intermetallic compound Nd (Fe_ (1-x) Co_x) _ (10) V_2 the spin reorientation and magnetic study of microwave

　　Title: intermetallic compound Nd (Fe_ (1-x) Co_x) _ (10) V_2 the spin reorientation and magnetic study of microwave
　　Author: Liu Xin
　　Degree-granting units: Lanzhou University
　　Keywords: high-frequency magnetic: 5340, spin reorientation: 3715, Fe: 2979, Nd: 2967, V_2: 2967, x) Co_x: 2967, the easy magnetization direction: 2870, imaginary part of permeability: 1846, Magnetic : 1514, plane anisotropy: 1346, atomic radius: 1260, complex permeability: 1175, Magnetic measurements: 1057, atom: 826, anisotropy field: 699, Mossbauer spectrum: 638, intermetallic compounds : 521, lattice: 486, vibrating sample magnetometer: 478, atomic spacing: 458
　　Abstract:
　　Traditional high-frequency magnetic initial Rare earth magnets permeability and resonance frequency of the product to comply with Snoek limit, gradually difficult to meet the higher frequency of material requirements. This paper presents a planar anisotropy of rare-earth-3d transition metal intermetallic particles is expected to exceed Snoek limit, with high-plane anisotropy field and lower-plane anisotropy field of rare earth-3d intermetallic compounds can be greatly improved material permeability, while the resonance frequency remains at a high range.
　　To V is stable elements, Co as an alternative element, vacuum arc melting and vacuum heat treatment alternatives with different Co content were prepared by the 1:12-type compounds of rare earth iron metals between samples. Powder samples at room temperature and then use the X-ray diffraction, vibrating sample magnetometer and other experimental methods of structure and magnetic properties of these compounds have been studied. Mixed with paraffin on the powder samples made of composite materials, the use of coaxial high-frequency performance of the method of its measurement and analysis. Analysis of Co and Fe elements of an alternative to the intermetallic structure and magnetic and magnetic anisotropy and high frequency magnetic properties, and discussed the impact of the magnetic anisotropy of the high-frequency and high frequency complex permeability rate mechanism. The following conclusions:
　　(1) of the compounds found in the x = 0-0.5 range, can be a single ThMn12-type structure of pure phase. With the substitution of Co atoms increases, Nd (Fe1-xCox) 10V2 lattice constant monotonically decreases, cell volume contraction, which is due to Co atomic radius smaller than the radius of Fe atoms caused.
　　(2) With the substitution of Co atoms increases, Nd (Fe1-xCox) 10V2 saturation magnetization by the 115emu / g (x = 0) to 122 emu / g (x = 0.2), then reduced to 96 emu / g (x = 0.5); the coercivity first decreases and then increases; samples the easy magnetization direction from parallel to the c-axis (x = 0) into a parallel to the ab plane (x = 0.2), the Co Atomic content further increases, the easy magnetization direction parallel to the c-axis tends again (x = 0.5). (3) With the substitution of Co atoms increases, Nd (Fe1-xCox) 10V2 Curie temperature from 570 K (x = 0), monotone to 676 K (x = 0.4), but continue to increase when the Co content , the Curie temperature down to 662 K (x = 0.5). This is because the Co atoms occupy the first atomic spacing smaller 8f and 8j positions, making the Fe-Fe decreased negative interactions, 3d sublattice enhance the overall interaction, thereby increasing the Curie temperature.
　　(4) With the substitution of Co atoms increases, Nd (Fe1-xCox) 10V2 of the spin reorientation temperature changes, the room temperature below the spin reorientation temperature from 120 K (x = 0) increasing to 280K (x = 0.4). At room temperature and above, when there is no incorporation of Co atoms at (x = 0), measuring changes in temperature until the Curie point of no spin reorientation phenomenon. But after the incorporation of Co atoms, the emergence of the phenomenon of spin reorientation and spin reorientation temperature increases with rising Co content until x = 0.5, the spin reorientation temperature decreases, but the spin orientation of the easy magnetization direction occurs, the change has been different from previous changes. This shows that the rare-earth sublattice in the Fe sublattice and gradually dominated the competition, Co atoms replace Fe sublattice anisotropy makes less.
　　(5) by Mossbauer measurements, you can see the character of V atoms occupy the 8i priority position. But the Co atoms replace Fe atoms into the lattice after, Nd (Fe1-xCox) 10V2 in the performance of Co atoms occupy a clear merit, the beginning of the Co element into the lattice, due to the different atomic spacing and the entropy of the reasons, Co atoms preferential access to 8f and 8j positions. With the Co atoms substitute, 8i and 8j positions of the isomer with increasing the content of Co atoms is increasing, but in its basic position 8f unchanged; quadrupole splitting at x = 0 and x = 0.15 and x = 0.4 and x = 0.5 between the mutation, indicating the existence of easy magnetization direction changes.
　　(6) With the substitution of Co atoms increases, the volume ratio of 35% Nd (Fe1-xCox) 10V2 powder / paraffin composite sample of the complex permittivity and not with the frequency of significant changes, and for different Co content of the sample, the value of complex permittivity and no major changes. But the complex permeability of Co atoms with different substitution undergone significant changes: the x = 0 sample, the low permeability of 2.2, when x = 0.2, its low permeability increase of 3.2 When x = 0.5, its low permeability and reduced to 2.3; the imaginary part of permeability at x = 0 and x = 0.5, the entire measurement range without resonant peaks, and the magnetic loss is mainly by the eddy current loss contributions, but for x = 0.2-0.4 and other samples, the http://www.chinamagnets.biz/ imaginary part of permeability there is a clear resonance absorption peak, the loss is mainly caused by the natural resonance plane anisotropy contribution. This is because of its high-frequency magnetic and magnetic anisotropy of a great relationship, when the anisotropy changes, the permeability will also change. From the above experimental results can be seen with the plane anisotropy of the Nd (Fe1-xCox) 10V2 sample, with better high-frequency magnetic.
　　(7) With increasing the content of Co atoms due to Nd (Fe1-xCox) 10V2 change the magnetic anisotropy of samples, making the microwave absorption properties of the sample has undergone significant changes, according to the measured permeability and dielectric calculate the dielectric constant of different samples of easy magnetization direction of the reflection loss for the surface anisotropy of the sample (x = 0.2) than the uniaxial anisotropy of the samples with (x = 0) excellent microwave absorption properties.
　　Degree Year: 2010