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1.
The magnetization and susceptibility investigation of pseudo-binary U(Ni1?xFex)2 and U(Ni1?xCux)2 for chosen concentrations of x ? 0.1, x ? 0.8, and x ? 0.06, respectively, are presented. The most significant result is that the substitution of Ni (in UNi2) by Fe reduces both the magnetic moment and the ordering temperature rapidly although it appears to be established that the magnetic moment of UFe2 is predominantly residing on the Fe sites. The small concentration of Cu substituted into UNi2, on the other hand, increases the magnetic moment. The obtained results are discussed together with those of U(Ni1?xCox)2 and seem to support the recently proposed explanation on the origin of magnetism in UNi2.  相似文献   

2.
Mössbauer studies of R2(Fe1?x?y Ni x Co y )17 showed that the transferred hyperfine field at Fe nuclei due to magnetic rare earth (R) atoms is about one Tesla. Magnetic moments of the R atoms were determined from magnetic measurements as μTb=8.52μB, μGd=6.22μB. The mixed substitution of Ni and Co for Fe leads to an increase of the ordering temperature. A slight preference occupancy for Fe was observed involving the dumbbell shaped f or c site. The substitution effects of Ni and Co on the hyperfine field of f or c site, the average hyperfine field and the average isomer shift were also discussed.  相似文献   

3.
Y2(Fe1-x-y,Coy,Crx)17化合 物的结构及居里温度   总被引:2,自引:0,他引:2       下载免费PDF全文
郝延明  赵伟  高艳 《物理学报》2003,52(10):2612-2615
通过x射线衍射及磁测量手段研究了Y2(Fe1-y-x,Coy,C rx)17化合物的结 构及居里温度.研究结果表明Y2(Fe1-y-x,Coy,Crx)17化合物具有六 角相的Th2Ni17型结构.随着x的增加,Y2(Fe 关键词: 2(Fe1-y-x')" href="#">Y2(Fe1-y-x y')" href="#">Coy x)1 7化合物')" href="#">Crx)1 7化合物 x射线衍射 居里温度  相似文献   

4.
刘新浩  林景波  刘艳辉  金迎九 《物理学报》2011,60(10):107104-107104
利用基于密度泛函理论的全势线性缀加平面波方法,结合广义梯度近似,对full-Heusler X2YGa(X=Co,Fe,Ni;Y=V,Cr,Mn)合金的电子结构、磁性及半金属特性进行了研究,并讨论了自旋-轨道耦合作用对它们的影响.计算结果表明,自旋-轨道耦合作用对full-Heusler X2YGa(X=Co,Fe,Ni;Y=V,Cr,Mn)合金的电子结构,磁性与半金属特性的影响很小. 当未考虑自旋-轨道耦合作用时,Co2VGa,Co2CrGa,和Fe2CrGa合金为半金属或准半金属铁磁体,加入自旋-轨道耦合作用后体系的自旋极化率将降低1%左右, 它们依然保持很高的自旋极化率.Fe2MnGa,Co2MnGa,Ni2CrGa和Ni2MnGa合金为一般铁磁体,Fe2VGa和Ni2VGa合金为顺磁体. 关键词: 半金属特性 自旋-轨道耦合 Heusler合金 全势线性缀加平面波方法(FLAPW)  相似文献   

5.
Fe50Mn15-xCoxNi35(x=0,1,3,5,7)alloys were prepared by arc melting under purified argon atmosphere.The ingots were homogenized at 930°C for 90h followed by water quenching.The crystal structure,magnetic properties and magnetocaloric effects of the alloys were studied by X-ray diffraction(XRD)and MPMS-7-type SQUID.The results show that all samples still maintained a single-(Fe,Ni)-type phase structure.With the increase of the content of Co,the Curie temperatures of these alloys increased and exhibited a second-order magnetic transition from ferromagnetic(FM)to paramagnetic(PM)state near Curie temperature.The maximum magnetic entropy change and the relative cooling power of Fe50Mn10Co5Ni35alloy was 2.55 J/kg·K and 181 J/kg,respectively,for an external field change of 5T.Compared with rare earth metal Gd,Fe50Mn15-xCoxNi35 series of alloys have obvious advantage in resource price;their Curie temperatures can be tuned to near room temperature,maintain a relatively large magnetic entropy change at the same time and they are a type of potential magnetic refrigeration materials near room temperature.  相似文献   

6.
Measurements of magnetization in static fields up to 60 kOe and magnetic susceptibility in weak ac fields of the Y(Ni1−x Mx)3 and Y2(Ni1−x Mx)7 intermetallics (M=Fe and Cu, x max=0.2), as well of the specific heat of these systems for some compositions are reported. It was found that these intermetallics are ferromagnetic at low temperature, and that their spontaneous magnetizations M s at 4.2 K and Curie temperatures T C decrease monotonically with increasing copper concentration. The magnetic susceptibility of the Y(Ni1−x Fex)3 system with 0.06≲x≲0.2 was observed to decrease rapidly with the temperature lowered below a characteristic temperature T s. One of possible reasons for such an anomaly is shown to be the onset in this concentration region of the reentrant spin-glass state at low temperatures. The results obtained demonstrate that the tight-binding d-band model fails to explain the evolution of the magnetic properties of YNi3 and Y2Ni7 in the case of small substitutions of iron and copper for nickel. Fiz. Tverd. Tela (St. Petersburg) 39, 1828–1830 (October 1997)  相似文献   

7.
The synthesis of materials and the studies of crystal structure and 57Fe Mössbauer effect were performed for Tb0.27Dy0.73(Fe1?x Co x )2 intermetallics. Terfenol-D (Tb0.27Dy0.73Fe2) is the starting compound of this Fe/Co-substituted series. X-ray measurements showed evidence of a pure cubic Laves phase C15, MgCu2-type, and unit cell parameters were determined across the series. A Co substitution introduced local area, at sub-nanoscale, with random Fe/Co neighbourhoods of the 57Fe atoms.Mössbauer effect spectra for the Tb0.27Dy0.73(Fe1?x Co x )2 series at room temperature are composed of a number of locally originated subspectra due to the random distribution of Fe and Co atoms in the transition metal sublattice, and due to [1 1 1] an easy axis of magnetization. Isomer shift, magnetic hyperfine field and quadrupole interaction parameter were obtained from the spectra, both for the local area and for the bulk sample.As a result of Fe/Co substitution, a Slater-Pauling-type curve for the average magnetic hyperfine field vs. Co content was observed. It was found that the magnetic hyperfine fields corresponding to the local area also create a dependence of the Slater-Pauling-type vs. Co contribution in the Fe/Co neighbourhoods.  相似文献   

8.
Core-shell Co(1−x)NixFe2O4/polyaniline nanoparticles, where the core was Co(1−x)NixFe2O4 and the shell was polyaniline, were prepared by the combination of sol-gel process and in-situ polymerization methods. Nanoparticles were investigated by Fourier transform spectrometer, X-ray diffraction diffractometer, Scanning electron microscope, Differential thermal analysis and Superconductor quantum interference device. The results showed that the saturation magnetization of pure Co(1−x)NixFe2O4 nanoparticles were 57.57 emu/g, but Co(1−x)NixFe2O4/polyaniline composites were 37.36 emu/g. It was attributed to the lower content (15 wt%), smaller size and their uneven distribution of Co(1−x)NixFe2O4 nanoparticles in the final microsphere composites. Both Co(1−x)NixFe2O4 and PANI/Co(1−x)NixFe2O4 showed superparamagnetism.  相似文献   

9.
Magnetic measurements (temperature and field dependence) on Heusler alloys Ni2(Ti, Mn)Sn and Co2(Ti, Mn)Sn were performed in the ferro- and para-magnetic region. In both systems the composition range was from x = 0 to x = 1. All the Co2(Ti, Mn)Sn samples are ferromagnetic; in the system Ni2Ti1?xMnxSn for x ? 0.2. Our interpretation of the magnetic data differs from that of previous authors.  相似文献   

10.
Synthesis of two novel series of intermetallic compounds Tb3(Fe1−xCox)27.4V1.6 (x=0,0.1, 0.2, 0.3, 0.4) and Dy3(Fe1−xCox)27.8V1.2 (x=0, 0.1, 0.2, 0.3) with the monoclinic Nd3(Fe,Ti)29-type structure (3:29) is presented. In the Dy series for x=0.4 a disordered variant of the hexagonal Th2Ni17-type structure is formed. The cell parameters decrease and the Curie temperature increases with increasing of the Co content. In the case of the Tb3(Fe1−xCox)27.4V1.6 series in the M(T) curve a magnetic transition is observed which is attributed to spin reorientation phenomena. This critical temperature decreases with increasing Co from 473 K for x=0.1 to 393 K for x=0.3, and was not observed in the case of 0.4. XRD patterns of magnetically aligned powder samples reveal the presence of a tilted magnetic structure.  相似文献   

11.
The electrical resistivity and the magnetization have been measured in the CsCl-type compounds, NixAl1?x, (Ni0.75Co0.25)0.52Al0.48 and Ni0.90Fe0.10)0.52Al0.48. A Kondo effect is observed due to substitutional Co and Fe atoms.  相似文献   

12.
The heat capacity of the Y3Ni13−xCoxB2 series has been measured from 300 mK to RT. The magnetic ordering phase transitions have been characterized as second-order type and the Tc's determined. The electronic contribution to the low-temperature heat capacity for x=0 yields an electronic constant γ=54 mJ mol K2, which is higher than those of YNi5 and YNi4B, proving experimentally that its density of states at the Fermi surface is larger than in those other compounds. The substitution of Ni by Co increases γ linearly. Electronic band calculations could explain these features.  相似文献   

13.
The onset of magnetism as a function of concentration and the magnetic properties of nine ternary Laves phase systems A(Fe1-xBx)2 (A=Y, Zr, U; B=Mn, Co and Al) are discussed in terms of homogeneous and heterogeneous models based on the SEW model and the Landau theory of phase transition of second order. A significant influence of the nomagnetic elements Y, Zr and U upon the Fe magnetic moment substituted by Mn, Co and Al is observed. Low temperature freezing phenomena affect the magnetization process around the critical concentration xc in Y and Zr compounds while they seem to be of minor importance for the U systems. Comparing the magnetic properties of these nine systems implies that the magnetization process becomes more homogeneous in the sequence of Y-, Zr- and U(Fe, B)2 compounds. This - together with volume considerations and the different magnetovolume effects observed as well as susceptibility measurements lead to the suggestion that the Fe moment tends to become more delocalized as one proceeds from Y to U compounds as a consequence of the growing extent to which Y, Zr, U d-electrons are hybridized with the 3d electrons. Furthermore, U can be regarded as tetravalent in these Laves phase compounds, except UAl2, in which presumably an admixture of U3+ and U4+ occurs.  相似文献   

14.
Cobalt iron cyanide with both Co and Fe in mixed valence states were prepared and characterized. In this mixed valence system the cobalt atom is found both as high spin Co(2+) and low spin Co(III) while iron always appears in low spin state to form two solid solutions: Co(2+)Co(III) hexacyanoferrates (II,III), and Co(2+)Co(III) hexacyanoferrate (II). Such solid solutions have the following formula units: (Co2+)x(CoIII)1−xK[(FeII)1−x(FeIII)x(CN)6]·H2O and (Co2+)1.5x(CoIII)1−xK[FeII(CN)6yH2O (0?x?1, 1?y?14). Compounds within these two series were characterized from Infrared, Mössbauer, X-ray diffraction and thermo-gravimetric data, and magnetic measurements at low temperature. A model for their crystal structure is proposed and the structure for a representative composition refined from XRD powder patterns using the Rietveld method. A simple and reproducible procedure to prepare these solid solutions is provided. Within hexacyanoferrates, such mixed valence states system in both metal centres shows unique features, which are discussed from the obtained data.  相似文献   

15.
Magnetic measurements have been performed on single crystals of Yni5 and GdNi5 and on polycrystalline samples of GdxY1?xNi5. YNi5 is a Pauli paramagnet, the susceptibility of which is enhanced by exchange and slightly temperature dependent (χ = 23 × 10?4 emu/mole at 4.2 K). In GdNi5, where the anisotropy is very weak, a polarization of the d band opposite to the Gd magnetization is observed. At 4.2 K, this polarization is 0.16 ± 0.02μB/Ni. The decrease of this polarisation with decreasing magnetic interactions has been studied in GdxY1?xNi5-type alloys. It is concluded that the polarization is more homogeneous than that of cobalt observed in GdxY1?xCo2.  相似文献   

16.
The nuclear magnetic resonance of59Co nuclei in magnetic domains of RCo3(R:Y, Nd, Sm, Gd, Tb, Dy and Ho) has been measured under external fields up to about 50 kOe at 4.2 K. To assign the observed NMR signals to each Co site, the59Co nuclear magnetic resonance of R(Co1−xNix)3 and R(Co1−xFex)3 has also been measured under the same conditions. The results of NMR studies show that the cobalt atoms at the 6c site in the light R compounds(YCo3, NdCo3 and SmCo3) and these at the 3b site in the heavy R compounds(GdCo3, TbCo3 and HoCo3) have a large orbital contribution.  相似文献   

17.
M-type hexaferrites with Co2+ and Ni2+ions substituting for Fe3+ ions (Ca0.30Sr0.35La0.35Fe12.0−x(Co0.5Ni0.5)xO19, 0.0 ≤ x ≤ 1.0) were prepared by the traditional solid state method. X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), physical property measurement system-vibrating sample magnetometer (PPMS-VSM) have been employed to study the microstructures and magnetic properties of hexaferrites. XRD patterns showed that the single magnetoplumbite phase is obtained if Co–Ni content (x) ≤ 0.4 and impurity phases are observed in the structure when Co–Ni content (x) ≥ 0.4. FE-SEM micrographs showed that the hexaferrites with hexagonal platelet-like grains is obtained. The saturation magnetization (Ms), remanent magnetization (Mr), Mr/Ms ratio, magneton number (nB), coercivity (Hc), magnetic anisotropy field (Ha) and first anisotropy constant (K1) decrease with increasing Co–Ni content (x) from 0.0 to 1.0. And our reported results with tunable Hc and Mr can be used for recording applications.  相似文献   

18.
Magnetic properties of the compounds Y15Fe77−xTxB8, where T stands for Mn, Co or Ni and x equals 7 or 17 were investigated within the temperature range 80 to 650 K. X-ray diffraction yielded a tetragonal structure of Nd2Fe14B type for all samples. The compounds appeared ferromagnetic: substitution of Mn or Ni for Fe leads to decrease of the Curie temperature and magnetization, while an increase of both quantities was observed for T = Co.  相似文献   

19.
Neutron diffraction studies of the nomagnetic compositional range of the Y6(Fe1?xMnx)23 system reveal the presence of preferential ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range of the ternary system, Mn atoms prefer to occupy the f2 site and Fe atoms the f1 site. Refinements of the data were carried out using the Rietveld profile method.  相似文献   

20.
The57Fe magnetic hyperfine fieldH hf at 77 K and 293 K and the lattice parametersc anda of the intermetallic compound Y (Fe1?x Co x )3 have been investigated as a function of the Co concentration for 0.0≤x≤0.99 by Mössbauer spectroscopy and X-ray diffraction, respectively. The magnetic hyperfine fieldH hf shows a Slater-pauling type concentration dependence with a maximum atx=0.4 and a strong decrease towards high Co concentrations.  相似文献   

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