Description of the process of magnetization of hollow cylindrical rods from soft magnetic materials in a homogeneous quasi-static magnetic field of a solenoid. Hysteresis loop

On the basis of the arctangential approximation of the magnetic hysteresis loop of the material and the expression for the central demagnetization coefficient of hollow cylindrical rods from soft magnetic materials, a method for calculating the hysteresis loops of these rods in a homogeneous quasi-static field of a solenoid is proposed. Calculation and comparison to experimental data of the basic parameters of the magnetic loops hysteresis of hollow cylindrical rods with a different value of the demagnetization coefficient have been made. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 181–188, November–December, 2007.     

Structure and stability of SmCo5

The structure of SmCo5has been investigated between 500°C and its melting point. It is found that SmCo5is a composite of two phases. One of them is unstable and decomposes below 1150°C giving rise to the neighboring phase Sm2Co17. No traces of Sm2Co7have been observed during this decomposition. The reaction of SmCo5with the container materials is discussed. The potential importance of RCo5compounds of the CaZn5- type structure for the manufacture of permanent magnets has resulted in intensive research on these materials. These materials have extremely high energy products and coercive fields. Several reports on the structure and stability of SmCo5have been presented in recent years. On the basis of measurements of the coercive field, Westendorp [1,2] concludes that SmCo5is a single phase above 1080°C and below this temperature a second phase precipitates out. The size of the particles of this precipitated phase controls the coercive field. Den Broeder et al. [3] and Buschow [4] have reported a eutectoid decomposition of SmCo5at about 750°C (SmCo5= Sm2Co7+ Sm2Co17). Although they detect the presence of Sm2Co7and Sm2Co17by metallographic methods, they are unable to find any traces of Sm2Co7by X-ray diffraction techniques. In this paper we report on the structure and stability of SmCo5at various temperatures and its reaction with various container materials.     

Physical metallurgy and magnetic measurements of SmCo5-SmCu5alloys

The magnetic properties of the hexagonal intermetallic compounds involving the rare-earth and3dtransition metals have been reported in the literature. These alloys look promising as fine-particle permanent magnets. A large number of samples in the system SmCo5-xCuxwere prepared by induction melting under a protective atmosphere, and annealed at various temperatures. An outstanding feature of these alloys is their high intrinsic coercive force. After annealing at low temperatures, they show coercive forces above 20 kOe and an energy product of about 8 × 10⁶G.Oe. The most important factors determining the coercive force appear to be the chemical composition, the cooling rate, the alignment of the SmCO5-rich phase, and the annealing treatment. Examination by electron microscopy and electron probe techniques suggests a spinodal decomposition of a supersaturated solid solution into two phases, one rich in SmCo5and the other rich in SmCu5.     

Magnetic properties of thin-film Co/Fe/Ni magnetic systems

The magnetic properties of Co/Fe/Ni thin-film structures grown by magnetron sputtering have been studied using magnetooptical techniques. The results of x-ray diffraction measurements showed that all samples possessed a nanocrystalline structure. The magnetization curves and hysteresis loops were measured using the equatorial Kerr effect for two orientations of the external magnetic field. It is established that the Co/Fe/Ni thinfilm structures exhibit a planar magnetic anisotropy. The magnetic behavior of each layer in the initial inhomogeneous Co/Fe/Ni structure is substantially influenced by stray fields of the adjacent layers. This circumstance accounts for the complex shapes of hysteresis loops. The annealing in vacuum at T = 500°C renders Co/Fe/Ni thin-film structures magnetically hard compared to the initial state. The experimental results are explained by certain features of the microstructure of samples.     

The influence of surface conditions on the coercive force of SmCo5particles

The magnetic properties of single crystals of SmCo5have been studied. The spontaneous magnetization was 894 emu/cm³at room temperature. The process of magnetization reversal was extremely sensitive to the surface condition. The magnetization reversal process for spheres with rough surfaces was dominated by free wall motion, while the magnetization for spheres with the smoothest surfaces reversed by means of a jump from the completely magnetized state to the completely reversed state. These latter spheres had an energy product equal to the limiting value of(BH)_{max} = 31.6MGOe. Some preliminary data for NdCo5and YCo5are also presented.     

Effect of annealing on magnetization process of Ni3Fealloy

The magnetocrystalline anisotropy, the magnetostriction, and the structure-sensitive properties in the magnetization process were studied in the ordered-disordered states of Ni₃Fe alloy. The single crystals were cooled very slowly at the rate of 1°C/day to obtain the fully ordered state. Magnetization curves and hysteresis loops were measured using picture frame specimens. The magnetocrystalline anisotropy and the magnetostriction were also measured in disk specimens. The magnetic domain was also observed. The experimental results obtained in the ordered state are considerably different from those obtained by previous investigators. The difference is attributed to the degree of order-the magnetic properties obtained by previous investigators are those of a partially ordered state     

The observation of domain structures in SmCo5by electron microscopy

In situ observations of the domain structure of SmCo5under changing magnetic field conditions have been carried out with a high-voltage electron microscope. These observations demonstrate the existence of some pinning processes and suggest that while pinning at crystallographic defects may have some significance, that at grain boundaries may be more important. Such a view is supported by the apparent disregard of domain walls for the majority of crystallographic defects which penetrate the homogenized material and the pinning observed at a grain boundary.     

Remanence properties of substituted Ba-ferrite particles for highdensity magnetic recording

In this paper, the remanence properties of Co-Sn, Co-Ti and Co-Ti-Sn substituted Ba-ferrite (BaF) oriented particulate samples are compared with those of some oriented acicular particulate samples. A new parameter, the minor remanence distribution (MRD), is proposed to review the remanence properties of magnetic particles and the capabilities for resisting the recording demagnetization of magnetic recording media. It is shown that the MRD values of the oriented BaF particulate samples were smaller compared to oriented Co-γ-Fe₂O₃ samples, even though the squareness ratios (SR) of some of the BaF samples were smaller than those of the Co-γ-Fe₂O₃ samples. It Is the small MRD, SFD_r, IRS and large DH _r of a medium that can result in a large resistance to the effects of recording demagnetization and therefore in superior characteristics for high density magnetic recording. Since Co-Sn substituted BaF platelet-shaped particles exhibit these characteristics and have a very low temperature coefficient of coercivity, these particles can be expected to be a promising candidate for high density magnetic recording     

Effects of Biaxial Crystal Field on the Magnetic Properties on?a?Spin-1?Ising?System

Within the effective field theory (EFT) with a probability distribution technique that accounts for the self spin correlation functions, the magnetic properties such as the hysteresis loops, susceptibility and magnetization of a spin-1 Ising system with effects of a biaxial crystal field are studied. The effects of the biaxial crystal field on the magnetic properties are discussed and numerical calculations are performed and analyzed for the cases of the honeycomb lattice. A number of interesting phenomena such as the shape of the hysteresis loops and the susceptibility have been found.     

Magnetic anisotropies in single and multilayered thin films grownby bowed-substrate sputtering

Thin-film structures composed of nearly nonmagnetostrictive single-layer Co₇₆Fe₄B₂₀ or magnetostrictive Fe₈₀B₂₀ and Co₇₅Si₁₅B₁₀ amorphous layers have been deposited on bowed glass substrates using the RF-sputtering technique. The fabrication procedure induces a postdeposition compressive stress in the thin-film structure when the sample is retrieved from an arching device in the sputtering chamber. This results in an induced magneto-elastic anisotropy that governs the magnetic easy axis of the film, depending on the sign of the magnetostriction constant of each layer. Particular attention is paid here to heterogeneous structures made of bi- or multilayers with magnetic easy axis oriented in a different direction in each layer. Bulk magnetic properties were evaluated from hysteresis loops and thermomagnetization measured by vibrating sample magnetometry (VSM) and quantum interference device (SQUID) magnetometry. Magnetic domain walls and out-of-plane magnetized domains were observed by a Kerr imaging system and magnetic force microscopy. The combination of microstructure and strains induced in the layers determines the orientation of the observed magnetic anisotropies, which vary from high in-plane anisotropies up to out-of-plane orientations for selected films. The results, which provide reassurance that effective anisotropies are induced in each of the layers, are discussed in terms of the interactions between magnetic phases with different induced easy magnetization axes     

Study of a microwave ferrite resonator antenna, based on a ferrimagnetic composite (Gd3Fe5O12)GdIGX-(Y3Fe5O12)YIG1-X

The authors report a study on microwave properties of a ferrimagnetic ceramic composite (Gd₃Fe₅O₁₂)GdIG_X-(Y₃Fe₅O₁₂)YIG_1-X. The magnetic and dielectric measurements at microwave frequency were made through the Hakki?Coleman?s procedure and through the excitation of a cylindrical ferrite resonator antenna (FRA). The hysteresis loops of the GdIG_XYIG_1-X ferrimagnetic composite were obtained. The numerical simulation study was performed using Ansoft?s High Frequency Structure Simulator (HFSS) software. The agreement between the experimental data and the simulated results is very good. These results demonstrated that, by varying the material composition of the resonator, ferrimagnetic composite GdIG_XYIG_1-X could operate as a magneto-dielectric antenna with bandwidth in the range of 7.5--11% and in the frequency range of 4.4--5.3 GHz. Additionally, all FRAs presented a low negative value of T_f, which indicates suitability for microwave applications such as mobile communication systems or satellite broadcast systems.     

Nd_2Fe_(14)B/α-Fe交换耦合双层薄膜磁性能

利用微磁学理论模拟计算了Nd2Fe14B/α-Fe交换耦合双层膜的磁滞回线,并对双层膜体系的剩磁、矫顽力、最大磁能积与软磁层厚度的关系进行了研究。结果显示,软磁层厚度小于临近尺寸时,磁滞回线为矩形,双层膜完全耦合;软磁层厚度与磁性能的关系表明,随着软磁层厚度的增加,剩磁和最大磁能积先增大后减小,而矫顽力单调下降。     

Analysis of Minor Hysteresis Loops of Cold Rolled Low Carbon Steel

Minor hysteresis loops of cold rolled low carbon steel have been analyzed in connection with the rolling reduction. We found several simple relations between parameters of minor loops and obtained minor-loop properties that are independent of magnetic field amplitude and magnetic field. The properties increase with increasing rolling reduction and are in proportion to coercive force of the major loop. The present analysis method using minor loops can be applied to quantitative nondestructive evaluation of dislocation density in ferromagnetic materials     

Rayleigh hysteresis--A new look at an old law

Experimental evidence is cited that, for very small hysteresis loops, the remanent magnetic flux density Bris not proportional to the square of the amplitude of the magnetic field excursion H1(as given by the Rayleigh relation), but rather to the first power. It is shown that (subject to one very general assumption), were this dependence exact, it would lead to negative hysteresis loss. It is also shown that (subject to the same assumption) any power-series dependence ofBonHwill always giveB_{r} propto Hmin{1}max{2}. An approximate first-power dependence is found to follow naturally from the spring model. A new Rayleigh relation is proposed which contains a logarithmic term which may not be expanded in a power series about zero argument.     

Integrated On-line Instrumentation System of Magnetic Properties Measurement

1. IntroductionA magnetic inspect system has been developed formeasuremellt of the magnetic properties of soft magnetic materials. Measurements are all made underon-line computer control using a standard IBM notebook computer. The magnetic field is controlled usingan analog output line from the control and data acquisition system, which operates a bipolar power supply.The properties measured by the system are all struture sensitive and consequently the system has beenused in the nondestructi…     

Magnetic properties and critical currents of epitaxial YBa2Cu3O7-x films

The authors report results of magnetic and transport measurements on thin epitaxial films of YBa₂Cu₃O_7-x which show critical current densities of 10⁷ A/cm² at 4.2 K. They exhibit well-formed symmetrical hysteresis loops and flux-trapping effects and linear susceptibilities at low fields. Magnetic and transport critical currents are in good agreement at low temperatures. The above properties are attributed to strong pinning from point defects which are suggested to be more numerous in films than in bulk single crystals. Diamagnetic shielding effects can be very large and are proportional to the critical current at zero field; however, there is a large penetration of H_a at all field values. Field-cooled magnetization is always very small, being only a few percent of the diamagnetic shielding. This small value is attributed to a balance between trapped flux and expelled flux in the cooling process. The strong pinning in attributed to a high density of defects in the film     

Magnetic measurements on single acicular particles of γFe2O3

Measurements of the remanent coercive force Hrhave been made upon large numbers of individual 'tape' particles of γFe2O3. The greatest range of values of Hrsound for any one sample was 300r<1100 0e, and other samples of different origins gave rather similar results. Using the data for two sets of samples, together with other known factors, the remanent loops of the corresponding tapes were synthesized. The synthesized loops resembled the experimental loops, but the remanent coercive forces were larger by 20 to 60 0e: very good agreement was obtained for one sample. The effect of a.c. demagnetization was investigated. This showed that particles of the highest Hrwere undoubtedly single, but that many of lower Hrwere multiple. Particles of similar morphologies have been observed in recording tape. A value for Hrof 1100 0e is shown to be consistent with the magnetization reversing by the buckling process.     

A Low-Field Scaling Rule of Minor Hysteresis Loops in Plastically Deformed Steels

A scaling rule of magnetic minor hysteresis loops at low applied fields has been examined in plastically deformed low carbon steel and pure Ni. It was found that a power law between hysteresis loss and remanence of a minor loop holds true over the wide range of magnetization from the very low to intermediate range unlike the well-known Steinmetz law. The power-law exponent was an almost constant value of 1.35 being independent of the types of magnetic materials, the level of plastic deformation, and sample shape. The coefficient of the scaling rule increases with deformation and is in linear proportion to coercivity. This behavior was qualitatively explained on the basis of the Rayleigh law and NÉel theory.      

工业纯铁退火过程中的位错密度和磁性能EI北大核心CSCD

针对热轧工业纯铁退火过程的微观组织和磁性能,采用X射线衍射和磁滞分析法分别研究位错密度、最大磁导率、矫顽力和剩磁的演变规律。结果表明:退火前后工业纯铁的近等轴晶组织没有明显变化,晶粒度约为3.70级;随着650℃退火时间延长至5 h,位错密度从初始热轧态1.80×10^(14)m^(-2)逐渐降低至1.16×10^(14)m^(-2),降幅约35%,同时衍射峰在退火初期发生一定程度左移,并在后期明显右移,表明微观存在压应力及后续释放过程。随退火时间延长,最大磁导率整体呈上升趋势,矫顽力和剩磁存在突变点,磁滞回线形状较窄、变化不大,分析认为主要与位错密度、内应力和含碳量相关。退火处理可以改善工业纯铁的磁性能,进一步考虑成分进行一体化调控将提升工业纯铁磁性能并拓展其电磁应用空间。     

Magnetization and remagnetization of anisotrophic magnetically hard ferrites

Magnetization curves and hysteresis loops of anisotropic hard ferrites were analyzed after the specimens had been demagnetized either thermally or by an ac field parallel or perpendicular to the preferred axis (PA) between -196°C and Curie temperature, or by a dc field. Each demagnetization yields a specific magnetization curve; below saturation fields, asymmetrically positioned and noncentrosymmetrical loops develop, except after ac demagnetization at 20°C (=measuring temperature) parallel to PA. This is due to domain configurations differently arranged and of different stability. The asymmetry is caused by "frozen" unstable configurations, which undergo an irreversible change due to the action of the field. Therefore, with reversed field not all of the previous possibilities for remagnetization are still available.