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51.
52.
M. Diviš 《Physica B: Condensed Matter》2012,407(13):2524-2526
The electronic structure of R2CoIn8 (R=Y, Pr, Nd, and Dy) intermetallic compounds is calculated from first principles based on the density functional theory (DFT). The Kohn–Sham single-particle equations of the DFT are solved using two independent computational methods, namely APW+lo and FPLO. First the structural properties of Y2CoIn8 are studied. Good agreement of calculated equilibrium volume and c/a ratio with the experimental data is found. Also we minimize the forces at equilibrium volume and calculate the symmetry-free structural parameters of the space group P4/mmm for Y2CoIn8. In Y2CoIn8, the Co 3d states are almost fully occupied and situated below the Fermi level. We applied the fixed-spin-moment method and a stable paramagnetic ground state for Y2CoIn8 was found. Finally, the crystal field (CF) parameters were calculated for R=Pr, Nd and Dy from first principles. The microscopic tetragonal CF Hamiltonian was diagonalized and the obtained eigenvalues and eigenfunctions were used to predict the anisotropy of the magnetic properties of R2CoIn8 single crystals. 相似文献
53.
Physical properties of the compound TmAgGe have been investigated by means of magnetometric, transport, calorimetric as well as neutron diffraction measurements. The compound crystallizes in the hexagonal ZrNiAl-type crystal structure. The reported results indicate that the sample exhibits an antiferromagnetic ordering below . The low temperature behavior of the magnetic susceptibility and the specific heat is in good agreement with the spin-wave theory with linear dispersion relation. In addition, the magnetic structure of TmAgGe was determined by means of neutron diffraction measurements. The Tm moments are equal to 6.44(10) μB at 1.5 K and form a non-collinear magnetic structure within the basal plane. To describe this structure three different propagation vectors: , and are required. Such a spin arrangement is analyzed on the basis of group theory. 相似文献
54.
Magnetic and magnetocaloric properties of the compound Ce5Ge4 have been studied. This compound has orthorhombic Sm5Ge4-type structure (space group Pnma, no. 62) and orders ferromagnetically at ~12 K (TC). The paramagnetic Curie temperature is ~−20 K suggesting the presence of competing ferromagnetic and antiferromagnetic interactions in this compound. The magnetization does not seem to saturate even in fields of 90 kOe at 3 K consistent with the presence of competing interactions. Saturation magnetization value (extrapolated to 1/H→0) of only 0.8μB/Ce3+ is obtained compared to the free ion value of 2.14μB/Ce3+. This moment reduction in the ordered state of Ce5Ge4 could be due to partial antiferromagnetic/paramagnetic ordering of the Ce moments and may also be due to crystalline electric field effects. Magnetic entropy change near TC, calculated from the magnetization vs. field data, is found to be moderate with a maximum value of ~9 J/kg/K at ~11 K for a field change of 90 kOe. 相似文献
55.
超磁致伸缩材料及其应用研究 总被引:4,自引:0,他引:4
稀土超磁致伸缩材料是一种新型稀土功能材料.文章概述了超磁致伸缩材料(GMM)的研究历史;对比了一种实用的超磁致伸缩材料(Terfenol-D)和压电陶瓷材料(PZT)的性能;阐述了超磁致伸缩材料当前在以下两个方面取得的研究进展:(1)关于工艺方法的研究:包括直拉法、区熔法、布里奇曼法和粉末烧结、粘结等方法;(2)关于材料组分的研究:包括对Fe原子的替代研究以及开发轻稀土超磁致伸缩材料的研究.文章最后叙述了超磁致伸缩材料的应用领域,以及发展我国稀土超磁致伸缩材料的意义. 相似文献
56.
Magnetic phase transition and the corresponding magnetostriction of intermetallic compounds RMnsGe2(R=Sm,Gd)
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The temperature dependence of lattice constants a and c of intermetallic compounds RMn2Ge2 (R=Sm, Gd) is measured in the temperature range 10-800K by using the x-ray diffraction method. The magnetoelastic anomalies of lattice constants are found at the different kinds of spontaneous magnetic transitions. The transversal and longitudinal magnetostrictions of polycrystalline samples are measured in the pulse magnetic field up to 25T. In the external magnetic field there occurs a first-order field-induced antiferromagnetism-ferromagnetism transition in the Mn sublattice, which gives rise to a large magnetostriction. The magnitude of magnetostrictions is as large as 10-3. The transversal and longitudinal magnetostrictions have the same sign and are almost equal. This indicates that the magnetostriction is isotropic and mainly caused by the interlayer Mn-Mn exchange interaction. The experimental results are explained in the framework of a two-sublattice ferrimagnet with the negative exchange interaction in one of the sublattices by taking into account the lattice constant dependence of interlayer Mn-Mn exchange interaction. 相似文献
57.
Chemical Vapor Transport of Intermetallic Systems. Chemical Transport of Co5Ge3 and CoGe By means of transport reaction (900 → 700°C, Iodine as transport agent) pure Co5Ge3 or Co5Ge3 with CoGe as a by-product can be prepared. Thermodynamic calculations allow to understand the reaction semiquantitatively. 相似文献
58.
V5Al8 films (thickness about 100 nm) were deposited on sapphire substrates by RF‐sputtering and nitridated with NH3 at 600‐1250 °C (1 min) in a RTP system. The as deposited and nitridated films were investigated by ESCA (electron spectroscopy for chemical analysis), XRD (X‐ray diffraction), XRR (X‐ray reflectometry), AFM (atomic force microscopy) and SEM (scanning electron microscopy). Formation of an aluminum nitride layer at the surface and precipitation of V(Al) in the bulk was found. In the temperature regime from 600 °C to 900 °C a considerable amount of oxygen is incorporated in the aluminum nitride layer. The roughness of the surface increased with increasing temperature and at 1250 °C a partially detaching of the AlN layer could be observed. 相似文献
59.
Svilen Bobev Veronika Fritsch Joe D. Thompson 《Journal of solid state chemistry》2006,179(4):1035-1040
Two non-stoichiometric Gd compounds, GdCu5−xTrx (Tr=Al, Ga) have been synthesized from the corresponding elements by high temperature reactions in sealed tantalum containers. They crystallize in the hexagonal CaCu5-type (Pearson's symbol hP6, space group P6/mmm, No. 191) with lattice parameters determined from single-crystal X-ray diffraction at room temperature as follows: a=5.0831(10) Å; c=4.156(2) Å for GdCu3.98(4)Al1.02(4), and a=5.1025(10) Å; c=4.155(2) Å for GdCu3.9(1)Ga1.1(1), respectively. Structure refinements from single crystal X-ray diffraction data reveal that substitution of Cu for Al or Ga takes place preferably on one of the two transition metal sites with site symmetry mmm (3g). Both compounds order antiferromagnetically below ∼40 K and ∼36 K, respectively, as determined from temperature dependent dc-magnetization, resistivity and heat-capacity measurements. 相似文献
60.
The magnetic data of RE2MnGe6 (RE = La, Ce) and YMn0.3Ge2 are reported. La2MnGe6 and Ce2MnGe6 crystallize in the orthorhombic Ce2CuGe6 structure type, space group Amm2 (No. 38). The non-stoichiometric YMn0.3Ge2 compound crystallizes with the orthorhombic CeNiSi2-type structure (space group Cmcm (No. 36)). The studied RE2MnGe6 (RE = La, Ce) intermetallics are characterized by ferromagnetic properties with Curie temperatures 177 (La) and 150 K (Ce), respectively. For YMn0.3Ge2 the low-field magnetic measurements indicate the antiferromagnetic property below 395 K with the small ferromagnetic component. The values of the magnetic moments in the ordered state indicate the ferromagnetic ordering in La2MnGe6 and complex magnetic order with the ferromagnetic component in YMn0.3Ge2 and Ce2MnGe6. The hysteresis loop and values of the coercivity field indicate that these compounds are soft magnetic materials. 相似文献