性应变的平台变平.Co50Ni22Ga28 ：Fe2.5成分的单晶在［001］方向可得到5.5%的超弹性应 变.同时以上材料都显示出了明显的弹性各向异性. 关键词： 铁磁性Heusler合金 超弹性 50Ni22Ga28：Fex')" href="#">Co50Ni22Ga28：Fex}     

Magnetism in FeAl,CoAl, CoGa and NiAl

Isothermal magnetization vs field data from 1.6 to 300°K for Ni_0.48Al_0.52, Ni_0.50Al_0.50, Co_0.48Al_0.52 and Co_0.50Al_0.50 can be described in terms of contributions from magnetic clusters, from “antistructure” transition metal atoms on Al sites, and from a field- and temperature-independent susceptibility. The moment of antistructure Ni is 0.3μ_B in both nickel alloys. In both cobalt aluminides as well as in Co_0.47Ga_0.53, the antistructure Co moment is 1μ_B. The moment of antistructure Fe in Fe_0.49Al_0.51 is 2.2μ_B.     

Effect of quenching wheel speed on the structure, magnetic properties and magnetoimpedance effect in Co64Fe4Ni2B19−xSi8Cr3Alx (x=0, 1 and 2) melt-spun ribbons

Melt-spun ribbons of Co₆₄Fe₄Ni₂B_19−xSi₈Cr₃Al_x (x=0, 1 and 2) alloy at wheel speed of 25 m/s and Co₆₄Fe₄Ni₂B_19−xSi₈Cr₃Al₁ alloy at different wheel speeds (25, 30, 35 and 40 m/s) have been prepared and investigated for structural and magnetic properties and magnetoimpedance effect. Based on the results obtained, it was shown that replacement of B by Al can improve the magnetoimpedance ratio (MIR) and the highest value of MIR (191%) was observed for the sample with X_Al=1 at wheel speed of 25 m/s. Further, it was seen that the higher quenching wheel speed gives rise to a higher coercivity and lower magnetic permeability/MIR value.     

掺Mn对NiFeGa磁性形状记忆材料单晶特性的影响

在单晶Ni₅₄Fe₁₉Ga₂₇中掺入少量Mn，对增强磁交换相互作用，提高居里温度和稳定了B2相并增强晶格的刚度，起到了非常明显的作用.Mn的存在使样品中取向内应力得以保持，提高了变体择优取向的水平，大大提高了单晶的相变应变和磁场增强作用.发现内应力对超弹性性质的影响也很明显. 关键词： 磁性形状记忆合金 NiFeGa 单晶 超弹性     

Segregation of Solutes in Two-Phase Mixtures

Fractions of indium solutes in each phase of a mixture of two binary phases were measured using perturbed angular correlation of gamma rays. Measurements of phase fractions were made on Pd₃Ga₇–PdGa, PdGa–Pd₅Ga₃, and FeAl₂–FeAl mixtures as a function of composition. The phase fractions were analyzed using a thermodynamic model that takes into account differences between energies of solute atoms in the two phases. From the model, segregation coefficients were obtained for the systems studied. Also, earlier measurements on Ni₂Al₃–NiAl were reanalyzed. Large differences are found among the segregation coefficients. This revised version was published online in September 2006 with corrections to the Cover Date.     

A New Highly Sensitive and Selective Fluorescent Cadmium Sensor

Condensation product (L) of salicylaldehyde and semicarbazide behaves as a fluorescent sensor for Cd²⁺ ion, in 1:1 DMSO:H₂O, over Mn²⁺, Fe²⁺, Ni²⁺, Co²⁺, Cu²⁺, Pb²⁺ and Hg²⁺ ions. The emission peak of L at λ_max = 520 nm, on excitation with 420 nm wavelength photons, showed an enhancement in intensity of ca 60-fold when interacted with Cd²⁺ ion. The intensity was however found to remain unaltered when interacted with metal ions—Mn²⁺, Fe²⁺, Ni²⁺, Co²⁺, Cu²⁺, Pb²⁺ and Hg²⁺. The intensity increases by approximately 20 fold on interaction with Zn²⁺ ion. The increase in the fluorescent peak can be explained on the basis of photo induced electron transfer (PET) mechanism. A 1:1 complexation between Cd²⁺ and L with log β = 4.25 has been proved.     

Multilevel interaction between layers in layered film structures

An analysis was carried out of the mechanism underlying magnetic interlayer interaction in film structures. The investigation was based on the assumption that interlayer bonding affects film hysteresis. This was based on experimental data on the coercive force, the domain structure parameters, and the microstructure of Fe₁₉Ni₈₁/Cr/Fe₁₉Ni₈₁ and Fe₁₅Co₂₀Ni₆₅/Cr/Fe₁₅Co₂₀Ni₆₅ films. Theoretical estimates show that, as the thickness of the Cr interlayer increases, the exchange interaction between the ferromagnetic layers can be replaced by the magnetostatic interaction whose effectiveness is determined by surface irregularities and layer ‘magnetization ripples’. Fiz. Tverd. Tela (St. Petersburg) 39, 2191–2194 (December 1997)     

Thickness-dependent magnetic properties of Ni81Fe19, Co90Fe10 and Ni65Fe15Co20 thin films

We present results of magnetization and magnetic anisotropy measurements in thin magnetic films of the alloys Ni₈₁Fe₁₉, Co₉₀Fe₁₀ and Ni₆₅Fe₁₅Co₂₀ that are commonly used in magnetoelectronic devices. The films were sandwiched between layers of Ta. At room temperature the critical thickness for all the films to become ferromagnetic is in the range 11–13 Å. In Co₉₀Fe₁₀ the coercivity and the anisotropy field both depend strongly on layer thickness.     

Spectral and scintillation characteristics of compound x-ray detectors based on calcium iodide crystals

The results of an investigation of the spectral and scintillation properties of pure and Tl⁺, Eu²⁺, Fe²⁺, Co²⁺, and Ni²⁺ activated calcium iodide crystals as well as the results of measurements of the scintillation characteristics of compound x-ray detectors based on calcium iodide crystals are reported. It is shown that paired CaI₂ and CaI₂:Tl crystals can be used to fabricate compound detectors with different fluorescence times. On account of their high light output and good energy resolution CaI₂ and CaI₂:Eu crystals are suitable for compound detectors with different technical light output. CaI₂ or CaI₂:Eu scintillators together with scintillators based on calcium iodide with iron-group luminescence quenching impurity (Fe²⁺, Co²⁺, and Ni²⁺) can be used to obtain compound detectors with different physical light output. Zh. Tekh. Fiz. 68, 71–73 (September 1998)     

Spin-dependent current and magnetization reversal in Tb22Co5Fe73/Pr6O11/Tb19Co5Fe76 nanofilms in laser radiation field

The results of investigation of magnetization reversal dynamics of ferrimagnetic amorphous nanolayers with transverse anisotropy is investigated for Al₂O₃/Tb₂₂Co₅Fe₇₃/Al₂O₃ and Al₂O₃/Tb₂₂Co₅Fe₇₃/Pr₆O₁₁/Tb₁₉Co₅Fe₇₆/Al₂O₃ multilayer films irradiated by laser pulses, as well as the effect of such irradiation on the resistance in a Tb₂₂Co₅Fe₇₃/Pr₆O₁₁/Tb₁₉Co₅Fe₇₆ tunnel microcontact. It is shown that magnetization reversal in magnetic nanolayers in the laser radiation field may occur not only because of heating and the action of the external magnetic field, but also under the action of the magnetic field induced by circularly polarized laser radiation, as well as owing to transfer of magnetic moments by polarized electrons. Laser radiation can be used to control (by changing the resistance by a factor of 1.5–2.0) the conductivity of the Tb₂₂Co₅Fe₇₃/Pr₆O₁₁/Tb₁₉Co₅Fe₇₆ tunnel microresistor. Original Russian Text ? N.N. Krupa, 2009, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2009, Vol. 108, No. 5, pp. 981–992.     

Hyperfine interactions, structure and magnetic properties of nanocrystalline Co–Fe–Ni alloys prepared by mechanical alloying

Mechanical alloying method was used to prepare nanocrystalline Co₅₀Fe₄₀Ni₁₀, Co₅₂Fe₂₆Ni₂₂ and Co₆₅Fe₂₃Ni₁₂ alloys. X-ray diffraction proved that during milling Co–Fe-based solid solution with b.c.c. lattice was formed in the case of Co₅₀Fe₄₀Ni₁₀, while for Co₅₂Fe₂₆Ni₂₂ and Co₆₅Fe₂₃Ni₁₂ compositions Co–Ni-based solid solutions with f.c.c. lattice were obtained. Mössbauer spectroscopy revealed similar values of the average hyperfine magnetic fields for all alloys, e.g. 32.17, 32.24 and 31.21 T for Co₅₀Fe₄₀Ni₁₀, Co₅₂Fe₂₆Ni₂₂ and Co₆₅Fe₂₃Ni₁₂ alloys, respectively. Magnetization measurements allowed to determine the effective magnetic moment, Curie temperature, saturation magnetization and coercive field for the obtained alloys.     

Modification of the optical spectra of mixed K2CoxNi1–x(SO4)2?6H2O crystals

We propose a new method for obtaining K₂Co _x Ni_1–x (SO₄)₂⋅6H₂O (x = 0, 0.4, 0.8, 1) crystals, involving the use of the chlorides (CoCl₂⋅6H₂O and NiCl₂⋅6H₂O) in an aqueous solution instead of the widely used sulfates. We have studied the transmission spectra of the grown single crystals in the range λ = 200–900 nm and the IR reflectance spectra in the 2.5–20 μm region. We have observed a change in the position and intensity of the absorption bands as a function of the composition of the crystals. Based on the Tanabe–Sugano diagrams, we determined the crystal field splitting (D_q) and its dependence on the nickel concentration. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 126–130, January–February, 2009.     

Synthesis of industrial diamonds using FeNi alloy powder as catalyst

Synthesis of diamond single crystals in Fe80Ni20 C system was carried out in a cubic anvil high-pressure and high-temperature apparatus. This paper reports that the surface morphology and inclusion distribution of the grown diamonds had been observed. It finds that the inclusions in cubic and octahedral diamonds radiated along certain crystal orientation, while the inclusion distribution in cubo-octahedral diamond seemed independent of crystal orientation. By using scanning electron microscope, the surface morphology of the three shapes of diamonds was observed. The results of Mossbauer spectrum indicated that there were iron-inclusions FeaC and Fe-Ni alloy in the diamonds. According to the Fe-C phase diagram, FeaC should have formed during the quenching process. Nickel might have an inhibitory effect on the formation of Fe3C.     

Stress–strain–temperature behaviour of [001] single crystals of Co49Ni21Ga30 ferromagnetic shape memory alloy under compression

The conventional shape memory effect (SME) and pseudoelasticity (PE) in as-grown [100] single crystals of Co₄₉Ni₂₁Ga₃₀ alloy under compression are reported. The parent single crystals exhibit about 5% transformation strain at compressive stress levels as low as 4?MPa, and a pseudoelastic strain of 4.5%. Complete PE was observed in the temperature range from 35 to 285°C, along with increasing stress hysteresis with temperature. The latter is attributed to increasing number of variants and the corresponding variant–variant interactions. We demonstrate that the current material can be utilized in applications that demand high strength at elevated temperatures. Moreover, the current results also indicate the potential of this material to exhibit magnetic shape memory effect, which could broaden the scope of utility of this material upon further research.     

Kondo effect due to substitutional atoms in NiAl

The electrical resistivity and the magnetization have been measured in the CsCl-type compounds, Ni_xAl_1?x, (Ni_0.75Co_0.25)_0.52Al_0.48 and Ni_0.90Fe_0.10)_0.52Al_0.48. A Kondo effect is observed due to substitutional Co and Fe atoms.     

Anomalous behavior of curves of pseudo-elastic deformation of Ni–Fe–Ga–Co alloy crystals as a result of interphase stresses

The compression diagram of Ni₄₉Fe₁₈Ga₂₇Co₆ alloy crystals in the [011] direction was studied until full shape memory strain at various temperatures in the range of 259–340 K. It is found that all load curves are anomalously shaped and contain portions of sharp and gradual decreases in deformation stresses. Simulation of pseudo-elastic stress–strain curves within the theory of diffuse martensitic transitions, describing not only equilibrium of phases, but also the kinetics of the transition between them, shows that elastic interphase stresses during martensitic reactions Ll ₂ → 14M and 14M → Ll ₀ characteristic of this alloy can be responsible for the extraordinary shape of compression diagrams.     

Magnetostriction of Fe81Ga19 oriented crystals

The effect of the orientation on the magnetostriction in Fe 81 Ga 19 alloy has been investigated experimentally and theoretically.The Fe 81 Ga 19 [001] and [110] oriented crystals were prepared and the magnetostriction was measured under different pre-stress.The saturation magnetostriction of the [001] oriented crystal increases from 170×10-6 to 330×10-6 under the pre-stress from 0 to 50 MPa.The [110] oriented crystal has a saturation magnetostriction from 20×10-6 to 140×10-6 with the compressive pre-stress from 0 to 40 MPa.The magnetostriction of [001] and [110] oriented crystals has been simulated based on the phenomenological theory.The domain rotation path has been determined and the resultant magnetostriction calculated under different pre-stress.The experimental and simulated results both show that the [001] oriented crystal exhibits better magnetostriction than [110] oriented crystal.The enhancement of the saturation magnetostriction by the compressive pre-stress in the [110] oriented crystal is higher than that in the [001] oriented crystal.     

57Fe/Co Multilayers Investigated by CEMS and Nuclear Resonance Reflectivity Time Spectra Using Grazing Incident SR

[Fe₆Co₃] and [Fe₅Co₅] superlattices have been studied by CEMS and time dependent nuclear resonance scattering in grazing incidence Bragg reflection geometry. CEMS shows hyperfine fields (B _hf) between 33 T and 37 T. The time spectra of reflectivity allows us to separate contributions from different ⁵⁷Fe monolayers in a bilayer. Contrary to our expectations the largest field is in the center of the Fe layers. The spontaneous orientation of B _hf is along [1 1 0] in the layer plane. This revised version was published online in September 2006 with corrections to the Cover Date.     

Surface morphology of MgO (100) crystals implanted with MeV Al+ and Al2+ ions

MgO (100) single crystals are implanted with 1.50-MeV Al⁺ and 3.00-MeV Al₂ ⁺ ions at a fluence of 1×10¹⁵ Al  atoms  cm^-2 under high-vacuum conditions. The surface morphology of the substrate is measured in air using atomic force microscopy and X-ray reflectometry followed by computer-simulated spectrum analysis. The ion-irradiated areas are found to protrude to different heights on the nanometre scale. Small height differences are observed in the areas irradiated by Al⁺ and Al₂ ⁺ ions of comparable energy, dose rate and total fluence. The results indicate that protrusions are most likely caused by implantation-induced point defects (vacancies) generated in the crystal during implantation. Other possibilities for the cause of protrusions are discussed. Thermal treatment stimulates a partial recovery of the implantation damage and alters the topography of MgO surfaces. Received: 22 May 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001