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1.
Fe基非晶态合金的低温电阻研究   总被引:1,自引:0,他引:1       下载免费PDF全文
本文报道Fe100-xBx,Fe87-xSixB13,(Fe1-xCox)78Si9.5B12.5,(Fe1-xMx)80-84B16-20(M=Zr,V,Nb,Ta,Cr,Mo,W,Mn)非晶态合金的 关键词:  相似文献   

2.
研究了应用于微波频段的多层纳米颗粒膜的电阻率、软磁特性和微波磁导率.采用多次顺序沉积Co40Fe40B20和SiO2薄层制备了薄膜.在100kA/m均匀面内磁场经过250℃真空退火2h,制备的Co40Fe40B20/SiO2多层膜具有难轴矫顽力为210A/m、饱和磁化强度为838.75kA/m、电阻率为2.06×103关键词: 纳米颗粒膜 电阻率 软磁特性 微波磁导率  相似文献   

3.
The phenomenon of giant intrinsic magnetic hardness is investigated in compounds R1−x Sm x Co2Ni3 with R=Y, Pr, Gd, Tb, Er. Partial Er substitution for Sm actually increases magnetic hardness while all other substitutions decrease magnetic hardness. The strength of coercivity is thus dependent on both the sign and magnitude of the crystal field interaction. The temperature dependence of coercivity is complex in the case of Pr substitution as a result of competing effects from thermal activation and a decrease in anisotropy at low temperatures. This study has been supported by a grant from the National Science Foundation.  相似文献   

4.
Using first principle calculations the electronic structure and magnetic properties of the half metallic Co2TiGe was investigated. The electronic structure calculations were performed using two different parameterization schemes. The band gap obtained in the minority spin state using LDA scheme in TB-LMTO method was smaller than that obtained using GGA scheme in FP-LAPW method. To explore the half metallic property experimentally bulk Co2TiGe was synthesized by arc melting under argon atmosphere. The magnetic moment per formula unit determined from saturation magnetization at 2 K was 1.9 μB, which was close to the theoretically calculated value of 2 μB. A detailed analysis of the low temperature transport and magnetotransport properties exhibit characteristic features of half metals such as T9/2 dependence of low temperature resistivity, negligible temperature dependence of resistivity below 20 K and a cross over from positive to negative MR around 100 K.  相似文献   

5.
Electrical resistivity and magnetoresistivity of Ti3Ir compound have been measured in the temperature range 2.0 K ≤T ≤ 300 K in absence as well as in presence of magnetic field upto 7.7 T. The low temperature resistivity shows aT 2 behaviour whereas the high temperature resistivity shows a linear behaviour. The magnetoresistivity is positive and cannot be explained by simple s-d scattering model. The enhancement of the coefficient A of theT 2 term and the deviation from the quadratic field dependence of the resistivity may be due to the anisotropy in the compound. This work has been performed under the grant by the Department of Science and Technology, Govt. of India.  相似文献   

6.
The effect of atomic disorder on the electron transport and the magnetoresistance (MR) of Co2CrAl Heusler alloy (HA) films has been investigated. We show that Co2CrAl films with L21 order exhibit a negative value for the temperature coefficient of resistivity (TCR) in a temperature range of 10 < T < 290 K, and the temperature dependence of electric conductivity varies as T 3/2 similarly to that of the zero-gap semiconductors. The atomic or the site disorder on the way of L21 → B2 → A2 → amorphous state in Co2CrAl HA films causes the deviation from this dependence: reduction in the absolute value of TCR as well as decrease in the resistivity down to ϱ(T = 293 K) ∼ 200 μΩ cm in comparison to ϱ(T = 293 K) ∼ 230 μΩ cm typical for the Co2CrAl films with L21 order. The magnetic-field dependence of MR of the Co2CrAl films with L21 order is determined by two competing contributions: a positive Lorentz scattering and a negative s-d scattering. The atomic disorder in Co2CrAl films drastically changes MR behavior due to its strong influence on the magnetic properties.  相似文献   

7.
The magnetic hyperfine fields,B hf, for impurity119Sn atoms in Z sites of ferromagnetic Heusler alloys Co2MnZ (Z=Si, Ge) are measured by the Mössbauer effect. At 77 KB hf=–1.43±0.04 T in Co2MnSi andB hf=+1.05±0.05 T in Co2MnGe. From the comparison between the values ofB hf for Sn atoms in Co2MnZ (Z=Si, Ge, Sn), it follows that the negative contribution toB hf drops as the interatomic distance begins to increase. This radial dependence also manifests itself in the anomalies of the temperature dependences of the hyperfine fields. The temperature anomaly is positive for Sn in Co2MnGe and negative for Sn in Co2MnSi.  相似文献   

8.
The crystallographic and the magnetic structures of the composite compound Nd2Co7 at 300 K are investigated by a combined refinement of X-ray diffraction data and high-resolution neutron diffraction data. The compound crystallizes into a hexagonal Ce2Ni7-type structure and consists of alternately stacking MgZn2-type NdCo2 and CaCu5-type NdCo5 structural blocks along the c axis. A magnetic structure model with the moments of all atoms aligning along the c axis provides a satisfactory fitting to the neutron diffraction data and coincides with the easy magnetization direction revealed by the X-ray diffraction experiments on magnetically pre-aligned fine particles. The refinement results show that the derived atomic moments of the Co atoms vary in a range of 0.7 μB-1.1 μB and the atomic moment of Nd in the NdCo5 slab is close to the theoretical moment of a free trivalent Nd3+ ion, whereas the atomic moment of Nd in the NdCo2 slab is much smaller than the theoretical value for a free Nd3+ ion. The remarkable difference in the atomic moment of Nd atoms between different structural slabs at room temperature is explained in terms of the magnetic characteristics of the NdCo2 and NdCo5 compounds and the local chemical environments of the Nd atoms in different structural slabs of the Nd2Co7 compound.  相似文献   

9.
From an analysis of available data it is shown that there is experimental evidence for a rather general correlation of electrical resistivity, ϱ, and thermopower with the quasielastic linewidth of the neutron spectra, ΓQE, for intermetallic Ce- and Yb-compounds with an unstable 4f-shell. At high temperatures, kBT > ΓQE, the 4f-contribution to the resistivity, Δϱ, scales with Γ−1QE. For Ce-compounds, which show a resistivity maximum, the measured strong temperature dependence of ΓQE corresponds to the temperature dependence of the resistivity above the resistivity maximum over a few hundred K. Empirical expressions for resistivity and thermopower are presented, which not only yield the observed correlation for kBT > ΓQE, but which also describe the low temperature decrease of the two quantities: Fits for the resistivities and the thermopowers of a large number of Ce- and Yb-compounds are is very good agreement with the data over a large range of temperatures. The correlation as well as the empirical expressions for resistivity and thermopower are discussed within a model of M. Weger, which has recently been proposed to account for the so called “resistivity saturation” observed in materials with narrow bands.  相似文献   

10.
S Angappane  K Sethupathi  G Rangarajan 《Pramana》2002,58(5-6):1079-1083
We report here the low-temperature resistivity of the chemical solution deposited La1−x Ca x MnO3 (x=0.2, 0.3 and 0.33) thin films on LaAlO3 substrates. The films were post-annealed in atmosphere at 850°C. The low temperature resistivity data has been studied in order to understand the nature of low-temperature conduction processes. The data showed T 2 dependence from 60 K to 120 K consistent with the single magnon scattering process. The deviation from this quadratic temperature dependence at low temperatures is attributed to the collapse of the minority spin band. The two-magnon and electron-phonon processes contribute to scattering of carriers in the temperature range above 120 K.  相似文献   

11.
朱丹丹  章晓中  薛庆忠 《物理学报》2003,52(12):3181-3185
利用脉冲激光沉积方法在Si(100)上制备了Cox-C1-x颗粒膜,并研 究了其正磁电阻 效应.实验结果表明,样品在室温下的正磁电阻效应要远远高于低温下的正磁电阻效应;Co 0.02-C0.98样品具有最大的室温正磁电阻效应,在外加磁场B=1T时 ,其磁电阻 率MR=22%;随着Co含量的增加,Cox-C1-x颗粒膜的正磁电阻效应呈 减小趋势.样品 的MR-B的曲线与传统的多 关键词: 正磁电阻效应 x-C1-x颗粒膜')" href="#">Cox-C1-x颗粒膜 脉冲激光沉积  相似文献   

12.
We present measurements of the temperature dependence of the electrical resistivity, the thermopower and the specific heat of the hexagonal compound CeCu4Al. At high temperatures, the electrical resistivity is characterized by a nearly temperature independent behaviour, followed by a continuous increase below 100K. No maximum has been found down to 1.7 K. The thermopower shows a positive maximum at about 30 K. As in CeCu6 no negative values are observable in the range from 4.2 K up to a room temperature. The specific heat data between 7 and 15 K reveal a γ value around 280 mJ mol-1 K-2. Below this temperature range the specific heat cp/T shows a rapid rise and crosses the value of 1 J mol-1 K-2 at about 1.45 K.  相似文献   

13.
利用具有多自旋态的Co离子进行Mn位替代,制备了La2/3Ca1/3Mn1-xCoxO3 (0≤x≤0.15) 系列样品并研究了体系的结构和输运特性.结果表明,在替代范围内,样品呈现很好的单相结构,各晶格参数随替代量的增大而减小;Co替代导致体系出现电输运反常,具体表现为在居里温度TC以下电阻-温度曲线的二次金属-绝缘转 关键词: Mn位替代 双峰现象 自旋结构 磁电阻效应  相似文献   

14.
Interlayer exchange coupling in dc-magnetron sputtered Tb29.6Co70.4/FePt bilayers with different annealing temperatures of the FePt film have been investigated. The dependence of ordering degree on perpendicular magnetic properties of the FePt film was studied. The Tb29.6Co70.4/FePt film has high perpendicular coercivity and high saturated magnetization about 7.5 kOe, and 302 emu/cm3, respectively as the substrate temperature is 500 °C and annealing at 500 °C for 30 min. It also shows a strong exchange coupling between this FePt layer and Tb29.6Co70.4 layer. We also examined the interface wall energy in the exchange coupled Tb29.6Co70.4/FePt double layers.  相似文献   

15.
Superimposed asymptotic exponential relaxation between 125 and 200°C of average hyperfine inductions and their orientations were detected by the57Fe Mössbauer spectroscopy in the ferromagnetic Fe40Ni40B20 and Fe70Co10B20 amorphous alloys. From their Arrhenius type temperature dependence, average activation enthalpies ΔH were derived in agreement with the resistometric and coercivity data. The interpretation is proposed in terms of individual irreversible processes: stress relief, free volume shrinking and short-range ordering.  相似文献   

16.
By the electrospinning and calcination techniques, we have prepared uniform nanofibers of Co1−x Zn x Fe2O4 (0.0≤x≤0.5) ferrites with diameters of 110–130 nm. The Co1−x Zn x Fe2O4 nanofibers are single-phase spinels and the lattice constant with Zn content deviates from the Vegard’s law for these Co1−x Zn x Fe2O4 nanofibers. The Co1−x Zn x Fe2O4 nanocrystal grains by which are built nanofibers increase with calcination temperature. Variations of coercivity and saturation magnetization with calcination temperature can be explained in terms of the grain-size (D) effect. The coercivity (H c) of Co0.5Zn0.5Fe2O4 nanofibers varies as D 0.65 and basically follows the predicted D 2/3 dependence based on the random anisotropy model in a D range below the single-domain size around 40 nm. The saturation magnetization of Co1−x Zn x Fe2O4 nanofibers initially increases with increasing Zn content, reaches a maximum value at x=0.3 and then decreases with further increase of Zn content, while the coercivity exhibits a continuous reduction with the increase of Zn content.  相似文献   

17.
The magnetocaloric and magnetoresistance properties of amorphous Co-based (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100?xCux (x = 0, 0.5, 0.75 and 1) ribbons were investigated. Cu additions changed the crystallisation temperature (Tx) and the Curie temperature (TC). The saturation magnetisation (Ms) and coercivity (Hc) for alloys were in the range of 65.51–38.49 emu/g and 1.99–6.84 A/m, respectively. Under an applied magnetic field change of 2.2 T, the (?ΔSM)max for (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100?xCux with x = 0, 0.5, 0.75 and 1 are 0.77, 0.71, 0.89 and 0.67 Jkg?1 K?1, respectively. The values of refrigeration capacity (RC) for the as-spun glassy alloys are comparable with those of previously studied Fe-based metallic glasses such as Fe80B10Zr9Cu1, (Fe0.76B0.24)96Nb4 and Fe82Ni2Zr6B10. In addition, the maximum magnetoresistance (MR) values for (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100?xCux with x = 0, 0.5, 0.75 and 1 are found to be 110, 38, 23 and 1% around the Curie temperatures under an applied magnetic field change of 1 T, respectively. With good RC, negligible hysteresis due to very low coercivity values and large magnetoresistance, these Co-based amorphous alloys can be used as the high temperature magnetic refrigerants and multifunctional applications working in the temperature range of 450–600 K.  相似文献   

18.
The amorphous alloy Ce75.5Co24.5 prepared by melt spinning has been studied through measurements of the magnetic susceptibility, magnetization, electrical resistivity, thermoelectric power and specific heat. The results are interpreted in terms of a homogeneous intermediate valence state of the Ce ions. This is inferred from a temperature-independent magnetic susceptibility at low temperature and the absence of magnetic ordering, a large linear term in the specific heat, and aT 2 dependence of the electrical resistivity at low temperature followed by a steep increase with temperature up to 50 K. At this temperature, the thermoelectric power displays a maximum. The intrinsic properties are partially obscured at low temperatures by a contribution from roughly a few percent of magnetic impurities, presumably Ce3+ ions. They manifest themselves by an increase of the susceptibility towards low temperatures and by a broad Schottky-like contribution to the specific heat resulting from the excitation of magnetic clusters.Dedicated to Prof. Dr. S. Methfessel on the occasion of his 60th birthday  相似文献   

19.
The phenomenon of giant intrinsic magnetic hardness is investigated in compounds R1?x Sm x Co2Ni3 with R=Y, Pr, Gd, Tb, Er. Partial Er substitution for Sm actually increases magnetic hardness while all other substitutions decrease magnetic hardness. The strength of coercivity is thus dependent on both the sign and magnitude of the crystal field interaction. The temperature dependence of coercivity is complex in the case of Pr substitution as a result of competing effects from thermal activation and a decrease in anisotropy at low temperatures.  相似文献   

20.
We investigate the structure and magnetic properties of thin films of the LaCoO3 compound. Thin films are deposited by pulsed laser deposition on various substrates in order to tune the strain from compressive to tensile. Single-phase (001) oriented LaCoO3 layers were grown on all substrates despite large misfits. The tetragonal distortion of the films covers a wide range from -2% to 2.8%. Our LaCoO3 films are ferromagnetic with Curie temperature around 85 K, contrary to the bulk. The total magnetic moment is below 1μ B /Co3+, a value relatively small for an exited spin-state of the Co3+ ions, but comparable to values reported in literature. A correlation of strain states and magnetic moment of Co3+ ions in LaCoO3 thin films is observed.  相似文献   

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