Broadening and shift of thalliumnP 1/2,3/2 states (n=6–10) perturbed by noble gases

Impact broadening and shift of the transitions Tl 6P _1/2?nP _1/2,3/2 (n=7, 9, 10) and 6P _3/2?9P _{1/2, 3/2} are measured by high resolution Doppler-free two-photon spectroscopy. For excited states with small principal quantum numbers the results are in accord with values obtained fromC ₆-C ₈-C ₁₂ potentials calculated semiempirically. For intermediate principal quantum numbers the experiments show that the elastic scattering of the valence electron at the noble gas atom must be considered additionally. The experimental shift rates ofP _1/2 states are found to be larger than ofP _3/2 states. Furthermore, the line shifts of the one- and two-photon transitions concerning the 6P _1/2, 6P _3/2, 9P _1/2, 9P _3/2, 7S _1/2 states show that the contribution of the lower level of the transition must be considered too.     

Hyperfine structure measurements of103Rh

Hyperfine structure has been measured in 28 states of¹⁰³Rh below 34,000 cm^?1. The magnetic dipole interactionA constants in the metastable states 4d ⁸ 5s ⁴ P _5/2,3/2,² P _3/2,1/2,² D _5/2,3/2,² G _9/2,7/2 and 4d ⁷ 5s ^{2 4} F _{9/2,7/2,5/2,3/2} have been determined using the laser radio-frequency double-resonance method and in the states 4d ⁸ 5p ⁴ D _{7/2,5/2,3/2,1/2},⁴ G _7/2,5/2,⁴ F _{9/2,7/2,5/2,3/2},² G _9/2,7/2,² F _7/2,5/2 and² D _5/2,3/2 by high-resolution laser spectroscopy.     

Evaluating membrane cell e.m.f.ś from different schems of integration of the relevant nernstian equations

Computing the e.m.f. E (and the related membrane potential E_M) of the general concentration cell: electrode J ¦ IJ (m₁) in S ¦ membrane I ¦ IJ (m₂) in S ¦ electrode J (where the membrane perm-selective to counterion I separates two solutions of molalities m₁ and m₂ of the same electrolyte IJ, one mole of which forms n_I moles of I of valency z_I and n_J moles of coion J of valency z_J, with n=n_I+n_J) requires integration between limits m₁ and m₂ of the differential equation: dE=[nRT/Fn_J|z_J|] [τ_Iz_I, - mτ_sM_s]dln(mγ)_IJ, where the transference numbers τ_I of I and τ_s of the solvent S through the membrane are customarily taken as constant. The key point is the integration of the term mdln(mγ), which in the current practice is oversimplified to give [(m₁ + m₂)/2] in (m₂γ₂/m₁γ₁), and may cause large overestimation of the solvent-transfer contribution, with unreliable results for E and E_M. The procedure recommended here is instead that of splitting

mdln(mγ) into the “ideal part”

mdlnm=m₂-m₁ and the “non-ideal part”

mdlnγ, the latter being safely integrable putting lnγ as an explicit function of m in terms of the extended Debye-Hückel equation. Alternative and equally reliable procedures are described.     

Synthesis, crystal structures and ionic conductivities of Bi14P4O31 and Bi50V4O85. Two members of the series Bi18−4mM4mO27+4m (M=P, V) related to the fluorite-type structure

The two hitherto unknown compounds Bi₁₄P₄O₃₁ and Bi₅₀V₄O₈₅ were prepared by the direct solid-state reaction of Bi₂O₃ and (NH₄)H₂PO₄ or V₂O₅, respectively. Bi₁₄P₄O₃₁ crystallizes in a C-centred monoclinic symmetry (C2/c space group) with the unit-cell parameters: , , and β=93.63(1)° (Z=16). The symmetry of Bi₅₀V₄O₈₅ is also monoclinic (I2/m space group) with lattice parameters of , , and β=90.14(1)° (Z=2). Both structures correspond to a fluorite-type superstructure where the Bi and P or V atoms are ordered in the framework. An idealized structural model is proposed where the structures result of the stacking of mixed atomic layers of composition [Bi₁₄M₄O₃₁] and [Bi₁₈O₂₇] respectively. This new family can be formulated Bi_18−4mM_4mO_27+4m with M=P, V and where the parameter m (0?m?1) represents the ratio of the number of [Bi₁₄M₄O₃₁] layers to the total number of layers in the sequence. Bi₁₄P₄O₃₁ corresponds to m=1 when Bi₅₀V₈O₈₅ corresponds to m=1/3. In this last case, the structural sequence is simply one [Bi₁₄V₄O₃₁] layer to two [Bi₁₈O₂₇] layers. As predicted by the proposed structural building principle, Bi₁₄P₄O₃₁ is not a good ionic conductor. The conductivity at 650 °C is 4 orders of magnitude lower from those found in Bi₄₆M₈O₈₉ (M=P, V) (m=2/3) and Bi₅₀V₄O₈₅ (m=1/3).     

High Lithium Capacity MxV2O5Ay·nH2O for Rechargeable Batteries

The aqueous synthesis and electrochemical properties of nanocrystalline M_xV₂O₅A_y·nH₂O are described. It is easily and quickly prepared by precipitation from acidified vanadate solutions. M_xV₂O₅A_y·nH₂O has been characterized by X-ray powder diffraction, electron microscopy, TGA, chemical analyses, and electrochemical studies. The atomic structure is related to that of xerogel-derived V₂O₅·nH₂O. In M_xV₂O₅A_y·nH₂O, M is a cation from the starting vanadate salt and A is an anion from the mineral acid. This material exhibits high, reversible Li capacity and may be considered for use in a cathode in primary and secondary batteries. The lithium capacity of an electrode composed of M_xV₂O₅A_y·nH₂O/EPDM/carbon (88/4/8) is ∼380(mA h)/g (C/80 rate) and the energy density is ∼1000(W h)/kg (120-μm-thick cathode, 4-1.5 V, versus Li metal anode). Critical parameters identified in the synthesis of M_xV₂O₅A_y·nH₂O, with respect to achieving high Li-ion insertion capacity, are acid/vanadium ratio, starting vanadate salt, and temperature. Inclusion of carbon black in the synthesis yields a composite that maintains the high Li capacity, lowers the electrochemical-cell polarization, and preserves the lithium capacity at higher discharge rates. Li-ion coin cells, using pre-lithiated graphite anodes, exhibit electrochemical performance comparable to that of Li-metal coin cells.     

Syntheses and structures of three new scandium selenites: Sc2(SeO3)3·H2O, Sc2 (SeO3)3·3H2O and CsSc3(SeO3)4 (HSeO3)2·2H2O

Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc₂(SeO₃)₃·H₂O crystallizes as a new structure type containing novel ScO₇ pentagonal bipyramidal and ScO₆₊₁ capped octahedral coordination polyhedra. Sc₂(SeO₃)₃·3H₂O contains typical ScO₆ octahedra and is isostructural with its M₂(SeO₃)₃·3H₂O (M=Al, Cr, Fe, Ga) congeners. CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O contains near-regular ScO₆ octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected pyramidal [SeO₃]^2- selenite groups. Crystal data: Sc₂(SeO₃)₃·3H₂O, M_r=524.85, trigonal, R3c (No. 161), , , , Z=6, R(F)=0.018, wR(F²)=0.036; Sc₂(SeO₃)₃·H₂O, M_r=488.82, orthorhombic, P2₁2₁2₁ (No. 19), , , , , Z=4, R(F)=0.051, wR(F²)=0.086; CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O, M_r=1067.60, orthorhombic, Pnma (No. 62), , , , , Z=4, R(F)=0.035, wR(F²)=0.070.     

Ordered perovskites in the A(Li1/4Nb3/4)O3-A(Li2/5W3/5)O3 (A=Sr, Ca) systems

Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A²⁺(Li_1/4Nb_3/4)O₃-(x)A²⁺(Li_2/5W_3/5)O₃ systems, A²⁺=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P2₁/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b⁻b⁻c⁺ octahedral tilting. Rietveld refinements of the ordered A(B^I_1/3B^II_2/3)O₃ structures give a good fit to a model with B^I occupied by Li and Nb, B^II by W and Nb, and a general stoichiometry (Sr,Ca)(Li_3/4+y/2Nb_1/4−y/2)_1/3(Nb_1−yW_y)_2/3O₃, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites.     

Syntheses and structures of six compounds in the A2LiMS4 (A=K, Rb, Cs; M=V, Nb, Ta) family

Six new compounds in the A₂LiMS₄ (A=K, Rb, Cs; M=V, Nb, Ta) family, namely K₂LiVS₄, Rb₂LiVS₄, Cs₂LiVS₄, Rb₂LiNbS₄, Cs₂LiNbS₄, and Rb₂LiTaS₄, have been synthesized by the reactions of the elements in Li₂S/S/A₂S₃ (A=K, Rb, Cs) fluxes at 773 K. The A and M atoms play a role in the coordination environment of the Li atoms, leading to different crystal structures. Coordination numbers of Li atoms are five in K₂LiVS₄, four in A₂LiVS₄ (A=Rb, Cs) and Cs₂LiNbS₄, and both four and five in Rb₂LiMS₄ (M=Nb, Ta). The A₂LiVS₄ (A=Rb, Cs) structure comprises one-dimensional chains of tetrahedra. The Rb₂LiMS₄ (M=Nb, Ta) structure is composed of two-dimensional layers. The Cs₂LiNbS₄ structure contains one-dimensional chains that are related to the Rb₂LiMS₄ layers. The K₂LiVS₄ structure contains a different kind of layer.     

Long-range ordering in the Bi1−xAexFeO3−x/2 perovskites: Bi1/3Sr2/3FeO2.67 and Bi1/2Ca1/2FeO2.75

Two-ordered perovskites, Bi_1/3Sr_2/3FeO_2.67 and Bi_1/2Ca_1/2FeO_2.75, have been stabilized and characterized by transmission electron microscopy, Mössbauer spectroscopy and X-ray powder diffraction techniques. They both exhibit orthorhombic superstructures, one with a≈b≈2a_p and c≈3a_p (S.G.: Pb2n or Pbmn) for the Sr-based compound and one with a≈b≈2a_p and c≈8a_p (S.G.: B222, Bmm2, B2mm or Bmmm) for the Ca-based one. The high-resolution transmission electron microscopy (HRTEM) images evidence the existence of one deficient [FeO_x]_∞ layer, suggesting that Bi_1/3Sr_2/3FeO_2.67 and Bi_1/2Ca_1/2FeO_2.75 behave differently compared to their Ln-based homolog. The HAADF-STEM images allow to propose a model of cation ordering on the A sites of the perovskite. The Mössbauer analyses confirm the trivalent state of iron and its complex environment with three types of coordination. Both compounds exhibit a high value of resistivity and the inverse molar susceptibility versus temperature curves evidence a magnetic transition at about 730 K for the Bi_1/3Sr_2/3FeO_2.67 and a smooth reversible transition between 590 and 650 K for Bi_1/2Ca_1/2FeO_2.75.     

Mononuclear rhenium(III) and rhenium(II) complexes of 1,2-bis(diphenylphosphino)ethylene: The structure of trans-ReCl2(dppee)2

The mononuclear rhenium(III) complexes trans-[ReX₂(dppee)₂]X · nH₂O (X = Cl or Br, dppee = Ph₂PCHCHPPh₂) have been prepared by the reaction of (n-BU₄N)₂Re₂X₈ with dppee in methanol-conc. HX; in the case of X = Cl, ethanol may also be used as the reaction solvent. These salts undergo anion exchange reactions with ClO₄⁻ and/or PF₆⁻. The rhenium(II) complex trans-ReCl₂(dppee)₂ can be prepared by the cobaltocene reduction of trans-[ReCl₂(dppee)₂]Cl · 4H₂O and the reaction of Re₂Cl₆(PBu₃)ⁿ₂ with dppee in refluxing ethanol. The spectroscopic and electrochemical properties of [ReX₂(dppee)₂]⁺ have been investigated. Cyclic voltammetry (in 0.1 M tetra-n-butyl-ammonium hexafluorophosphate-CH₂Cl₂ with a Pt-bead electrode) shows reversible redox processes at E_1/2(ox) ca +1.5 V, E_1/2(red) ca −0.2 V, and E_1/2(red) ca −1.4 V vs Ag-AGCl that correspond to the Re(IV)-Re(III), Re(III)-Re(II) and Re(I)-Re(l) couples, respectively. The single-crystal X-ray crystal structure of trans-ReCl₂(dppee)₂ has confirmed its octahedral geometry. This complex crystallizes in the monoclinic space group P2₁/c with the following unit-cell dimensions: a = 11.321(2)Å, b = 13.011(2)Å, c = 17.242(3)Å, β = 95.79(2)°, V = 2527(1)ų, and Z = 2. The structure was refined to R = 0.041 (R_w = 0.070) for 2430 data with F² > 3.0σ(F²). The ReCl and ReP distances are 2.422(2) and 2.405(2)Å, respectively.     

Ground- and excited stateg-factors of Ba+

We observed the Zeeman-splitting of the 6S _1/2-6P _1/2 resonance transition of Ba⁺ ions (493.4 nm) in a 6 T magnetic field. The ions were stored in a Penning quadrupole trap. From the splitting and the simultaneously measured cyclotron frequency of stored electrons we derived theg-factors of the 6S _1/2 and 6P _1/2 states. The results areg(6S _1/2)=2.00267(20) andg(6P _1/2)=0.66634(22).     

REAuAl4Ge2 and REAuAl4(AuxGe1−x)2 (RE=rare earth element): Quaternary intermetallics grown in liquid aluminum

The two families of intermetallic phases REAuAl₄Ge₂ (1) (RE=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb) and REAuAl₄(Au_xGe_1−x)₂ (2) (x=0.4) (RE=Ce and Eu) were obtained by the reactive combination of RE, Au and Ge in liquid aluminum. The structure of (1) adopts the space group R-3m (CeAuAl₄Ge₂, , ; NdAuAl₄Ge₂, , ; GdAuAl₄Ge₂, , ; ErAuAl₄Ge₂, , ). The structure of (2) adopts the tetragonal space group P4/mmm with lattice parameters: , for EuAuAl₄(Au_xGe_1−x)₂ (x=0.4). Both structure types present slabs of “AuAl₄Ge₂” or “AuAl₄(Au_xGe_1−x)₂” stacking along the c-axis with layers of RE atoms in between. Magnetic susceptibility measurements indicate that the RE atoms (except for Ce and Eu) possess magnetic moments consistent with +3 species. The Ce atoms in CeAuAl₄Ge₂ and CeAuAl₄(Au_xGe_1−x)₂ (x=0.4) appear to be in a mixed +3/+4 valence state; DyAuAl₄Ge₂ undergoes an antiferromagnetic transition at 11 K and below this temperature exhibits metamagnetic behavior. The Eu atoms in EuAuAl₄(Au_xGe_1−x)₂ (x=0.4) appear to be in a 2+ oxidation state.     

Liquid-liquid phase equilibria for some polystyrene-methylcyclohexane mixtures

Liquid-liquid cloud point diagrams of solutions of nearly monodisperse samples of polystyrene (PS), and binary mixtures of nearly monodisperse PS’s, both in methylcyclohexane (MCH), were determined for several polymer molecular weights (M_w) at 0.1 MPa. The bimodal mixtures (PS[M_w(1),ρ(1)] + PS[M_w(2),ρ(2)], M_w(1)=90×10³ g/mol, M_w(2)=13×10³ g/mol, 5.78 × 10³ g/mol, and 2.2 × 10³ g/mol, ρ=1.06) were prepared constraining 〈M_w〉=38.6×10³ g/mol, ρ=M_w/M_n is the polydispersity index. In each case the cloud point curves (CPC’s) for the bimodal mixtures are strongly skewed, lying well above CPC for 〈M_w〉 when φ<φ_CRITICAL, and below CPC for 〈M_w〉 when φ>φ_CRITICAL; φ is volume fraction polymer in the polymer/solvent mixture. The experimental results are discussed in the context of empirical and mean-field representations.     

The structural and electric properties of the perovskite system BaTiO3–Ba(Fe1/2Ta1/2)O3

Compounds in the pseudo-binary BaTiO₃–Ba(Fe_1/2Ta_1/2)O₃ system have been synthesized at 1500°C in air and characterized by X-ray and electron diffraction as well as impedance analysis and Mössbauer spectroscopy. The symmetry of Ba(Fe_1/2Ta_1/2)O₃ is found to be trigonal with the space group P3m1. Two solid solutions exist in the BaTi_1−xFe_x/1Ta_x/1O₃ system at room temperature. The first (SS1) is in the composition range 0⩽x⩽0.07 and is tetragonal, P4mm, while the second broader solid solution, (SS2) 0.12⩽x⩽1, is trigonal and has the space group P3m1. The conductivity becomes higher with reduced amount of Ti in the structure. The activation energy of conductivity differs between the two solid solutions, 0.80 eV for SS1 and 0.30 eV for SS2, which indicates different mechanisms. The maximum of the real part of the permittivity recorded for compounds in SS1 decreases towards room temperature with increasing amount of Fe/Ta doping and a high dielectric constant of around 7000 is found for BaTi_0.94Fe_0.03Ta_0.03O₃.     

Structural analysis of several W(VI) and Mo(VI) complex perovskites prepared by the polymeric precursors method

We describe in this work the synthesis by the Pechini method of five Mo(VI)- and W(VI)-containing complex perovskites and their structural characterisation by HREM and XRD. The compounds studied, Ba(B_2/3′B_1/3″)O₃ (B′=In and Y; B″=W and Mo) and Sr(In_2/3W_1/3)O₃, were obtained after firing the precursor powders for 8 h at 1200°C. Thermal analysis showed that the formation mechanism of the five perovskites is similar and implies the formation of barium carbonate and barium tungstates or molybdates of different stoichiometries as intermediate phases. Interesting enough, these similar mechanisms yield to materials of a quite different structure. Indeed, Ba(In_2/3Mo_1/3)O₃ and Sr(In_2/3W_1/3)O₃ were found to be disordered perovskites (unit cells: a_p×a_p×a_p and , respectively); on the other hand, two phases coexist in the sample Ba(In_2/3W_1/3)O₃ at the synthesis conditions: an ordered predominant phase (unit cell: 2a_p×2a_p×2a_p) and, as a minor phase, a disordered perovskite (unit cell: a_p×a_p×a_p). Finally, the two yttrium-containing compounds were found to be ordered perovskites (2a_p×2a_p×2a_p).     

Structure and Jahn-Teller effect in mixed crystals Rb2Cr1−xMnxCl4: A single-crystal neutron diffraction study and spectroscopic results

The structures of single crystals Rb₂Cr_1?xMn_xCl₄ (0 ? x ? 1) have been studied by neutron diffraction. A crystal of composition x = 0.01 shows a superstructure of the K₂NiF₄ type [space group Bbcm; a = b = 7.262Å, c = 15.733Å]. The structural refinement [R = 0.043] yields an antiferrodistortive order of tetragonally elongated octahedra (superimposed by a small orthorhombic component) with CrCl bond lengths of 2.43 Å (∥[001]) and 2.40 Å, 2.74 Å (⊥[001]). Structural results for x = 0.01/0.08/0.53/0.63/0.83/0.91/0.97 in space group $\text{I4}\text{mmm}$ [K₂NiF₄ type]—in particular the anomalous ms displacements of Cl(1) in the (001) plane—give evidence that the distortion of the (Mn, Cr)Cl₆ octahedra decreases with increasing x. AOM calculations based on experimental ligand field energies indicate that the individual CrCl₆ polyhedra are more strongly distorted than the (Jahn-Teller stable) MnCl₆ octahedra in mixed crystals with larger x values.     

Synthesis, crystal structure and characterization of new 12H hexagonal perovskite-related oxides Ba6M2Na2X2O17 (M=Ru, Nb, Ta, Sb; X=V, Cr, Mn, P, As)

The new Ba₆Ru₂Na₂X₂O₁₇ (X=V, Mn) compounds have been prepared by electrosynthesis in molten NaOH and their crystal structures have been refined from single crystals X-ray diffraction, space group P6₃/mmc, Z=2, for X=V: , , R₁=4.76%, for X=Mn : , , R₁=3.48%. The crystal structure is a 12H-type perovskite with a (c′cchcc)₂ stacking sequence of [BaO₃]_c, [BaO₃]_h and [BaO₂]_c′ layers. The tridimensional edifice is formed by blocks of Ru₂O₉ dimers that share corners with NaO₆ octahedra. These blocks sandwich double sheets of X⁵⁺O₄ tetrahedra. Several isotypic Ba₆M⁵⁺₂Na₂X⁵⁺₂O₁₇ materials (X=V, Cr, Mn, P, As) and (M=Ru, Nb, Ta, Sb) have been prepared by solid state reaction and characterized by Rietveld analysis. The magnetic and electric properties have been investigated and show besides the Ru⁵⁺₂O₉ typical intradimer antiferromagnetic couplings, discrepancies of both χ and ρ versus T at 50 and 100 K for Ba₆Ru₂Na₂X₂O₁₇ (X=V, As). In this work, a review of the identified Ru-hexagonal perovskite materials is also reported in order to overview the wide variety of possibilities in the field of new compounds synthesis.     

La(Li1/3Ti2/3)O3: a new 1:2 ordered perovskite

A new 1:2 ordered perovskite La(Li_1/3Ti_2/3)O₃ has been synthesized via solid-state techniques. At temperature >1185°C, Li and Ti are randomly distributed on the B-sites and the X-ray powder patterns can be indexed in a tilted (b⁻b⁻c⁺) Pbnm orthorhombic cell (a=a_c√2=5.545 Å, b=a_c√2=5.561 Å, c=2a_c=7.835 Å). However, for T?1175°C, a 1:2 layered ordering of Li and Ti along 〈111〉_c yields a structure with a P2₁/c monoclinic cell with a=a_c√6=9.604 Å, b=a_c√2=5.552 Å, c=a_c3√2=16.661 Å, β=125.12°. While this type of order is well known in the A²⁺(B²⁺_1/3B⁵⁺_2/3)O₃ family of niobates and tantalates, La(Li_1/3Ti_2/3)O₃ is the first example of a titanate perovskite with a 1:2 ordering of cations on the B-sites.     

A phase-analytical study of the TlCuSe system

High-temperature silica-tube syntheses and room-temperature copper extraction experiments of the single phases found with the former technique have established five new ternary phases in the TlCuSe system. The compositions were determined by microprobe analysis. The new phases have been crystallographically characterized by means of single-crystal and powder diffraction: TlCu₃Se₂ (CsAg₃S₂ type),a = 15.2128(7)Å,b = 4.0115(2)Å,c = 8.3944(4)Å, β = 111.700°(4); Tl₅Cu₁₄Se₁₀ (new type),C2/m?)a = 18.097(2)Å,b = 3.9582(2)Å,c = 18.118(2)Å, β = 116.089°(7); TlCu₅Se₃ (new type,P4¯n2?),a = 12.9023(2)Å,c = 3.9905(1)Å; TlCu_5−xSe₃ (new type,Pnn2?),a = 12.43(1)Å,b = 12.80(1)Å,c = 3.93(1)Å; TlCu₇Se₄ (NH₄Cu₇S₄ type),a = 10.4524(2)Å,c = 3.9736(1)Å. The latter phase may be considered as stoichiometric crookesite.     

Magnetic structure of rare-earth dodecaborides

We have investigated the magnetic structure of HoB₁₂, ErB₁₂ and TmB₁₂ by neutron diffraction on isotopically enriched single-crystalline samples. Results in zero field as well as in magnetic field up to 5 T reveal modulated incommensurate magnetic structures in these compounds. The basic reflections can be indexed with q=(1/2±δ, 1/2±δ, 1/2±δ), where δ=0.035 both for HoB₁₂ and TmB₁₂ and with q=(3/2±δ, 1/2±δ, 1/2±δ), where δ=0.035, for ErB₁₂. In an applied magnetic field, new phases are observed. The complex magnetic structure of these materials seems to result from the interplay between the RKKY and dipole-dipole interaction. The role of frustration due to the fcc symmetry of dodecaborides and the crystalline electric field effect is also considered.