The domain structure and barkhausen effect in Fe<Subscript>78</Subscript>B<Subscript>12</Subscript>Si<Subscript>9</Subscript>Ni<Subscript>1</Subscript> amorphous alloy

There is no correlation between dimensions of the domain structure elements in an Fe₇₈B₁₂Si₉Ni₁ amorphous alloy ribbon and the Barkhausen effect characteristics in this alloy in various states: initial, hydrogenated, and annealed. Traditional notions of the Barkhausen effect, the nature of which is related to the domain size and the domain wall mobility, are inapplicable to disordered systems such as magnetically soft amorphous metal alloys.     

Effect of dispersion and polymeric coatings on the magnetic properties of the Fe<Subscript>73.1</Subscript>Cu<Subscript>1.0</Subscript>Nb<Subscript>3.0</Subscript>Si<Subscript>15.5</Subscript>B<Subscript>7.4</Subscript> amorphous alloy

We tested Fe_73.1Cu_1.0Nb_3.0Si_15.5B_7.4 amorphous alloy for changes in the magnetic properties accompanying the transition from the strip form into a powder and after modification with polymeric coatings. It is shown that the dispersion down to particles smaller than 10 μm in size and the procedure of modification do not, in fact, worsen the magnetic properties of the alloy.     

Effect of laser irradiation on the magnetic properties of an amorphous Fe<Subscript>73.7</Subscript>Nb<Subscript>2.4</Subscript>Cu<Subscript>1.0</Subscript>Si<Subscript>15.5</Subscript>B<Subscript>7.4</Subscript> alloy

This paper presents an experimental study of the effect of laser irradiation on the magnetic properties of an amorphous Fe_73.7Nb_2.4Cu_1.0Si_15.5B_7.4 alloy. We have measured its magnetic susceptibility and paramagnetic Curie temperature and assessed the response of the key magnetic parameters of the material to laser irradiation. The results of magnetic measurements are analyzed in conjunction with X-ray diffraction data.     

Effect of laser processing on the dynamic magnetic properties of amorphous Fe<Subscript>64</Subscript>Co<Subscript>21</Subscript>B<Subscript>15</Subscript> ribbons

We have studied the effect of laser processing conditions on the dynamic magnetic properties of amorphous Fe₆₄Co₂₁B₁₅ ribbons. The results indicate that the laser beam scan speed and direction on the sample surface relative to the axis of rolling play a key role in determining the variation of the relative dynamic magnetic permeability with magnetic field and its sensitivity to elastic tensile stress.     

Influence of wheel speed during planar flow melt spinning on the microstructure and soft magnetic properties of Fe<Subscript>68.5</Subscript>Si<Subscript>18.5</Subscript>B<Subscript>9</Subscript>Nb<Subscript>3</Subscript>Cu<Subscript>1</Subscript> ribbons

The structure and soft magnetic properties of Fe_68.5Si_18.5B₉Nb₃Cu₁ (at.%) alloy ribbons produced through planar flow melt spinning at different wheel speeds viz. 34, 17 and 12 m/s have been investigated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, vibrating sample magnetometer and positron lifetime spectroscopy. Amorphous ribbons formed with different wheel speeds manifested different enthalpy and activation energy of crystallization. The volume fraction of nanocrystalline phase, saturation magnetization and permeability are found to increase whereas coercivity is found to decrease with increasing wheel speed on annealing. A detailed analysis of positron lifetime spectra obtained from the as-spun ribbons has been used to rationalize the variation in microstructure and magnetic properties. The presence of larger number of defects at higher wheel speed increases the volume fraction of nanocrystalline phase on annealing which improves the soft magnetic properties.     

Effect of heating rate on the microstructural and magnetic properties of nanocrystalline Fe<Subscript>81</Subscript>Si<Subscript>4</Subscript>B<Subscript>12</Subscript>P<Subscript>2</Subscript>Cu<Subscript>1</Subscript> alloys

The effect of heating rate on the structural and magnetic properties of the nanocrystalline Fe₈₁Si₄B₁₂P₂Cu₁ alloy has been investigated. Amorphous Fe₈₁Si₄B₁₂P₂Cu₁ alloy was annealed at 753 K for 180 s at different heating rates ranging from 0.05 to 5 K/s in protective argon atmosphere. The structural and magnetic properties of the as-quenched and annealed alloys were studied using X-ray diffractometer (XRD), differential scanning calorimeter (DSC), vibrating sample magnetometer (VSM), and B–H loop tracer, respectively. Amorphous precursor prepared by industry-grade raw materials is obtained. The increase of heating rate is found to be significantly effective in decreasing the grain size of α-Fe(Si) phase, but the grain size increases at higher heating rate. The volume fraction of α-Fe(Si) phase shows a monotonic decrease with the increase of the heating rate. The coercivity H _c markedly decreases with increasing heating rate and exhibits a minimum at the heating rate of 0.5 K/s, while the saturation magnetization, M _s, shows a slight decrease. These results suggest that the effect of heating rate on H _c and M _s is originated from the changes of grain size and the volume fraction of α-Fe(Si) phase.     

非晶Fe78Si9B13磁粉芯的制备及性能研究

以气流磨法制备的Fe78Si9B13非晶粉末为原料成功制备了非晶磁粉芯。研究了退火温度和成型压力对磁粉芯性能的影响规律。结果表明,在低于起始晶化温度的条件下,非晶磁粉芯的损耗随退火温度的提高而先降低后增大,磁导率变化规律则相反,并在350℃时到达最佳值;成型压力增大导致磁粉芯的密度提高,对应的损耗降低,导磁率增大,并在2000MPa左右达到最大值。     

Effect of transition metal (TM) on the crystallization and the magnetic properties of Fe<Subscript>62</Subscript>Co<Subscript>10</Subscript>Si<Subscript>10</Subscript>B<Subscript>13</Subscript>Nb<Subscript>4</Subscript>TM<Subscript>1 </Subscript>melt-spun ribbons

Crystallization and magnetic behavior of melt-spun Fe₆₂Co₁₀Si₁₀B₁₃Nb₄TM₁ amorphous ribbon where TM = Ni, Cr, V, Pd, Pt, Ti, Ta and Zr were examined. The alloy with Pt as transition metal showed the lowest crystallization temperature of 823 K among the studied alloys. Significant increase in crystallization temperature was observed when the atomic radius of the substituted transition metal was varied from that of Pt. High Curie temperature and high saturation magnetization were recognized for the alloys containing Pd, Pt or Ti. The amorphous alloys except the alloys containing Ti or V showed good soft magnetic properties.     

The effect of a precursor on the magnetostatic and dynamic characteristics of Co<Subscript>68</Subscript>Fe<Subscript>4</Subscript>Cr<Subscript>4</Subscript>Si<Subscript>12</Subscript>B<Subscript>12</Subscript> amorphous ribbons

We have studied the influence of a precursor on the magnetostatic and dynamic characteristics of Co₆₈Fe₄Cr₄Si₁₂B₁₂ amorphous alloy ribbons. It is established that a rational choice of the precursor provides for a significant increase in the properties of soft magnetic ribbons and noticeably increases the magnetoimpedance.     

Fe<Subscript>73.5</Subscript>Cu<Subscript>1</Subscript>Nb<Subscript>3</Subscript>Si<Subscript>15.5</Subscript>B<Subscript>7</Subscript> Thin Films Deposited by HiPIMS: Magnetic and Magnetostrictive Behavior

Results concerning the magnetic, magnetostrictive, structural, morphological, and topological properties of amorphous and nanocrystalline Fe _73.5Cu ₁Nb ₃Si _15.5 B ₇ thin films deposited using the high power impulse magnetron sputtering (HiPIMS) technique are reported. In as-deposited state, the samples are amorphous, the nanocrystalline state being achieved for samples isothermally annealed at adequate temperatures, in an electric furnace. For the optimum annealing temperature (475 ^°C), a decrease by about 70 % for the coercive magnetic field (50 A/m) and up to 1 order of magnitude for the saturation magnetostriction (~1×10^?6), compared to the as-deposited state, was obtained. The X-ray diffractometry (XRD) and scanning electron microscopy (SEM) results for samples thermally treated at 475 ^°C revealed a 53.6 % crystalline volume fraction of α-Fe(Si) nanograins with an average size of about 15 nm and a Si content of 10.78 %, uniformly dispersed in a residual amorphous matrix. Using the saturation magnetostriction values determined using the cantilever deflection method and the crystalline volume fraction of α-Fe(Si) nanograins, the contribution of crystalline phase to the saturation magnetostriction was also determined.     

Effect of surface morphology on atmospheric corrosion behaviour of Fe-based metallic glass,Fe<Subscript>67</Subscript>Co<Subscript>18</Subscript>Si<Subscript>14</Subscript>B<Subscript>1</Subscript>

The nature of atmospheric corrosion behaviour of an as-cast metallic glass, Fe₆₇Co₁₈Si₁B₁₄ ribbon, was evaluated. The wheel side surface of the ribbon was more corroded than the air side surface, due to the higher density of air pockets present. The phases present in atmospheric rust were analysed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to be goethite, lepidocrocite, magnetite, cobalt oxide and cobalt hydroxide phases. Goethite and lepidocrocite were in amorphous form. The nature of rusting was understood by scanning electron microscopy (SEM). Nucleation of rust started at preferred locations on the surface and grew along the surface in certain directions.     

Mechanical properties of superhard boron subnitride B<Subscript>13</Subscript>N<Subscript>2</Subscript>

Microstructure and mechanical properties of bulk polycrystalline rhombohedral boron sub-nitride B₁₃N₂ synthesized by crystallization from the B–BN melt at 7 GPa have been systematically studied by micro- and nanoindentation, atomic force microscopy and scanning electron microscopy. The obtained data on hardness, elastic properties and fracture toughness clearly indicate that B₁₃N₂ belongs to a family of superhard phases and can be considered as a promising superabrasive or binder for cubic boron nitride.     

气流破碎Fe-Si-B非晶磁粉芯的制备与磁性能研究

采用粉末冶金技术,以气流破碎Fe78Si9B13非晶粉末为原料制备非晶磁粉芯。利用差示扫描量热仪、X射线衍射仪和B-H分析仪测试样品的热力学参数、相组成和磁性能,研究绝缘剂添加量和退火温度对磁粉芯磁性能的影响。结果表明,增加绝缘剂添加量可以降低磁粉芯的涡流损耗,但绝缘剂过多会降低磁导率和品质因数;去应力退火处理能有效提高磁导率和品质因数,降低磁损耗,但退火温度过高会使非晶磁粉芯晶化,导致磁性能的下降,最佳退火温度为400℃。     

Corrosion resistance of amorphous Fe<Subscript>82</Subscript>P<Subscript>16</Subscript>Si<Subscript>2</Subscript> in 0.1 M Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>

A soft-magnetic amorphous Fe-P-Si alloy prepared using ferrophosphorus waste was tested for corrosion in 0.1 M Na₂SO₄. In a nonequilibrium state, the Fe₈₂P₁₆Si₂ alloy interacts with the medium, but annealing and relaxation reduce the interaction, without influencing the magnetic properties of the alloy. The corrosion resistance of the alloy is comparable to that of Finemet (Fe-Si-B-Nb-Cu) materials.     

Crystallization behavior,mechanical properties,and corrosion resistance of an amorphous Fe<Subscript>76.5</Subscript>P<Subscript>13.6</Subscript>Si<Subscript>4.8</Subscript>Mn<Subscript>2.4</Subscript>V<Subscript>0.2</Subscript>C<Subscript>2.5</Subscript> alloy

We have studied the mechanical properties and corrosion resistance of an amorphous Fe_76.5P_13.6Si_4.8Mn_2.4V_0.2C_2.5 alloy and their response to nanocrystallization as a result of brief lamp processing and heat treatment. The results demonstrate that the lamp processing time needed to obtain a given phase composition through partial crystallization of the amorphous alloy is two orders of magnitude shorter than the corresponding heat treatment time. We have found lamp processing conditions that ensure the formation of an amorphous–nanocrystalline composite with a twofold increase in hardness, without loss of plasticity. It has been shown that, with increasing loading rate during nanoindentation, the hardness of the alloy decreases because of the increase in plasticity, which shows up as the formation of a larger number of shear bands. Under uniaxial tension, the material exhibits microplasticity, which may be due to intercluster sliding, with the amorphous structure retained. The corrosion resistance of the as-prepared amorphous alloy in a medium contaminated with sulfur dioxide exceeds that of the partially crystallized alloys.     

Inverted surface hysteresis loops in heterogeneous (nanocrystalline/amorphous) Fe<Subscript>81</Subscript>Nb<Subscript>7</Subscript>B<Subscript>12</Subscript> alloys

Inverted hysteresis loops were observed for the first time in the near-surface layers of heterogeneous (nanocrystalline/amorphous) Fe₈₁Nb₇B₁₂ alloys. In particular, a negative residual magnetization is retained when a positive magnetic field applied in the sample plane is decreased to zero. The inverted hysteresis is qualitatively explained within the framework of a two-phase model, according to which the heterogeneous alloys contain two dissimilar phases exhibiting uniaxial magnetic anisotropy and featuring antiferromagnetic exchange interaction.     

Effect of Tb substitution on the magnetic properties of exchange-biased Nd<Subscript>2</Subscript>Fe<Subscript>14</Subscript>B/Fe<Subscript>3</Subscript>B

Tb-substituted (Nd,Tb)₂Fe₁₄B/Fe₃B nanocomposite ribbons have been synthesized by melt spinning of Nd₃Tb₁Fe₇₆Cu_0.5Nb₁B_18.5 alloys. Tb substitution has significantly enhanced the value of coercivity and Curie temperature. Highest value of coercivity has been obtained as 4.76 kOe for the sample annealed at 953 K for 10 min. Curie temperature of Tb substituted sample, Nd₃Tb₁Fe₇₆Cu_0.5Nb₁B_18.5 is 549 K while Curie temperature of the sample without Tb, Nd₄Fe₇₆Cu_0.5Nb₁B_18.5 is 535 K. Recoil hysteresis loops measured along the major demagnetization curve are steep having small recoil loop area. Temperature dependence of coercivity, remanent ratio and maximum energy product have been measured for the sample annealed at 893 K and 923 K for 10 min. At 5 K, coercivity and maximum energy product of the sample annealed at 893 K for 10 min are 5.2 kOe and 11.5 MGOe respectively and the sample annealed at 923 K for 10 min are 6 kOe and 13.1 MGOe respectively.     

Fe78Si9B13非晶合金磁芯封装及其软磁性能

研究了Fe78Si9B13非晶合金磁芯进行环氧封装及封装后对非晶合金磁芯软磁性能的影响。结果表明对磁芯进行环氧封装,有效改善磁芯的机械强度同时,能改善带材表面的平整度,在带材表面形成一层绝缘层,显著降低了非晶合金磁芯高频下的损耗值,封装后的非晶合金磁芯在Bm=1T,f=1kHz下,损耗值比封装前下降了14%。综合考虑机械强度大小、磁化难易、损耗高低等因素,封装胶浓度为2%时封装效果最佳。     

Fabrication and magnetic properties of Fe<Subscript>3</Subscript>Co<Subscript>7</Subscript> alloy nanowire arrays

Fe₃Co₇ alloy nanowire arrays have been fabricated by direct current electrodeposition of Fe²⁺ and Co²⁺ into anodic aluminum oxide (AAO) templates. The phase structure and magnetic properties of the nanowires were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Magnetic measurements show that the coercivity and remanence of the as-deposited Fe₃Co₇ Alloy nanowires increase dramatically after heat-treatment at 773 K for 2 h, and the nanowire arrays exhibit uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axes owing to the large shape anisotropy. The great difference between practical coercivity and ideal coercivity was also discussed in detail.     

Two-Band Calculations on the Upper Critical Field of Sc<Subscript>2</Subscript>Fe<Subscript>3</Subscript>Si<Subscript>5</Subscript>

The ternary compound Sc₂Fe₃Si₅ has attracted much attention because of the various anomalous physical properties. The specific heat experiment and energy band structure calculation suggest that Sc₂Fe₃Si₅ is a two-gap superconductor. Based on this, we analyze the upper critical field for superconducting Sc₂Fe₃Si₅ crystals using the two-band Ginzburg-Landau theory. A two-parameter variational approach is adopted to obtain the upper critical field in arbitrary direction. The temperature and angular dependences of the upper critical field are plotted. The results reproduce the experimental data in a very broad temperature range and strongly support previous specific heat data and theoretical calculation, pointing to the existence of two energy gaps in Sc₂Fe₃Si₅. The anisotropy of the upper critical field is also studied and is about 2, in accordance with the experimental result. Moreover our calculations indicate that Sc₂Fe₃Si₅ has rather a three-dimension character, in agreement with the energy band calculation.