Electric-field-gradient tensor and boron site-resolvedB11NMR in single-crystallineYB12 (original) (raw)
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XMCD Characterization of the Ferromagnetic State of Yb14MnSb11
Journal of the American Chemical Society, 2002
X-ray magnetic circular dichroism (XMCD) measurements on Yb14MnSb11 provide experimental evidence of a moment of 5 µB on Mn, with partial cancellation by an opposing moment on the Sb4 cage surrounding each Mn ion. The compound is isostructural to Ca14AlSb11, with Mn occupying the Al site in the AlSb4 9-discrete tetrahedral, anionic unit. Bulk magnetization measurements indicate a saturation moment of 3.90 (0.02 µB/formula unit consistent with four unpaired spins and implying a Mn 3+ , high-spin d 4 state. XMCD measurements reveal that there is strong dichroism in the Mn L23 edge, the Sb M45 edge shows a weak dichroism indicating antialignment to the Mn, and the Yb N45 edge shows no dichroism. Comparisons of the Mn spectra with theoretical models for Mn 2+ show excellent agreement. The bulk magnetization can be understood as Mn with a moment of 5 µB anda2 +configuration, with cancellation of one spin by an antialigned moment from the Sb 5p band of the Sb4 cage surrounding the Mn.
Yb2BaCoO5 magnetic and crystal structure determination from neutron scattering
Journal of Alloys and Compounds, 1998
The magnetic and crystal structure of Yb BaCoO have been studied from powder neutron diffraction. The compound crystallizes in 2 5˚˚t he orthorhombic space group Pnma, with lattice parameters: a512.1745(2) A, b55.6594(1) A, c56.9993(1) A. Bulk magnetic measurements reveal a jump in the temperature dependence of the susceptibility around 10 K, which corresponds to the antiferromagnetic 31 21 ordering of the Yb and Co sublattices which is fully confirmed with neutron diffraction data. From the later, a magnetic structure with an identical cell to the chemical one (k50) has been proposed to explain the onset of new reflections due to magnetic scattering that develop below T¯9.4 K. The spin arrangement is described on the basis of C A symmetry modes for all magnetic sublattices. © 1998 N x z Elsevier Science S.A.
Physical Review B, 2000
Electron paramagnetic resonance ͑EPR͒, optical absorption, fluorescence, and excitation spectra of CsCdBr 3 :1% Yb 3ϩ single crystals were taken at 4.2 K. An analysis of the dependence of the EPR spectrum on the magnetic-field direction and a comparison of the recorded signal shapes with simulated envelopes over the magnetic dipole transitions of the expected dimers containing all ytterbium isotopes were performed. This allowed us to assign the measured EPR spectra unambiguously to the symmetrical pair center of the type Yb 3ϩ -Cd 2ϩ vacancy-Yb 3ϩ substituting for three adjacent Cd 2ϩ ions in the bromine octahedra chains. A distance of 0.596 nm between the magnetically equivalent Yb 3ϩ ions was determined from the line splitting due to magnetic dipole-dipole interaction. An interpretation of the optical spectra in compounds containing ͑YbBr 6 ͒ 3Ϫ complexes is presented, which is based on a crystal-field theory accounting for an interaction between the ground 4 f 13 (Yb 3ϩ )͓4p 6 (Br Ϫ )͔ 6 and excited 4 f 14 (Yb 2ϩ )4p 5 (Br)͓4p 6 (Br Ϫ )͔ 5 charge-transfer configurations. The observed large splitting of the excited 2 F 5/2 (4 f 13 ) crystal-field multiplet is explained on the basis of a quasiresonant hybridization of the 4 f -hole state with the spin orbitals of the charge-transfer states. With physically reasonable values of the fitted model parameters, the calculated energy level diagram of the 4 f 13 configuration and the g tensor of the Yb 3ϩ ion in the crystal-field ground state are in good agreement with the experimental data.
Double rotation 11B NMR applied to polycrystalline barium borates
The potential of 11 B double rotation nuclear magnetic resonance to provide detailed structural information is demonstrated through the application of the technique to polycrystalline materials obtained by devitrification of barium diborate glasses. Isotropic chemical shift values and quadrupole interaction parameters for the four three-coordinated sites in α-BaB 4 O 7 are extracted by exploiting the field dependency of the quadrupolar interaction. The technique is applied to the polymorph β-BaB 4 O 7 , and two new barium borate materials of undetermined structure, and its role as a powerful structural probe is demonstrated and discussed.
Chemistry – A European Journal, 2021
The importance of equatorial crystal fields on magnetic anisotropy of ytterbium SMMs is observed for the first time. Herein, we report three similar dinuclear ytterbium complexes of formula [Yb2(3-OMe-L)2(DMF)2(NO3)2]•DMF (1), [Yb2(3-H-L)2(DMF)2(NO3)2]•DMF•H2O (2) and [Yb2(3-NO3-L)2(DMF)2(NO3)2] (3), [where 3-X-H2L= N'-(2-hydroxy-3-X-benzylidene)picolinohydrazide, X = OMe(1), H(2) NO2(3)]. The detailed magnetic measurements display the presence of weak antiferromagnetic interaction between the Yb centers and field induced slow relaxation of magnetization in all the complexes. The higher energy barrier for spin reversal was observed for complex 1 (Ueff = 50 K) and it dercreases in the order of 2 (47 K) to 3 (40 K). Notably, complex 1 shows a remarkable energy barrier with in the frequency range of 1-850 Hz reported for Yb-based single molecule magnets (SMMs). Further, the ab initio calculations show the higher axial anisotropy and lower QTM (quantum tunneling of magnetization) in the ground state for 1 compared to 2 and 3. It has also been observed that the presence of strong crystal field in the equatorial plane(when the O1-Yb-O3 bond angle is close to 90º) enhances the axial anisotropy and improve the SMM behavior in the studied complexes. Both the experimental and theoretical analysis of relaxation dynamics discloses that Raman and QTM play major role on slow relaxation process for all the complexes. To provide more insight into the exchange interaction the BS-DFT calculations were performed. Scheme 1. Represents the preparation of dinuclear ytterbium complexes with strong equatorial ligand field.
Zeitschrift für Naturforschung B, 2014
Transparent and colorless single crystals of Yb 26 B 12 O 57 were obtained by reacting Yb 2 O 3 and B powder at 1000 • C in the presence of a KCl flux for 24 h in silica-jacketed Nb ampoules and subsequent removal of the flux by washing with water. Yb 26 B 12 O 57 crystallizes in the monoclinic space group C2/m (no. 12, Z = 1) with the lattice parameters a = 2454.1(3), b = 357.78(4), c = 1426.7(2) pm and β = 115.111(6) • , and its structure differs slightly from that of a known compound with the same stoichiometry. Raman spectra of single crystals of the title compound were recorded and compared to those of known borate compounds.
On the boron rich phases in the Yb-B system
Journal of Solid State Chemistry
Two boron rich phases were successfully synthesized by borothermal reduction of Yb oxide under vacuum. For the new boron-poorer phase, the single phase was established at around [B]/[Yb]=43.3 at 1500 °C (Pbam space group; YB 50-type; a=16.5811(5) Å, b=17.5950(5) Å, c=9.4647(3) Å; powder X-ray diffraction; Rietveld refinement). The crystal structure of the boron-richer phase ([B]/[Yb]=56.0) has been elucidated by single crystal X-ray diffraction (3 Fm c space group; YB 66-type; a=23.3587(6) Å). Powder X-ray diffraction data of the alloy YbB~7 0 annealed at 1825 °C yielded, along with the YB 66-type compound (a=23.3691(2) Å), β-rh B as a secondary phase (m R3 space group, a=10.9298(3) Å, c=23.875(1) Å), for which the solubility of Yb was found to be below 1 at.%. Both YbB 43.3 and YbB 56.0 feature complicated boron atom frameworks which exhibit shorter B-B separations both within and between boron clusters as compared to those observed for prototype structures.
Investigations of the magnetic properties of the Yb6Mn23 intermetallic compound
Journal of the Less Common Metals, 1984
The magnetic properties of the Yb,Mn,, intermetallic compound were investigated using magnetometry and neutron diffraction. The Yb,Mn,, phase was found to have a ferrimagnetic structure. The magnetic and chemical unit cells of the compound coincide and the Curie point is 406 K. Neutron diffraction and magnetic measurements at low temperatures indicate that the ytterbium sublattice magnetization rapidly compensates the manganese sublattice magnetization.
Inorganic Chemistry, 2005
Despite the prevalent belief about a strong anisotropy of the magnetic exchange in rare-earth compounds, Cs 3-Yb 2 Cl 9 and Cs 3 Yb 2 Br 9 crystals are found to exhibit fully isotropic exchange coupling between Yb 3+ ions. In this article, we attempt to reveal the physical origin of this surprising feature. Our theoretical consideration is based on a model of the kinetic exchange between two octahedrally coordinated Yb 3+ ions in their ground Kramers doublet states. It is shown that a mechanism of kinetic exchange involving intercenter electron hopping between 4f orbitals of two Yb 3+ ions in a face-shared binuclear unit results in fully isotropic antiferromagnetic exchange coupling, while a mechanism in which the electron jumps from the 4f to the 5d orbital gives rise to a highly anisotropic interaction. Comparison of these results with the experimental data along with qualitative arguments regarding the relative significance of these two contributions to the overall exchange indicate that, in face-shared Yb 3+ binuclear units, the 4f T 4f mechanism plays a dominant role.
Crystal structure and magnetism of the Y2Pd14B5 compound
Journal of Alloys and Compounds, 2003
3˚T he crystal structure of the ternary boride Y Pd B , space group I4 /amd, a 5 8.484(2) A, c 5 16.490(3) A, V 5 1186.98 A , Z 5 4, 2 14 5 1 was refined down to R 5 0.0475, wR2 5 0.1276 from single crystal X-ray diffraction data. Two types of coordination for boron atoms were observed: the coordination sphere for the B1 atom is a trigonal prism with one additional atom; the B2 atom has only four neighboring atoms which form a square. No boron-boron contact was observed. Analysis of the Y Pd B crystal structure shows the 2 14 5 existence of a correlation between this structure and the Sc Ni B structure type. Magnetization and AC susceptibility measurements 4 29 10 indicate that there is no superconducting or magnetic transition in Y Pd B down to 2 K.