Structural,electrical, and magnetic properties of R-Fe-Ge (R = Y,La, Sc) films

The structural, electrical, and magnetic properties of thin R-Fe-Ge (R = Y, La, Sc) films have been studied in relation to preparation conditions (annealing temperature and the action of an external electric field on molecular vapor), film thickness, and the size of the crystallites formed in the amorphous matrix. The resistivity and coercivity of the films have been measured at temperatures from 77 to 500 K,. The results are of practical interest because the films are potentially attractive as soft-magnetic nanocrystalline materials.     

NMR study of quaternary superconductor RM2B2C (R = Y,La, Th,and M = Ni,Pd, Pt)

¹⁹⁵Pt-,¹³⁹La- and¹¹B-NMR have been investigated in quaternary RM₂B₂C (R=Y, La, Th and M=Ni, Pd, Pt). The electric quadrupole frequency of¹³⁹La changes more than 5 times in magnitude from M=Ni to Pt, indicating that the hybridization of La-5d and d-electrons of M-element changes largely. The analysis of¹¹B and¹³⁹La spectra shows also the large change of the magnetic anisotropy with R and M element, i.e., _{II c}>_{II ab} in LaNi₂B₂C, but _{II c}>_{II ab} YNi₂B₂C.The data of T₁T and K of¹⁹⁵Pt and¹¹B are consistent with the band effects and with no evidence of strong antiferromagnetic correlation effects.     

Structural,magnetic and electronic transport studies of RAgSn2 compounds (R = Y,Tb, Dy,Ho and Er) with Cu3Au-type

RAgSn₂ compounds, where R = Y, Tb, Dy, Ho and Er, were synthesized by arc-melting and subsequent annealing at 870 K. The formation of cubic phases with Cu₃Au-type structure (space group ${\textit{Pm}}{\overline{3}}{\textit{m}}$ ) was studied. Magnetic property measurements showed that in paramagnetic state, the compounds with magnetic rare-earth atoms are Curie–Weiss paramagnets and order antiferromagnetically at low temperatures. YAgSn₂ is a Pauli paramagnet in 100–300 K temperature range. The electrical properties of RAgSn₂ compounds were investigated by means of electrical resistivity and Seebeck coefficient measurements in 4·2–300 K temperature range. All investigated compounds exhibit metallic type of conductivity. Electronic structure calculations based on full potential linearized augmented plane wave (FLAPW) method is also carried out to probe the magnetic and electronic structures of RAgSn₂ compounds. Comparisons between experimental data and calculations are discussed.     

Average Co magnetic moment of R-Co-B (R = Y,Pr and Nd) compounds

We estimate the average Co magnetic moment and account for the moment variation by a model in Y_{n + 1}Co_{3n + 5}B_2n (n = 0, 1, 2, 3 and ∞), Pr_{m + n}Co_{5m + 3n}B_2n (m = 2, n = 1 and m = 2, n = 3), Nd_{m + n}Co_{5m + 3n}B_2n (m = 3, n = 2) and Y₂Co₁₄B compounds. And we obtain the magnetic properties of hypothetical Y_{m + n}Co_{5m + 3n}B_2n (n = 1, m = 2, 3, 4 and 5) compounds.     

Properties of RBaCuFeO5+δ (R = Y, La, Pr, Nd, Sm-Lu)

The structural properties, thermal stability, thermal expansion, and electrical properties of the RBaCuFeO_5+δ (R = Y, La, Pr, Nd, Sm-Lu) layered ferrocuprates have been studied systematically. The linear thermal expansion coefficients of the RBaCuFeO_5+δ phases are ? 13 × 10^?6 and ? 13 × 10^?6 K^?1 for R = La-Eu and R = Gd-Lu, respectively. Their electrical conductivity varies widely, from σ = 2.0 × 10¹ S/cm for LaBaCuFeO_5.47 to σ = 8.4 × 10^?8 S/cm for TmBaCuFeO_5.06 at 300 K. The lattice parameters, thermal expansion, and conductivity of RBaCuFeO_5+δ vary nonmonotonically with the ionic radius of R³⁺ (atomic number of the rare earth), which is due to the fact that the 4f electrons of the rare-earth ions play a significant role in determining the structural and transport properties of these phases.     

Nonlinear Optical Properties of Ba3R(BO3)3(R = Y, Ho–Lu) Polar Crystals

Ba₃R(BO₃)₃(R = Y, Ho–Lu) crystals were prepared by a flux growth process, and there nonlinear optical properties were characterized by second harmonic generation measurements. The optical nonlinearity of the crystals was found to increase as the ionic radius of the rare-earth cation decreases.     

A DTA study of zone-refined LiRF4 (R=Y,Er)

The melting behaviour of zone-refined bars of LiYF₄ and LiErF₄ has been investigated by means of differential thermal analysis (DTA). Both compounds can be produced congruently under an atmosphere of carefully purified argon. Consideration of the constitutional variations occurring along the length of the bars has established that the congruent melting composition is non-stoichiometric, and a detailed analysis of the profiles of the thermal events indicates that both compounds possess a homogeneity range and are not line compounds as previously reported. The influence of purity on the melting behaviour is assessed and the implication of the results on the crystal growth of laser materials based on these compounds is discussed.     

Imperfections and impurity phases in flux grown RCrO3 (R = La,Yb) single crystals

Results of scanning electron microscopy (SEM) and energy dispersive X-ray analytical (EDAX) investigations, conducted on some elevated structures displayed by flux grown rare earth orthochromite, RCrO₃ (R = La, Yb) crystals, are presented. The peculiar structures exhibited by crystal surfaces indicate imperfections and impurity phases. EDAX of elevated structures reveals the various phases to be composed of lead associated materials which may probably be either Pb₂CrO₅ or Pb₂OF₂ (flux). Other secondary crystallization of impurity phases, ROF (R = La, Yb) is illustrated in the case of RCrO₃ (R = La, Yb) crystals. The elevated structures illustrate their non-stoichiometric behaviour. Precipitation of impurity phases and formation of imperfections during the growth of RCrO₃ (R = La, Yb) crystals and their effect on the crystalline quality is discussed.     

La2/3Sr1/3MnO3掺杂RE(RE=Pr、Eu、Y、Tb)的结构、红外及磁学性质

采用空气中固相反应烧结法制备了一系列钙钛矿结构的(La1-xREx)2/3Sr1/3MnO3(RE=Pr、Eu、Y、Tb;x=0、0.3或0.4)掺杂稀土锰氧化物多晶样品.X射线衍射(XRD)分析表明随着RE离子半径的减小,样品XRD的衍射峰位置普遍向高角度偏移,2θ增大0.02～0.62°.扫描电镜(SEM)观测的结果表明掺杂RE离子的半径越小,形成多晶样品的晶粒越小,未掺杂RE的La2/3Sr1/3MnO3在所有的样品中晶粒最大.红外吸收光谱测量发现样品在599～629cm-1范围出现了吸收峰并且峰的位置随掺杂RE离子半径的减小而向低频方向偏移.样品的磁性质测量表明掺杂稀土离子的半径及磁矩对材料的磁电阻有明显影响.     

Normal-state properties of RNi2B2C (R=Y,Ho,La) and anisotropic resistivity of single-crystal RNi2B2C (R=Lu,Er, Ho)

Normal-state measurements of RNi₂B₂C are reportedThe resistivity of polycrystalline RNi₂B₂C (R=Y, Ho and La) has been measured to 600K. All three compounds have a linear resistivity above 300K but the superconducting compounds show a distinct curvature below this temperature. The thermopower and static magnetic susceptibility have been measured for the same samples to 300–400K.Single crystals of the superconducting compounds RNi₂B₂C (R=Lu, Er, Ho) have been polished into geometric bars for direct measurement of the in-plane resistivity (p_a) and the c-axis resistivity (p_c). The in-plane resistivity of all three compounds is parallel and the effect of spin-disorder scattering is discussed. The resistivity shows very little anisotropy despite the layered structure of these materials.     

Interactions between nickel and melted R-Ba-Cu-O (R=Y,Nd)

R-Ba-Cu-O (R = Y and Nd) compounds were melted and crystallized in nickel crucibles. The interaction between these materials was studied by examining the physical aspect of the nickel interface. Interaction mechanisms between nickel and melted R-Ba-Cu-O compounds are proposed to explain the formation of an interface, constituted of a top layer of Ni_0.8Cu_0.2O_x and of an NiO_x underlayer as well as the presence of nickel oxide-rich particles in the melt.     

Growth of MBO3 (M = La, Y, Sc) and LaSc3(BO3)4 crystals from LiBO2-LiF fluxes

The solubility of rare-earth orthoborates and LaSc₃(BO₃)₄ in LiBO₂-LiF solvents has been studied. Spontaneous crystals have been grown and the solvent used has been shown to be attractive for the growth of bulk crystals at t ≤ 1000°C. The α- and γ-phases of LaSc₃(BO₃)₄ have been shown to be identical.     

Magnetic properties of RRh3B2(R=La,Ce, Nd,Gd) compounds

The¹¹Bnmr results on RRh₃B₂(R=La, Ce, Nd and Gd) are reported. For CeRh₃B₂, specific heat and electrical resistivity are reported. From a comparative study of the¹¹Bnmr Knight shifts and the spin lattice relaxation times of these compounds it is shown that in CeRh₃B₂, there is strong hybridization of 4f states with the conduction electrons. A local moment on Ce with admixture of 4f and 5d–6s orbitals is suggested.     

Ca_4RO(BO_3)_3(R=Gd,Y)晶体空间方向的确定

介绍了高质量Ｃａ4ＧｄＯ（ＢＯ3）3（ＧｄＣＯＢ）、Ｃａ4ＹＯ（ＢＯ3）3（ＹＣＯＢ）晶体的生长，报道了两种晶体空间方向的确定方法；对于该类低对称性非线性光学晶体的实用化具有推动意义．     

Antiferromagnetic interactions and Mössbauer study of LnMCuFeOδ Phases (Ln = Y,La; M = Ca,Sr, Ba)

A three-dimensional antiferromagnetic ordering 3D-AF atT _N ≈12K has been observed in these nonsuperconducting phases. In the compounds where a partial trivalent-divalent cationic substitution (Y by Ca or La by Sr) has been performed, this antiferromagnetic ordering is not observed above 4 K. Mössbauer spectroscopy studies indicate a unique iron environment and magnetic ordering; the spectra are consistent with the classic high spin Fe³⁺ although in an unusual fivefold coordination. Both the herein described transition and the formerly reported one at ～460 K are affected upon doping.     

助熔剂法合成RPO4（R=La,Ce,Tb）晶体的研究

本文研究了以(NH_4)_2HPO_4-Li_2CO_3-MoO_3(PbF_2)为助熔剂合成 RPO_4(R=La~(3 ),Ce~(3 ),Tb~(3 ))晶体的工艺,测试和分析了晶胞参数和晶体结构。对 CePO_4和 TbPO_4晶体的激发光谱和荧光光谱进行了讨论和分析。     

Hydrogenation and Anisotropic Expansions in R3Fe29-xTx (R = Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

1.IntroductionIntensiveinvestigatiOnsontheR-Fe-T(R=rareearth,T=transitionmetalasastabilizingelement)phasediagrams,locatedattheironrichcorner,ledtothediscoveryofthenovelR2(Fe,T)l9phase[1l2]duetothegreatinterestinhighperfOrmanceper-manentmagneticmaterials.ItsrealstoichiometriccompOsitionandcrystallographicstructurewerede-terminedasaNd3(Fe,Ti)29-typestructurewithmon-oclinicsymmetry[3]andtheA2/mspacegrOup[4]byX-rnypowderdiffractiOn(XRD)andthenthiswasconfirmedbyneutrOnpOwderdiffraction[5'6…     

Luminescence of the Bi3+ ion in compounds LnOCl (Ln = La,Y, Gd)

The luminescence spectra of LnOCl-Bi³⁺ (Ln = La, Y, Gd) are reported. In these compounds two luminescent centers are observed.In LaOCl-Bi³⁺ the luminescence is ascribed to isolated Bi³⁺ ions and to a second, BiOCl-rich, phase. In YOCl-Bi³⁺ and GdOCl-Bi³⁺ the luminescence is ascribed to Bi³⁺ pairs and also to a second, BiOCl-rich, phase. In GdOCl-Bi³⁺ energy transfer from Bi³⁺ to Gd³⁺ is observed.