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1.
Off-stoichiometric Ni-Mn-Ga alloys, with various chemical compositions, were produced by melt-spinning technique. Transformation behavior was studied by means of differential scanning calorimetery (DSC). Ribbons and bulks reveal reversible martensitic transformation which occurs, dependently on chemical composition, in the range of temperatures: between 100°C and -150°C. Transmission electron microscope and X-ray diffractometer were used for structure examination. Dependently on chemical composition five-layered (10 M) or seven-layered (14 M) martensite was observed, whereas the parent phase shows the B2 structure. Due to high cooling rate realized in melt-spinning technique some amount of amorphous phase was found. For all ribbons magnetization was measured versus change of temperature as well as magnetic field. Due to relatively high density of dislocations lower value of magnetization were obtained.  相似文献   

2.
This paper reports structural and magnetic properties of rapidly quenched Co64Fe4Ni2B19−xSi8Cr3Alx (x=0, 1, 2, 3) amorphous ribbons prepared by the single roller melt spinning process. Thermal analysis of the ribbons shows that the replacement of B by Al causes a decrease in the crystallization temperature. Structural studies of the samples have been carried out by transmission electron microscopy and X-ray diffraction. With optimum amount of Al in the alloy, the as-cast material has better soft magnetic properties. The highest maximum permeability (3.55×105), saturation magnetization (523.7 mT) and the lowest coercivity (0.8174 A/m) were obtained in the sample with x=2.  相似文献   

3.
The effect of annealing on the magnetic and electrical properties and structural state of iron-based melt-spun ribbons was investigated. A comparative analys is of the behavior of specimens during their amorphous-to-crystalline transition revealed differences between their structural relaxation scenarios at the level of atomic ordering; the value and sign of the temperature coefficient of resistance; and the remagnetization processes, depending on the initial store of nonequilibrium.  相似文献   

4.
Amorphous Fe80ErxB20-x ribbons (0Erbium sublattice has a cone spin structure and iron sublattice is probably close to collinear.  相似文献   

5.
Fe-30%Pd alloys in ribbon and nanowire geometry have been prepared. Ribbon samples were produced by the melt-spinning technique in the Ar environment. FePd nanowires, having about 35 nm in diameter, 105 nm inter-nanowires distance and around 4 μm in length, were synthesized into nanoporous anodic alumina membranes as templates. Energy dispersive X-ray microanalysis of ribbons shows an average atomic composition of Fe (73.2%) and Pd (26.8%). The X-ray diffraction at RT analysis was performed on both surfaces, free and wheel side, of the melt-spun ribbon. It shows the coexistence of two phases: fct and bct FePd, but with differences between both surfaces consisting the existence of Fe oxides (Fe2O3 and Fe3O4) and a textured 200 reflection in the free side. Heating and cooling thermomagnetic curves exhibit a reversible behaviour from RT to 720 K, but around 770 K a clear irreversible transformation takes place.  相似文献   

6.
甩带Fe85Ga15合金的巨磁致伸缩研究   总被引:6,自引:0,他引:6       下载免费PDF全文
利用甩带快淬方法制备了Fe85Ga1 5合金样品 .测量了样品在沿带片长度方向和厚度方向上的磁致伸缩 ,发现其值分别高达 - 1 30 0ppm和 1 1 0 0ppm .巨大磁致伸缩的获得来源于甩带样品的形状各向异性和合金内部生成的大量短程应变有序以及它们的择优取向 .样品温度特性的测量表明 ,在室温附近约 6 0℃宽的温度范围 ,合金的磁致伸缩数值基本保持不变 ;而在高温条件下 ,合金具有更大的磁致伸缩  相似文献   

7.
Giant magnetoresistance (GMR) has been observed in Co5Cu95 alloys fabricated by melt-spinning. The highest MR change of 28.0% occurs for Co5Cu95 after annealing at 450°C for 30 min. Based on the super-paramagnetic assumption, the average size of Co particles embedded in Cu matrix, ranging from 3.0 to 6.0 nm, has been determined by simulating the magnetization curves at 295 K which is higher than the blocking temperatures for the samples. Comparison with phenomenological theory for GMR indicates that the interfacial spin-dependent scattering is the dominant scattering mechanism underlying GMR origin in granular systems. Additionally, for the samples in as-quenched state or annealed at temperatureT A=350°C, the electron hybridization and super-paramagnetic behaviors of fine Co particles may be responsible for the low value of MR change.  相似文献   

8.
A hybrid structure composed of ordered C11b Ti2Ni and Ti5Ni3 substructures for the G-P zones precipitated in Ti-rich Ti–Ni shape memory ribbons is proposed to explain the appearance of extra diffuse scattering streaks in transmission electron microscopy observations. The point defects of Ni vacancies and Ti antisites, resulting in the lattice fluctuant displacement, also cause the incommensurate extra diffuse scattering streaks.  相似文献   

9.
Cu-Mn-Al melt-spun ribbons of two compositions were studied to find out the influence of the collective behavior of diluted ferromagnetic nanoparticles on magnetotransport properties. The sample with a lower volume percentage of particles demonstrates magnetic behavior characteristic for the superparamagnetic state while the other one demonstrates ferromagnetic-like ordering. It is shown that the collective behavior of the system in both ribbons correlates with the temperature dependence of magnetoresistance.  相似文献   

10.
11.
Rapidly quenched (Co95Fe5)1-xAlx ribbons are investigated by X‐ray diffraction, magnetization, and Mössbauer effect measurements. A single fcc phase is obtained for all ribbons x ? 10 at.%. The lattice constant increases linearly with x and is discussed in connection with magnetic moment. The influence of Al substitution on both magnetization and Fe‐atom hyperfine field (H) is studied. At 296 K, the magnetization decreases linearly while H drops nonlinearly as x increases. Al substitution leads to substantial differences in iron hyperfine fields in bcc and fcc systems. Fe moment is perturbed differently by Al substitution in fcc (Co95Fe5)1-xAlx and bcc Fe–Al systems.  相似文献   

12.
杨白  沈保根  赵同云  孙继荣 《物理学报》2007,56(6):3527-3532
采用快淬方法制备了纳米晶复合Pr2Fe14B/α-Fe永磁薄带,研究了不同淬火速率对薄带织构和磁性的影响.通过改善快淬工艺,使得薄带中Pr2Fe14B相的晶粒在薄带的自由面形成显著的织构,Pr2Fe14B相晶粒易轴沿垂直于带面方向取向.分析了快淬凝固过程中Pr2Fe14B相的晶粒取向过程和机理,以及晶粒的大小和薄带结构的均匀性对薄带磁性的影响.对自由面有显著取向的薄带,进行酸蚀和打磨减薄处理,去除贴辊面未取向的部分,剩余部分为具有Pr2Fe14B相晶粒取向的各向异性薄带,Pr2Fe14B相取向使薄带的剩磁得到增强,矫顽力也有所提高. 关键词: 快淬 2Fe14B/α-Fe永磁薄带')" href="#">纳米晶复合Pr2Fe14B/α-Fe永磁薄带 织构 磁性能  相似文献   

13.
In this paper we investigate the surface magnetic properties of as-quenched (AQ) CoFeCrBSi ribbons prepared by planar flow casting method with using magneto-optic Kerr effect (MOKE). Measured hysteresis loops in longitudinal and transversal configurations enable us to obtain the information of ribbons surface magnetic properties. Moreover, we suggest new magneto-optic method, which is based on measurements of magneto-optical effects depending on DC current flowing through the ribbon. Experimental data of AQ ribbons are then compared with the model, which describes the influence of incidence angle on magneto-optical angles.  相似文献   

14.
We theoretically study the electronic states in graphene ribbons which are strongly affected by the edge states, the peculiar non-bonding molecular orbitals localized along the zigzag edges of the ribbons. New kinds of edge localized electronic states with spin and charge polarizations are found in the mean field solutions of the extended Hubbard model with onsite and nearest-neighbor Coulomb repulsions. These novel states appear due to the interplay between the edge states and the Fermi instabilities. We also examine the competition between the charge polarized state and the spin polarized state to draw a phase diagram depending on Coulomb parameters. The results obtained by the mean field calculations with the extended Hubbard model modified to include Coulomb integrals provide useful insights to understand and functionalize the nanoscale materials.  相似文献   

15.
Pulsed laser deposition of 250-nm thick, amorphous Dy2Fe14B layers on 40-μm thick Nd2Fe14B melt-spun ribbons was conducted to improve coercivity and energy product. The coated ribbons were subsequently annealed by two methods: (1) furnace annealing in an inert-gas controlled quartz furnace using tantalum foil at 1173 K for 2 h; (2) laser annealing using a continuous wave CO2 laser with power varying from 10 to 20 W for 0.2 s (estimated temperatures using a thermal model were 993-1528 K). X-ray diffraction was used to identify the microstructural phases and grain size. Magnetic hysteresis tests were conducted at 300 K using a SQUID magnetometer with a maximum field of 5.0 T. Results showed a 10% increase in coercivity and 30% increase in energy product in coated over uncoated samples that were furnace-annealed. However, the coated and laser-annealed samples exhibited soft magnetic behavior with almost zero coercivity. The incomplete crystallization of amorphous phase and precipitation of α-Fe during laser annealing are found to be responsible for the observation of poor magnetic performance.  相似文献   

16.
The magnetic behavior of rapidly solidified FePrB was investigated in the composition range Fe77+χPr15B8−χ (0 ≤ χ ≤ 4). Furthermore, the magnetic and microstructural properties of Fe(NdPr)B were analyzed in the range Fe78(NdχPr1−χ)15B7 (0 ≤ χ ≤ 1). The temperature dependence of the critical field was analyzed with a modified form of Brown's expression for the nucleation field. From this analysis the values for the microstructural parameters, K and Neff, were determined which describe the deteriorating effects of the non-ideal microstructure on the coercivity.  相似文献   

17.
Qian Liu 《中国物理 B》2021,30(8):87502-087502
The effects of wheel speeds and high-pressure hydrogen treatment on phase evolution, microstructure, and magnetocaloric properties in La0.5Pr0.5Fe11.4Si1.6 melt-spun ribbons are studied in this work. The results reveal that the increase of wheel speed is beneficial to the formation of cubic NaZn13-type phase and the grain refinement. The optimized wheel speed for microstructural and magnetocaloric properties is 30 m/s. The largest entropy change of 18.1 J/kg·K at 190 K under a magnetic field change of 0 T-5 T is obtained in La0.5Pr0.5Fe11.4Si1.6 ribbons melt-spun at 30 m/s. After a high-pressure hydrogen treatment of 50 MPa, the Curie temperature of the ribbons prepared at 30 m/s is adjusted to about 314 K and the large -ΔSM of 17.9 J/kg·K under a magnetic field change of 0 T-5 T is achieved at room temperature with almost none hysteresis loss. The small thermal and magnetic hysteresis and the large -ΔSM make the La0.5Pr0.5Fe11.4Si1.6 hydride ribbons appropriate for magnetic refrigerant applications around room temperature.  相似文献   

18.
The structural and magnetic properties of Fe 10 at% doped SnO2 powders milled for different times have been investigated. XAS results demonstrate the dilution of Fe atoms in the rutile structure after 5 h of milling. Fe atoms have almost one oxygen vacancy near neighbour. At RT the sample presents the superposition of paramagnetic and ferromagnetic behaviours. When temperature decreases a progressive blocking process was observed. Below 100 K a field shift of hysteresis loops is evident indicating magnetic coupling between ferromagnetic/antiferromagnetic phases.  相似文献   

19.
Journal of Experimental and Theoretical Physics - We report on the results of analysis of magnetic properties and electronic structure, which were obtained by self-consistent ab initio...  相似文献   

20.
《Current Applied Physics》2018,18(11):1289-1293
The influence of crystallization treatment on the structure, magnetic properties and magnetocaloric effect of Gd71Ni29 melt-spun ribbons has been investigated in detail. Annealing of the melt-spun samples at 610 K for 30 min, a majority phase with a Fe3C-type orthorhombic structure (space group, Pnma) and a minority phase with a CrB-type orthorhombic structure (space group, Cmcm) were obtained in the amorphous matrix. The amorphous melt-spun ribbons undergo a second-order ferromagnetic to paramagnetic phase transition at 122 K. For the annealed samples, two magnetic phase transitions caused by amorphous matrix and Gd3Ni phases occur at 82 and 100 K, respectively. The maximum magnetic entropy change (–ΔSM)max is 9.0 J/(kgˑK) (5T) at 122 K for the melt-spun ribbons. The values of (–ΔSM)max in annealed ribbons are 1.0 and 5.7 J/(kgˑK), corresponding to the two adjacent magnetic transitions.  相似文献   

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