Effect of heat treatment procedure on magnetic and magnetocaloric properties of Ni43Mn46In11 melt spun ribbons

The effect of heat treatment on the structural, magnetic and magnetocaloric properties of Ni₄₃Mn₄₆In₁₁ melt-spun ribbons was systematically investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), magnetic force microscope (MFM) and magnetic measurements. From the XRD studies, tetragonal and cubic phases were detected at room temperature for as-spun, quenched and slow-cooled ribbons. Furthermore, it was observed, upon annealing martensite transition temperatures increased when compared to the as-spun ribbon. To avoid magnetic hysteresis losses in the vicinity of the structural transition region, the magnetic entropy changes-ΔS _m of the investigated ribbons were evaluated from temperature-dependent magnetisation-M(T) curves on cooling for different applied magnetic fields. The maximum ΔS _m value was found to be 6.79 J kg^?1 K^?1 for the quenched ribbon in the vicinity of structural transition region for a magnetic field change of 50 kOe.     

Effect of heat treatment on the magnetic and magnetoelastic properties of cobalt ferrite

The influence of different heat treatments on the magnetic and magnetoelastic properties of highly magnetostrictive CoFe₂O₄ has been investigated. The first order cubic anisotropy coefficient, coercive field, magnetostriction and high strain sensitivity were observed to decrease as the heat treatment temperature increased. The saturation magnetization of the samples on the other hand increased with increase in heat treatment temperature. These changes were not accompanied by any observable changes in crystal structure or composition and are indicative of migration of Co²⁺ from the octahedral sites (B-sites) to the tetrahedral sites (A-sites) and Fe³⁺ from the A-sites to the B-sites of the spinel structure. Different distributions of the cations at the two distinct lattice sites can strongly affect the magnetic and magnetoelastic properties of these materials.     

Effect of technological conditions on the magnetic and magnetoresistive properties of Fe20Ni80/Fe50Mn50 films

The effect several physical and technological factors have on the magnetic and magnetoresistive properties of Fe₂₀Ni₈₀/Fe₅₀Mn₅₀ multilayers is studied. The best technological conditions for preparing films with high exchange bias fields (～30 Oe) and high anisotropy of the magnetoresistive effect (～2%) are determined.     

Effect of Ni substitution on the formability and magnetic properties of Gd_(50)Co_(50) amorphous alloy

A small amount of Ni was added into the binary Gd_(50)Co_(50) amorphous alloy to replace Gd in order to obtain ternary Co_(50)Gd_(50-x)Ni_x(x = 1, 2, and 3) amorphous alloys. Compared to the binary Gd_(50)Co_(50) amorphous alloy, the Co_(50)Gd_(50-x)Ni_x amorphous alloys show an enhanced Curie temperature(T_C) with a weakened formability. The maximum magnetic entropy change(-?S_m~(peak)) of the Co_(50)Gd_(50-x)Ni_x amorphous alloys is found to decrease with the increasing T_C.The adiabatic temperature rise(?T_(ad)) of the Co_(50)Gd_(47)Ni_3 amorphous alloy is superior to that of the Fe-based metallic glasses at room temperature. The variation of the T_C and -?S_~(peak) of the Gd_(50)Co_(50) amorphous alloy with Ni addition, and the mechanism involved, were discussed.     

Structural and magnetic properties of Co50Ni50 powder mixtures

In the present work, morphological, structural, thermal and magnetic properties of nanocrystalline Co₅₀Ni₅₀ alloy prepared by high energy planetary ball milling have been studied by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. The coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. Morphological observations indicated a narrow distribution in the particle and homogeneous shape form with mean average particle size around 130 μm². The results show that an allotropic Co transformation hcp→fcc occurs within the three first hours of milling and contrary to what expected, the Rietveld refinement method reveals the formation of two fcc solid solutions (SS): fcc Co(Ni) and Ni(Co) beside a small amount of the undissolved Co hcp. Thermal measurement, as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. Magnetic measurement indicated that the 48 h milled powders with a steady state particles size have the highest saturation (105.3 emu/g) and the lowest coercivity (34.5 Oe).     

Effect of elastoplastic deformation on the static friction force

A study was made of elastoplastic deformation In surface layers caused by normal and tangential forces. A definite relationship is shown to exist between the external friction force and elastoplastic deformation. Maximum elastoplastic deformation arises in the contact zone when static friction is replaced by moving friction. The maximum elastoplastic deformation corresponds to the static friction force.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 34–37, September, 1969.     

Ni掺杂对ZnO磁光性能的影响

在掺杂浓度范围为2.78%—6.25%(物质的量分数)时,Ni掺杂ZnO体系吸收光谱分布的实验结果存在争议,目前仍然没有合理的理论解释.为了解决存在的争议,在电子自旋极化状态下,采用密度泛函理论框架下的第一性原理平面波超软赝势方法,构建不同Ni掺杂量的ZnO超胞模型,分别对模型进行几何结构优化和能量计算.结果表明,Ni掺杂量越大,形成能越高,掺杂越难,体系稳定性越低,掺杂体系带隙越窄,吸收光谱红移越显著.采用LDA(局域密度近似)+U方法调整带隙.结果表明,掺杂体系的铁磁性居里温度能够达到室温以上,磁矩来源于p-d态杂化电子交换作用.Ni掺杂量越高,掺杂体系的磁矩越小.另外还发现Ni原子在ZnO中间隙掺杂时,掺杂体系在紫外光和可见光区的吸收光谱发生蓝移现象.     

Effect of annealing on the magnetic and magnetooptical properties of Ni films

The magnetic and magnetooptical properties of 50-to 200-nm-thick Ni films, both as-deposited and annealed at T_ann = 300, 400, or 500°C, were studied. Volume and near-surface hysteresis loops were measured with a vibrating-sample magnetometer (VSM) and with the use of the transverse Kerr effect (TKE). The annealing temperature was found to exert a strong effect on the magnetic characteristics of the samples under study. It was established, in particular, that the coercivity H _C of Ni films increases and the remanent magnetization decreases with increasing annealing temperature. The observed dependences of the magnetic properties of the films on film thickness and annealing temperature are explained as being due to microstructural characteristics of the samples. It was found that, while TKE spectra obtained in the incident-photon energy region from 1.5 to 6 eV have the same shape for all the Ni films studied, the magnitude of the TKE decreases with increasing T_ann. This experimental observation is accounted for by the decreased saturation magnetization of the annealed films.     

Effect of megaplastic deformation on the magnetic properties of FeNi alloy

The effect megaplastic deformation has on the coercivity and specific saturation magnetization of soft-magnetic equiatomic FeNi alloy is studied at room temperature in a Bridgman chamber by means of X-ray diffraction, Mössbauer spectroscopy and magnetometry. Structural features responsible for changes in the alloy’s properties at different stages of deformation are revealed.     

粉末粒度离散性对NdFeB磁性能的影响

制备了一种NdFeB永磁材料,探讨了制粉前处理方式对粉末离散性、粒径及成品NdFeB永磁体结构与性能的影响。原材料经熔炼、粗破碎后,采用高速风选和高压氢爆2种制粉前处理方式,然后采用同样的成型、烧结和回火工艺制备得到(PrNd)32.3Nb0.70Al0.60Cu0.20B1.03Fe65.17合金,并系统研究了该合金的显微结构和磁性能。结果表明:高压氢爆处理后得到的粉末粒度呈单分散性,粉末粒径较细,所制备得到的磁体样品的微观结构均匀性也较好;高压氢爆处理后制得的磁体样品剩余磁通密度比高速风选制粉方式得到的磁体样品高0.047 T,内禀矫顽力高 193.4 kAm－1,最大磁能积高24.6 kJm－３。     

粉末粒度离散性对NdFeB磁性能的影响

制备了一种NdFeB永磁材料,探讨了制粉前处理方式对粉末离散性、粒径及成品NdFeB永磁体结构与性能的影响。原材料经熔炼、粗破碎后,采用高速风选和高压氢爆2种制粉前处理方式,然后采用同样的成型、烧结和回火工艺制备得到(PrNd)32.3Nb0.70Al0.60Cu0.20B1.03Fe65.17合金,并系统研究了该合金的显微结构和磁性能。结果表明:高压氢爆处理后得到的粉末粒度呈单分散性,粉末粒径较细,所制备得到的磁体样品的微观结构均匀性也较好;高压氢爆处理后制得的磁体样品剩余磁通密度比高速风选制粉方式得到的磁体样品高0.047 T,内禀矫顽力高 193.4 kAm－1,最大磁能积高24.6 kJm－３。     

Effect of Ni doping on the structural and magnetic properties of FePt nanoparticles

A serial of FePtNi nanoparticles were investigated on their crystal structure and magnetic properties. The FePtNi nanoparticles were synthesized simultaneously by the reduction of iron (III) acetylacetonate, platinum (II) acetylacetonate and nickel (II) acetylacetonate with 1,2-hexadecanediol as the reducing agent. The X-ray diffraction patterns indicate that the addition of 8, 12, 17 at% Ni in FePt nanoparticles suppressed the transformation of the particles from disorder face-centered cubic to order face-centered tetragonal L1₀-phase under annealing treatment. However, further increasing Ni contents to 21 at%, the nanoparticle transformed to L1₂ phase. Doping of Ni into the FePt compound system may decrease coercivity and crystal anisotropy energy. A maximum coercivity of 7 KOe at room temperature was obtained for (Fe₅₂Pt₄₈)₉₂Ni₈ nanoparticles after annealing at 600 °C for 30 min.     

Effect of plastic deformation on phase transitions in a Ti50Ni47Fe3 alloy

The results of x-ray structural studies of the effect of previous plastic deformation by rolling on the occurrence of phase transitions in a TiNi(Fe) alloy are presented in the present work. The temperature dependences of the Bragg reflection intensities and half-widths and the dependence of the rhombic angle in the R phase with various degrees of deformation were obtained. Analysis of the results found gave the following rules. Plastic deformation substantially shifts the characteristic temperatures of the martensitic transitions (MT) R-B19′ and B19′-B19″, increases the temperature range of the transformation and can result in a “stepwise” transformation. It was observed that deformation weakly affects the temperature T_R for the B2-R transformation. Tomsk State Architecture and Construction Academy. V. D. Kuznetsov Siberian Physicotechical Institute at Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 11–20, July, 1996.     

Effect of oxidation on the magnetic properties of Ni3Cr alloy

The effect of oxidation on magnetic susceptibility and electrical resistance was studied in samples of Ni₃Cr alloy which had been prehardened from 1066, 1190, and 1250°C. X-radio-graphic analysis of the samples was carried out. It was shown that the observed increase of the magnetic susceptibility of the alloy after oxidation in the temperature range 750–1050°C is related to the formation on the surface of the sample of a layer with a variable nickel content in the range Ni₃Cr to pure nickel.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 38–41, May, 1972.     

Effect of hot deformation on texture and magnetic properties of Sm-Co and Pr-Co alloys

Nanocrystalline PrCo₅, SmCo₅ and Sm₂(Co,Fe,Mn)₁₇ alloys were subjected to a high-degree plastic deformation at 950 °C with the height reduction ranging from 70% to 95%. With increasing degree of deformation, the PrCo₅ and SmCo₅ magnets showed improvement of the deformation-induced [0 0 1] texture. The PrCo₅ alloys, known to develop a superior texture at the lower degrees of deformation, showed only modest improvement and their magnetic performance was undermined by a low coercivity. The SmCo₅ alloys had their texture markedly enhanced and, after height reduction by 94.5%, they exhibited a remanence of 8.6 kG, maximum energy product of 18 MGOe and an intrinsic coercivity of 22.8 kOe. No induced texture was found in the alloys based on the Sm₂Co₁₇ structure. The microstructures of the hot-deformed alloys were studied with a transmission electron microscopy, and possible mechanisms of the texture development in the RCo₅ alloys (R=Pr, Sm) are briefly discussed.     

Body-centered-cubic Ni and its magnetic properties

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.     

Mo nanocrystallite effects on nanostructural properties of stainless steel

Mechanical properties of stainless steel can be improved by grain size refinement down to nanocrystalline structures. In the present work, the effects of Mo nanoparticles on stainless steel powders synthesized using the sol-gel method have been studied. The results show that decreasing of the size of Mo crystallites in stainless steel is accompanied by phase transformations as well as the mesoporous surface area and narrow pore size distribution. The structure of the synthesized sample was investigated by XRD (X-ray diffraction), AFM (atomic force microscopy) and SEM (scanning electron microscopy) technologies. As revealed in AFM, SEM images and XRD patterns, worm-like pores were formed and ordered to some extent. The influence of various conditions on the structure of ordered mesoporous stainless steel is also discussed.     

Cu对Ni50Mn36In14相变和磁性的影响冰

文章研究了Cu替代部分Ni对铁磁性形状记忆合金Ni50Mn36In14相变和磁性的影响规律．研究表明,在Ni50-χcCuχMn36In14中,随着Cu含量的增加,相变温度逐渐降低．Cu含量低于5％时。奥氏体的磁性强于马氏体的磁性,母相和马氏体相的饱和磁化强度的差值△M随着Cu含量的增加而增大．当Cu含量χ=4．5时,△M迅速增加到80emu／g,并在该材料中观察到了磁场驱动的马氏体到奥氏体的转变,显示了该材料作为磁驱动磁电阻材料的潜在应用前景．当Cu含量高于5％时,奥氏体保持铁磁状态,马氏体相由反铁磁状态变为铁磁状态,马氏体的磁性强于奥氏体的磁性,△M大大削弱,磁场驱动性质消失．