Effect of annealing on the microstructure of NiFe1.925Dy0.075O4 thin films

Dysprosium-doped nickel-ferrite (NiFe_1.925Dy_0.075O₄) thin films were fabricated using RF sputter-deposition. Structural studies indicate that the effect of post-deposition annealing is significant on structural evolution in NiFe_1.925Dy_0.075O₄ films. As-grown NiFe_1.925Dy_0.075O₄ films were amorphous. Annealing (T_a) in air at 450-1000 °C results in the formation of nanocrystalline NiFe_1.925Dy_0.075O₄ films, which crystallize in the inverse spinel structure. The average grain size (L) increases from 5 to 40 nm with increasing T_a from 450 to 1000 °C. Lattice constant of NiFe_1.925Dy_0.075O₄ films is higher compared to that of NiFe₂O₄ due to partial substitution of Dy³⁺ ions for Fe³⁺ ions. The lattice parameter increases from 8.353 to 8.362 Å with increasing T_a from 450 to 1000 °C which is attributed to the lattice-strain developed in the NiFe_1.925Dy_0.075O₄ films with increasing T_a. The corresponding density of NiFe_1.925Dy_0.075O₄ films increases from 3.2 to 3.9 g/cm³ with increasing annealing temperature. Magnetization measurements indicate the ferromagnetic behavior of all the films while the coercive field values at 300 K are found to be 0.0134 T and 0.0162 T for as grown and T_a = 1000 °C films, respectively.     

Influence of Annealing Conditions on Nanocrystalline and Ultra-Soft Magnetic Properties of Fe75.5Cu1Nb1Si13.5B9 Alloy

The magnetic and structural properties of FINEMET alloy with a composition of Fe75.5Cu1Nb1Si13.5B9 were investigated after primary and secondary crystallization of amorphous ribbon sample.The crystallization behavior and the nanocrystal formation of the samples were performed by differential thermal analysis(DTA) which in turn was supported by X-ray diffraction(XRD) study.Temperature dependence of initial permeability of amorphous and devitrified toroid shaped samples has been measured.Enhancement of Curie temperature of the amorphous alloy has been observed due to the irreversible structural relaxation.With the appearance of nanocrystalline phase the Curie temperature of the residual amorphous phase gradually decrease with the increase of annealing temperature.Their temperature dependence reflects the characteristic annealing temperature evolution of the basic magnetic parameters in these nanocrystalline systems.Saturation magnetization,Ms,increases with annealing temperature Ta for the samples and finally decreases during annealing at a temperature much higher than peak crystallization temperature.     

基于ANSYS的径向永磁轴承承载特性研究

文章介绍了径向永磁轴承的特点及结构分类,分析了影响径向永磁轴承承载特性的因素,然后对构成径向永磁轴承的磁环的装配和磁化方向进行了分析,最后利用ANSYS软件通过理论计算对轴向磁化径向永磁轴承承载特性进行了研究,为径向永磁轴承的工程应用提供了依据。     

新型节能KZ磁化装置的结构改进与应用

针对影响永磁磁化装置磁路稳定因素进行分析讨论，指出国内现有永磁式磁化器结构与使用中存在不足之处，提出了在磁化结构上提高磁化节能技术水平的关键和措施。     

废水处理新工艺在梅山烧结厂的应用

采用废水从净化站顶层集流箱流入磁凝聚器，再进入斜板沉淀池进行净化处理，净化水流进清水池循环使用，斜板沉淀池底部的污泥经螺旋输泥机推出，由脉冲气力提升器送至矿仓参加配料的工艺流程，较好地解决了烧结厂的废水处理问题，水中悬浮物去除率〉９７％，经济效益与环境效益显著。     

Magnetic and neutron diffraction studies on potassium uranate KUO3

The magnetic properties of KUO₃ with the cubic perovskite structure have been studied. It shows an antiferromagnetic-type of transition at ca. 17 K in the magnetic susceptibility vs. temperature curve. Magnetic hysteresis is observed at 4.5 K, but not observed at 20 K. Neutron diffraction measurements have been performed on the powdered KUO₃ below and above the transition temperature. The neutron diffraction pattern measured at 10 K shows no appreciable difference from that measured at 50 K. A small ordered magnetic moment of U⁵⁺ ion will make it very difficult to observe magnetic diffractions, even if a magnetic ordering occurs. If the magnetic spin alignment occurs in a small domain, no magnetic diffraction will be found in the neutron experiments. On the other hand, the magnetic phenomena of KUO₃ have been analyzed on the basis of an octahedral crystal field model.     

The effect of Co doping on the magnetic and magnetocaloric properties of Pr0.7Ca0.3Mn1−xCoxO3 manganites

In this work, we report the effect of low amount of cobalt doping at the Mn-site on the magnetic and magnetocaloric properties of Pr_0.7Ca_0.3Mn_1−xCo_xO₃ (0≤x≤0.1) powder samples. Our samples, elaborated using the solid–solid reaction method at high temperature, are single phase and crystallize in the orthorhombic system with Pnma space group. While the parent compound Pr_0.7Ca_0.3MnO₃ exhibits a charge order state at low temperature, the substituted samples with low amount of cobalt exhibit a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature T_C increases with Co content from 105 K for x=0 to 116 K for x=0.1. The maximum values of the magnetic entropy change $\left|\mathrm{\Delta }{S}_{\mathrm{M}}^{\max }\right|$ are found to be 0.8 J/kg K, 2.2 J/kg K, 3.1 J/kg K and 3.2 J/kg K in a magnetic field change of 5 T for x=0, 0.02, 0.05 and 0.1 respectively. The maximum value of the relative cooling power RCP is found to be 378.2 J/kg in the Pr_0.7Ca_0.3Mn_0.95Co_0.05O₃ at 5 T. This value of RCP is about 92% of that obtained in gadolinium metal, known as one of the most important materials for magnetic refrigeration, at the same magnetic field change of 5 T.     

Magnetic properties of R2CoGa3 (R = rare earth) compounds

R₂CoGa₃ compounds (R = Gd, Th, Dy, Ho, Er and Y) crystallize in the hexagonal P6,lmcm space group. In these compounds the Co atoms have practically no magnetic moment. The heavy rare earth compounds order ferromagnetically with relatively low Curie temperatures ( 3 K (Er) T_c 50 K (Gd)). The compounds with Tb and Dy, and to a smaller extent the Ho compound, present irreversibilities in their magnetization processes, and there are maxima in the zero-field-cooled susceptibility curves.     

铁磁性物质在地磁场中的静置磁化和退磁

介绍了铁磁性物质静置于地磁场中产生的自发磁化和退磁的原因，主要有以下三点：一是磁时效—铁磁性物质的磁性和磁畴的空间排列都滞后于施加于其上的磁化场；二是地磁场强度大小和方向随着时间推移而发生的周期性变化；三是金属的时效—材料中机械应力随着时间流逝导致其磁化曲线和金相组织的改变以及延迟裂纹的出现等。     

Morphological,structural, surface,thermal, chemical,and magnetic properties of Al-doped nanostructured copper ferrites

Aluminum-doped copper ferrite nanoparticles synthesized via thermal decomposition were analyzed for Al³⁺ substitution effects. Nanocrystalline doped copper ferrite with a crystallite size <9 nm was characterized using several advanced techniques, including X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The degree of thermal decomposition used for doping copper ferrite at the nanoparticle level correlates well with the quantitative, dimensional, and structural characterizations. The Scherrer equation and Williamson–Hall method were employed to determine the general lattice strain and constants. Structural properties, such as the oxygen positional parameters, radii of the octahedral and tetrahedral sites, hopping lengths, bond lengths and angles, site bonds, and edge lengths, were determined using XRD patterns. The improved A–B super-exchange interaction was demonstrated by the discrepancy in the theoretically anticipated bond angles. The analysis of magnetic hysteresis (M − H) using a vibrating sample magnetometer (VSM) and XPS confirmed the improvement in the super-exchange interaction. XPS results suggest that Fe and Cu in the crystal lattice are in the form of Fe^III and Cu^II, respectively. The investigation of the degree of inversion, state, and composition using XPS aids to understand the properties of the nanostructured copper ferrites. The saturation and remnant magnetization were determined from hysteresis loops at 1.8 T obtained using the VSM at room temperature. The noncollinear spin and efficient sublattice interactions are responsible for the decrease in M_s and M_r.