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1.
Magnetic anisotropy of Fe/RE multilayers (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) was studied using 57Fe Mössbauer spectroscopy. Perpendicular magnetic anisotropy was observed in Fe/Pr, Fe/Nd, Fe/Tb, and Fe/Dy multilayers. The external field dependence of the direction of magnetic moments was also examined for Fe/Tb multilayers. The results imply that the perpendicular magnetic anisotropy originates from the single ionic anisotropy of RE at the interfaces.  相似文献   

2.
A study of theEXAFS associated with theK x-ray absorption discontinuity of germanium in pure germanium and in the rare-earth germanides RGe2 (where R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been carried out. The Ge-Ge distances have been obtained in these compounds. Considering the phase to the RGe2 system, the bond lengths in these compounds have been determined. The values obtained by us for the RGe2 compounds (R=La, Ce, Pr, Nd, Sm, Gd, Dy and Y) agree with those obtained earlier by crystallographic methods. The bond lengths for the compounds TbGe2, HoGe2 and ErGe2 are also being reported.  相似文献   

3.
DC magnetic susceptibility and resistivity measurements have been performed on 14 Tl(Sr1.5R0.5)CaCu2O7−δ compounds with R=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. All samples except the Ce-doped compound show superconducting phase transition temperature around 80–90 K. The rare-earth atoms behave as local moments above the superconducting transition temperature of these compounds. Mechanism of filling of holes in the CuO2 plane can be employed to interpret the suppression or enhancement of superconductivity by rare-earth ions in Tl(Sr1.5R0.5)CaCu2O7−δ.  相似文献   

4.
The magnetic properties of RNi4Ga (R=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm and Lu) compounds have been investigated. These compounds form in a hexagonal CaCu5 type structure with a space group P6/mmm. Compounds with the magnetic rare earths, R= Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm, undergo a ferromagnetic transition at 5, 17, 20, 19, 12, 3.5, 8 and 6.5 K, respectively. The transition temperatures are smaller compared to their respective parent compounds RNi5. PrNi4Ga is paramagnetic down to 2 K. LaNi4Ga and LuNi4Ga are Pauli paramagnets. All the compounds show thermomagnetic irreversibility in the magnetically ordered state except GdNi4Ga.  相似文献   

5.
Four new ternary boride systems with the CeCo3B2-type structure are reported with the general formulae: MRu3B2 (M = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Th or U), MRh3B2 (M = La, Ce, Pr, Nd, Sm, Eu or Gd), MOs3B2 (M = Lu or U) and MIr3B2 (M = La, Th or U). Most members of these systems were found to become either superconducting or magnetically ordered. The structure and properties of these materials are discussed in relation to those of other ternary systems previously reported to exhibit superconductivity and/or magnetic order.  相似文献   

6.
Samples whose dominant phase is R5Fe18B18 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Lu) were prepared by arc melting and vacuum annealing.Low temperature differential susceptibility measurements on Nd5Fe18B18 indicate a ferromagnetic transition at T ≈ 14K and perhaps a second magnetic transition at T ≈ 7K whose nature is not yet clear. Magnetic transitions were also observed in materials with R = Pr, Sm, Gd, Dy, Ho.Room temperature 57Fe Mössbauer measurements showed all samples to be paramagnetic; the quadrupole splitting and isomer shift were determined. Low temperature Mössbauer measurements indicate no magnetic ordering of Fe down to 1.5 K.  相似文献   

7.
Ternary tetragonal compounds of the composition R2Fe14B were observed for R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The lattice constants and the X-ray density of these compounds were determined. Also determined were the magnetic properties, comprising the temperature dependence of the magnetization in the range 4.2–700 K and the field dependence of the magnetization at 4.2 K in fields up to 20 T. These latter measurements were made in two mutually perpendicular directions, making it possible to determine the anisotropy fields. The magnetocrystalline anisotropy was found to consist of contributions due to the Fe and rare-earth sublattice, respectively.  相似文献   

8.
The extended x-ray absorption fine structure (EXAFS) associated with the GeK x-ray absorption discontinuity in pure germanium and in the intermetallics RGe2 (R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been studied. The Ge-R distances in these compounds have been determined by comparing the experimental phase shifts with the theoretical ones. The Ge-R distances in the compounds TbGe2, HoGe2 and ErGe2 are being reported for the first time in this work.  相似文献   

9.
Among amorphous Fe2RE (RE=Er, Ce, Gd, La, Pr, Sm, Dy, Ho) alloys, Fe2Ce exhibits a tendency toward short range order, while the other Fe2RE compounds show clustering. However, we have almost no information about environments around Fe atoms. Using Mössbauer spectroscopy we have determined the quadrupole splitting distributionsP(QS) of two representative amorphous Fe2RE (RE=Ce, Er) alloys, leading to local environments of Fe atoms. The analysis of the mixed magnetic dipole and quadrupole interactions in Fe2Er shows two kinds of electrical field gradients (EFT) with the positive and negative signs in the sample, indicating a random packing of Fe atoms. Furthermore, the analyzed quadrupole splitting distributionP(QS) of Fe2Er also supports random packing in this amorphous alloy. On the other hand, the amorphous Fe2Ce alloy shows two kinds of distributions of quadrupole splitting; the major component indicating random packing and the minor component Ce-rich Ce-Fe clusters.  相似文献   

10.
The formation of the 1/1 crystal approximant phase (1/1 phase) to the icosahedral phase (i phase) in In-Pd-RE (RE: rare earth metal) systems has been investigated. A new series of 1/1 phases were found in In53Pd33RE14 (RE; Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) alloys. For Y, Sm, Gd, Tb, Dy, and Ho, the 1/1 phases were found in annealed alloys, indicating that they are thermodynamically stable. The atomic structure of the 1/1 phases was directly observed by high-angle annular dark-field imaging performed via scanning transmission electron microscopy, revealing that the 1/1 phases consisted of a periodic arrangement of Tsai-type icosahedral clusters. Further, the atomic size effect on i phase formation, as well as formation conditions previously reported for other Tsai-type i and 1/1 phases were examined. It was found that the ratio of the atomic radius of base metals such as In and Pd affects i phase formation. Moreover, the appropriate range of the radius ratio for i phase formation was narrower than that for 1/1 phase formation.  相似文献   

11.
New ternary silicides (RE,Th,U) Os2Si2 have been synthesized from the elements. All the compounds (RE= Y,La,Ce,Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb, Lu) were found to be isotypic and to crystallize with the ordered BaAl4-type of structure (ThCr2Si2-type). Magnetic properties of these alloys — studied in the temperature range 1.5<T<1100 K — reveal a typical Van Vleck paramagnetism of free RE3+ ions at temperatures higher than 300 K. The observed effective paramagnetic moment of CeOs2Si2, μ(eff)=0.98 BM, is compatible with a rather low concentration (15%) of Ce3+. The effective moment of SmOs2Si2, μ(eff)=0.47 BM, is in reasonable agreement with a Hund's rule J=52 ground level for free Sm3+. For temperatures above 25 K, the magnetic susceptibility as a function of temperature corresponds to the Van Vleck behavior for free Sm3+ (closely spaced multiplet, J=52,J=72. Magnetic ordering temperatures of REOs2Si2 silicides are generally below 42 K. (Pr,Nd,Ho,Er,Tm) Os2Si2 exhibit ferromagnetic ordering whereas (Sm,Gd, Tb,Dy) Os2Si2 show antiferromagnetic behavior. Above 1.8 K none of the samples was found to be superconducting.  相似文献   

12.
Ternary silicides (RE, Th, U)Ru2Si2 have been synthesized from the elements. All the compounds (RE = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were found to be isotypic and to crystallize with the structure type of ThCr2Si2 (ordered derivative of the BaAl4-type). The magnetic behavior of these alloys was studied in the temperature range 1.5 K < T < 1100 K. Magnetic susceptibilities at temperatures T > 300 K closely follow a typical Van Vleck paramagnetism of free RE3+-ions. In the case of CeRu2Si2 susceptibilities are well described for 20 K < T < 1100 K by a Van Vleck paramagnetism of widely spaced multiplets; the observed effective paramagnetic moment μeff = 2.12 BM indicates a high percentage (85%) of Ce3+. SmRu2Si2 yields an effective moment μeff = 0.54 BM, which compares reasonably well with the Hund's rule J = 5/2 ground level for free Sm+ and a low-lying excited level with J = 7/2. For temperatures T > 15 K the magnetic susceptibility as a function of temperature follows the “Van Vleck behavior” for free Sm3+. At low temperatures ferromagnetic ordering was encountered for (Pr, Nd, Ho, Er, Tm)Ru2Si2, whereas antiferromagnetic ordering was observed for (Sm, Gd, Tb, Dy)Ru2Si2. The ordering temperatures are generally below 55 K. No superconductivity was found for temperatures as low as 1.8 K.  相似文献   

13.
New ternary silicides of composition RCoSi2 (R=rare earth and Y) have been prepared and found to crystallize in the orthorhombic CeNiSi2-type structure. Their magnetic properties have been studied by means of susceptibility measurements between 2 and 250 K. The Ce and Y compounds show essentially temperature independent Pauli paramagnetism. The compounds with R=Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm show antiferromagnetic ordering below 20 K. The effective rare earh moments in the paramagnetic state agree well with the free ion values, and, for the heavy rare earths, the Néel temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Co sublattice.  相似文献   

14.
The crystal structure and magnetic properties of quaternary rare-earth intermetallic borides R3Co29Si4B10 with R=La, Ce, Pr, Nd, Sm, Gd and Dy have been studied by X-ray powder diffraction and magnetization measurements. All compounds crystallize in a tetragonal crystal structure with the space group P4/nmm. Compounds with R=La, Ce, Pr, Nd and Sm are ferromagnets, while ferrimagnetic behavior is observed for R=Gd and Dy. The Curie temperatures vary between 149 K and 210 K. The Curie temperatures in R3Co29Si4B10 (R=Ce, Pr, Nd, Sm, Gd, Dy) compounds are roughly proportional to the de Gennes factors.  相似文献   

15.
稀土五磷酸盐(REP5O14)晶体的光谱性质   总被引:4,自引:3,他引:1  
本文在较前人宽的波段内系统地研究了REP5O14(RE=Ce3+,Pr3+,Nd3+,Sm3+,Eu3+,Gd3+,Tb3+,Dy3+,Ho3+,Er3+,Tm3+,Yb3+)单晶的吸收光谱、激发光谱与荧光光谱.合理地确定了谱项.关于SmP5O14,GdP5O14,DyP5O14,TmP5O14与YbP5O14等晶体光谱的研究,至今尚未见报导.这些晶体系统的光谱数据,对于了解它们的性质及其应用方面,都是很有用的.  相似文献   

16.
We present the electrical resistivity measurements of equiatomic RPt compounds, with R  La, Pr, Nd, Gd, Tb, Dy, Ho and Er, which crystallize into two different orthorhombic structures. The different contributions to the total resistivity were separated. From the phonon contribution ϱp we estimated the Debye temperature θD of the different compounds. Except for GdPt, the increase of the magnetic resistivity above Tc arise from crystal field effects which are larger than those calculated in the point charge model. The paramagnetic Curie temperature and the saturated magnetic resistivity follow approximately the de Gennes law and allowed us to estimate effective mass and the exchange constant through the series.  相似文献   

17.
A systematic study has been made on formation condition, crystallographic structure and magnetic properties of RMo1.5Fe10.5Nx, where R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er. The interstitial nitrogen atom effects on Curie temperature, saturation magnetization and magneto-crystalline anisotropy have been investigated. Two important preliminary results have been obtained. (1) A single phase crystallized in the ThMn12-type structure was stabilized with a smaller content of molybdenum, thus, the compounds possess a higher Curie temperature and a larger spontaneous magnetization. (2) A complete system of compounds with 1:12 type structure containing the light rare earth cerium and praseodymium was synthesized, which will be favorable for developing new rare earth hard magnetic materials.  相似文献   

18.
The magnetic properties have been studied for the series of RNi5−xCux intermetallics with R=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu; x  ?2.5. Compositional dependences of magnetic susceptibility for the Pauli paramagnets (R=Y, La, Ce, Lu) and the Curie temperature for ferromagnets (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm) have maximum at x=0.2–0.4x=0.20.4 and 1, respectively. The substitution of Cu for Ni is accompanied by decreasing spontaneous magnetic moment and increasing coercive force of all ferromagnetic RNi5−xCux but GdNi5−xCux. These results are explained in the frame of band magnetism, random local crystal field, and domain wall pinning theories.  相似文献   

19.
Perturbed angular correlation spectroscopy has been used to investigate the combined magnetic and electric hyperfine interaction of the probe nucleus 111Cd in ferromagnetically ordered rare earth (R)-dialuminides RAl2 as a function of temperature for the rare earth constituents R=Pr, Nd, Sm, Eu, Tb, Dy, Ho and Er. In compounds with two magnetically non-equivalent Al sites (R=Sm, Tb, Ho, Er), the magnetic hyperfine field was found to be strongly anisotropic. This anisotropy is much greater than the anisotropic dipolar fields, suggesting a contribution of the anisotropic 4f-electron density to magnetic hyperfine field at the closed-shell probe nucleus. The spin dependence of the magnetic hyperfine field reflects a decrease of the effective exchange parameter of the indirect coupling with increasing R atomic number. For the compounds with the R constituents R=Pr, Nd, Tb, Dy and Ho the parameters B4, B6 of the interaction of the crystal field interaction have been determined from the temperature dependence of the magnetic hyperfine field. The 111Cd PAC spectrum of EuAl2 at 9 K confirms the antiferromagnetic structure of this compound.  相似文献   

20.
We report an extensive study of the magnetic properties of tetragonal RNi2Si2 compounds (R=Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm), through resistivity, neutron diffraction, susceptibility and magnetization experiments. All compounds exhibit complex incommensurate antiferromagnetic structures, while a transition occurs in TbNi2Si2 between a modulated phase and a simple antiferromagnetic structure, stable at low temperature. The magnitude of the bilinear exchange interactions deviates from the Gennes law and the direction of the ordered magnetic moments presents anomalies across the series, including the probable existence of other types of interactions between the rare earth ions.  相似文献   

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