Hybrid electrons in the trimerized GaV4O8

Mixed-valent transition-metal compounds display complex structural, electronic and magnetic properties, which often intricately coexist. Here, we report the new ternary oxide GaV₄O₈, a structural sibling of skyrmion-hosting lacunar spinels. GaV₄O₈ contains a vanadium trimer and an original spin-orbital-charge texture that forms upon the structural phase transition at T_S = 68 K followed by the magnetic transition at T_N = 35 K. The texture arises from the coexistence of orbital molecules on the vanadium trimers and localized electrons on the remaining vanadium atoms. Such hybrid electrons create opportunities for novel types of spin, charge, and orbital order in mixed-valent transition-metal compounds.

Strongly reduced lattice thermal conductivity in Sn-doped rare-earth (M) filled skutterudites M x Co4Sb12-y Sn y , promoted by Sb-Sn disordering and phase segregation

CoSb3 thermoelectric skutterudite has been filled with rare-earth metals (M = La, Ce, Yb) and partially doped with Sn in specimens of M x Co4Sb12-y Sn y stoichiometry. This has been achieved under high-pressure conditions at 3.5 GPa in a piston-cylinder hydrostatic press. A structural investigation using synchrotron X-ray diffraction data reveals a phase segregation in twin skutterudite phases with filling fraction fluctuation and different unit-cell sizes. As a result of three effects acting as phonon scatterers, namely the rattling effect of M at the wide 8a cages of the cubic Im3̄ structure, the phase segregation, and the intrinsic disorder introduced by Sn substitution at the Sb sublattice, the total thermal conductivity (κ) dramatically falls to reach minimum values under 2 W m-1 K-1, well below those typically exhibited by other thermoelectric materials based upon single-filled skutterudites. The power factor is substantially enhanced to 1.11 mW m-1 K-2 in Yb0.5Co4Sb11.6Sn0.4 with respect to the unfilled composition, as a result of the charge transfer promoted by the filler.

Operando Synchrotron X-ray Diffraction in Calcium Batteries: Insights into the Redox Activity of 1D Ca3CoMO6 (M = Co and Mn)

1D Ca₃Co_2-z M _z O₆ (M = Co z = 0, M = Mn z = 1, and M = Fe z = 0.4) were prepared and tested electrochemically. While the iron-containing phase was not found to be active, the iron- and manganese-containing phases were found to be potentially interesting as positive electrode materials for calcium metal-based high-energy battery technologies and were investigated by operando synchrotron X-ray diffraction. Results indicate that electrochemically driven calcium deintercalation from the crystal structure (ca. 0.7 mol per formula unit) takes place upon oxidation in both cases. The oxidized phases have incommensurate modulated crystal structures with the space group R 3m(00γ)0s and a = 9.127(1) Å, c ₁ = 2.4226(3) Å and c ₂ = 4.1857(3) Å, and γ = 0.579 (M = Co) and a = 9.217(1) Å, c ₁ = 4.9076(4) Å and c ₂ = 4.3387(4) Å, and γ = 1.139 (M = Mn), which exhibit differences due to the presence of manganese and Mn/Co ordering. The degree of calcium re-intercalation within the structure was found to be extremely limited, if any. Complementary experiments carried out in lithium cells did not show any reversibility either, thus pointing at intrinsic structural/migration constraints in the oxidized phase rather than slow kinetics of high desolvation energies associated with divalent ion charge carriers.

Structural Features, Anisotropic Thermal Expansion, and Thermoelectric Performance in Bulk Black Phosphorus Synthesized under High Pressure

Black phosphorus (BP) allotrope has an orthorhombic crystal structure with a narrow bandgap of 0.35 eV. This material is promising for 2D technology since it can be exfoliated down to one single layer: the well-known phosphorene. In this work, bulk BP was synthesized under high-pressure conditions at high temperatures. A detailed structural investigation using neutron and synchrotron X-ray diffraction revealed the occurrence of anisotropic strain effects on the BP lattice; the combination of both sets of diffraction data allowed visualization of the lone electron pair 3s². Temperature-dependent neutron diffraction data collected at low temperature showed that the a axis (zigzag) exhibits a quasi-temperature-independent thermal expansion in the temperature interval from 20 up to 150 K. These results may be a key to address the anomalous behavior in electrical resistivity near 150 K. Thermoelectric properties were also provided; low thermal conductivity from 14 down to 6 Wm^-1K^-1 in the range 323-673 K was recorded in our polycrystalline BP, which is below the reported values for single-crystals in literature.

Electronic and Magnetic Properties of Cation Ordered Sr2Mn2.23Cr0.77As2O2

Several different mechanisms of magnetoresistance (MR) have been observed in 1111 LnMnAsO_1-xF_x oxypnictides (Ln = lanthanide) as a result of magnetic coupling between the Mn and Ln. Such phases also exhibit interesting magnetic phase transitions upon cooling. Sr₂Mn₂CrAs₂O₂ has been synthesized to investigate if it is possible to observe MR and/or magnetic phase transitions as a result of magnetic coupling between the Mn and Cr. Sr₂Mn₂CrAs₂O₂ crystallizes in the tetragonal space group I4/mmm containing alternating MO₂^2- and M'₂As₂^2- layers, and neutron diffraction results demonstrate that the actual stoichiometry is Sr₂Mn_2.23Cr_0.77As₂O₂. Cation order is present between Mn and Cr, with Cr predominantly occupying the square planar MO₂^2- site. Below 410 K, the magnetic moments of the Mn/Cr ions in the M'₂As₂^2- sublattice exhibit G-type antiferromagnetic order. The Mn/Cr moments within the MO₂^2- layer order below 167 K with a K₂NiF₄-type antiferromagnetic structure that simultaneously induces a spin flip of the magnetic moments in the M'₂As₂^2- layers from a G-type to a C-type antiferromagnetic arrangement. The results demonstrate that the superexchange interactions are finely balanced in Sr₂Mn_2.23Cr_0.77As₂O₂. Sr₂Mn_2.23Cr_0.77As₂O₂ is semiconducting, and there is no evidence of MR.

Octupolar versus Néel Order in Cubic 5d^{2} Double Perovskites

We report time-of-flight neutron spectroscopy and neutron and x-ray diffraction studies of the 5d^{2} double perovskite magnets, Ba_{2}MOsO_{6} (M=Zn,Mg,Ca). These materials host antiferromagnetically coupled 5d^{2} Os^{6+} ions decorating a face-centered cubic (fcc) lattice and are found to remain cubic down to the lowest temperatures. They all exhibit thermodynamic anomalies consistent with a single phase transition at a temperature T^{*}, and a gapped magnetic excitation spectrum with spectral weight concentrated at wave vectors typical of type-I antiferromagnetic orders. However, while muon spin resonance experiments show clear evidence for time-reversal symmetry breaking below T^{*}, we observe no corresponding magnetic Bragg scattering signal. These results are shown to be consistent with ferro-octupolar symmetry breaking below T^{*}, and are discussed in the context of other 5d double perovskite magnets and theories of exotic orders driven by multipolar interactions.

Crystal structure features of CH3NH3PbI3−xBrx hybrid perovskites prepared by ball milling: a route to more stable materials

Hybrid organic–inorganic perovskites, MAPbX₃ (MA: CH₃–NH₃⁺; X = halogen), prepared by ball milling are, by far, much more stable towards ambient conditions (air, humidity) than the conventional materials prepared from solution chemistry.

Magnetostructural behavior in the non-centrosymmetric compound Nd7Pd3

A systematic study of the physical properties and microscopic magnetism of Nd₇Pd₃ compound, which in the paramagnetic state crystallizes in the non-centrosymmetric hexagonal Th₇Fe₃-type structure (hP20-P6₃ mc; with a  =  10.1367(1) Å and c  =  6.3847(1) Å at 300 K), confirms multiple magnetic ordering transitions that occur upon cooling. Antiferromagnetic transition is observed at T _N  =  37 K, which is followed by ferromagnetic transformation at T _C  =  33 K. The first-order magnetic transition at T _C is magnetoelastic: it involves a change of crystal symmetry from P6₃ mc to Cmc2₁ and leads to anisotropic changes of the unit cell parameters. While the antiferromagnetic structure is symmetry allowed in P6₃ mc, the ferromagnetic structure with magnetic moments along the a-direction of the original hexagonal unit cell induces the first order transition to Cmc2₁. Density functional theory calculations confirm the experimentally observed ground state with the a-axis as the easy magnetization direction.

Disclosing odd symmetry, strain driven magnetic response of Co on Pt/PMN-PT (0 1 1)

An odd-symmetry magnetic response of multiferroic composites comprising ultrathin Co layers on Pt electrodes on [Pb(Mg_0.33Nb_0.67)O₃]_(1-x)[PbTiO₃] _x (PMN-PT) (0 1 1) piezoelectric substrates is observed upon electrical poling of the PMN-PT substrates: the magnetic easy axis of the Co rotates by 90° in-plane between oppositely poled ferroelectric states, mimicking the signature of a surface polarization charge driven effect, which however can be excluded from the presence of the thick Pt interlayer. The origin for this unexpected behavior is as an odd symmetry piezoelectric response of the PMN-PT substrate, as indicated by x-ray diffraction with applied poling, in combination with conventional magnetoelastic coupling. Ferroelectric characterization reveals corresponding features, possibly related to an unswitchable polarization component.

In Operando Synchrotron Diffraction and in Operando X-ray Absorption Spectroscopy Investigations of Orthorhombic V2O5 Nanowires as Cathode Materials for Mg-Ion Batteries

Orthorhombic V₂O₅ nanowires were successfully synthesized via a hydrothermal method. A cell-configuration system was built utilizing V₂O₅ as the cathode and 1 M Mg(ClO₄)₂ electrolyte within acetonitrile, together with Mg _xMo₆S₈ ( x ≈ 2) as the anode to investigate the structural evolution and oxidation state and local structural changes of V₂O₅. The V₂O₅ nanowires deliver an initial discharge/charge capacity of 103 mAh g^-1/110 mAh g^-1 and the highest discharge capacity of 130 mAh g^-1 in the sixth cycle at C/20 rate in the cell-configuration system. In operando synchrotron diffraction and in operando X-ray absorption spectroscopy together with ex situ Raman and X-ray photoelectron spectroscopy reveal the reversibility of magnesium insertion/extraction and provide information on the crystal structure evolution and changes of the oxidation states during cycling.

Synthesis, Structure, and Physical Properties of the Polar Magnet DyCrWO6

It has recently been reported that the ordered aeschynite-type polar ( Pna2₁) magnets RFeWO₆ (R = Eu, Tb, Dy, Y) exhibit type II multiferroic properties below T_N ∼ 15-18 K. Herein, we report a comprehensive investigation of the isostructural oxide DyCrWO₆ and compare the results with those of DyFeWO₆. The cation-ordered oxide DyCrWO₆ crystallizes in the same polar orthorhombic structure and undergoes antiferromagnetic ordering at T_N = 25 K. Contrary to DyFeWO₆, only a very weak dielectric anomaly and magnetodielectric effects are observed at the Néel temperature and, more importantly, there is no induced polarization at T_N. Furthermore, analysis of the low-temperature neutron diffraction data reveals a collinear arrangement of Cr spins but a noncollinear Dy-spin configuration due to single-ion anisotropy. We suggest that the collinear arrangement of Cr spins may be responsible for the absence of electric polarization in DyCrWO₆. A temperature-induced magnetization reversal and magnetocaloric effects are observed at low temperatures.

Elucidating the Methylammonium (MA) Conformation in MAPbBr3 Perovskite with Application in Solar Cells

Hybrid organic-inorganic perovskites, MAPbX₃ (X = halogen), containing methylammonium (MA: CH₃-NH₃⁺) in the large voids conformed by the PbX₆ octahedral network, are the active absorption materials in the new generation of solar cells. CH₃NH₃PbBr₃ is a promising member with a large band gap that gives rise to a high open circuit voltage. A deep knowledge of the crystal structure and, in particular, the MA conformation inside the perovskite cage across the phase transitions undergone below room temperature, seems essential to establish structure-property correlations that may drive to further improvements. The presence of protons requires the use of neutrons, combined with synchrotron XRD data that help to depict subtle symmetry changes undergone upon cooling. We present a consistent picture of the structural features of this fascinating material, in complement with photocurrent measurements from a photodetector device, demonstrating the potential of MAPbBr₃ in optoelectronics.

In operando X-ray diffraction of lithium–oxygen batteries using an ionic liquid as an electrolyte co-solvent

Chemical instability of ionic liquids in the presence of lithium metal leading to spontaneous LiOH formation.

A novel high-throughput setup forin situpowder diffraction on coin cell batteries

A new setup forin situexperiments with up to eight electrochemical cells, especially battery coin cells, and the corresponding custom-madein situcells are presented. The setup is primarily optimized for synchrotron powder diffraction measurements. As a newly constructed experimental setup, thein situcoin cell holder was tested for positional errors of the cells and the reliability of the diffraction as well as electrochemical measurements. The overall performance characteristics of the sample holder are illustrated by measurements on LiMn2O4and LiNi0.35Fe0.3Mn1.35O4spinel-based positive electrode materials.

Phase II study of bendamustine in combination with rituximab as first-line treatment in patients 80 years or older with aggressive B-cell lymphomas

BACKGROUND

Rituximab plus combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) is widely recommended for the treatment of aggressive B-cell lymphomas. However, there is very little information regarding the management of elderly patients.

PATIENTS AND METHODS

We initiated a phase II study of first-line treatment with rituximab and bendamustine in elderly patients (≥80 years) with aggressive B-cell lymphomas who were not eligible for R-CHOP or who did not agree to aggressive treatment. The treatment decision on eligibility for R-CHOP was left to discretion of the physicians.

RESULTS

Fourteen patients with a median age of 85 years (range 80-95 years) were included. The age-adjusted international prognostic index was zero in five patients, one in three patients, and two in six patients. Thirteen patients were assessable for response. Seven patients (54%) had a complete response, two (15%) a partial response, and four (31%) progressive disease. The median overall survival was 7.7 months, and the median progression-free survival 7.7 months; however, six patients (43%) were alive without disease at 20-72 months from the start of treatment. Major toxicity was neutropenia (17% grade 3 and 6% grade 4). All other grade 3 and 4 hematotoxicities and non-hematological toxic effects ranged between 2% and 11%

CONCLUSIONS

Because of its efficacy and low toxicity, bendamustine in combination with rituximab may be an alternative treatment for aggressive lymphomas in old patients not eligible for R-CHOP. These results, however, need to be confirmed in larger studies.

Enhancement of antiferromagnetic coupling in magnetic multilayers by low energy ion beam substrate nanopatterning

Ion beam irradiation has been shown to be an interesting tool for tailoring the magnetic properties of thin films and multilayers. The modified properties include magnetic anisotropy, interlayer exchange coupling, exchange bias, magnetic domain structure and magnetization reversal. In this work, new results are shown concerning the enhancement, by one order of magnitude, of the antiferromagnetic coupling strength in amorphous CoSi/Si multilayers by irradiating Si(100) substrates with 1 keV Ar(+) ions. The ion beam exposure induces an increase of the substrate roughness, from 0.07 to 0.88 nm, which enhances antiferromagnetic coupling in the magnetic multilayers grown on top. One possible mechanism governing this enhancement is discussed, related to the formation of magnetic/non-magnetic regions where dipolar interactions could stabilize the antiferromagnetic alignment. The presence of non-magnetic regions is suggested by the observed trend to superparamagnetism, and is expected since the Curie temperature of the amorphous CoSi alloy used is slightly above but very close to room temperature. Accordingly, small fluctuations in the local composition, leading to an enrichment of Si, would produce non-magnetic regions enabling dipolar interactions to take place. Furthermore, the ion beam induced increase of roughness makes surface diffusion of the atoms arriving at the sample difficult, favoring the formation of local non-magnetic inhomogeneities. Finally, the role of other possible mechanisms to enhance antiferromagnetic coupling is also briefly discussed.

[The infammatory pseudotumour -- an unusual liver tumour]

We report on a 49-year-old male patient who was suspected to have a malignant liver tumour with enlarged perihepatic lymph nodes because of CT and ultrasound scanning. To verify the diagnosis and procure a histological specimen, the patient underwent laparotomy. Histologically, an inflammatory pseudotumour could be confirmed. This is a rare disease which can present with fever, abdominal pain, vomiting and weight loss indicating malignancy or abscess. The definite diagnosis is often only verified by surgery.

Direct observation of charge order in an epitaxial NdNiO3 film

The first direct observation of charge order of Ni(3+delta(')) and Ni(3-delta) by resonant x-ray scattering experiments in an epitaxial film of NdNiO3 is reported. A quantitative value of delta+delta(') = (0.45 +/- 0.04)e was obtained. The temperature dependence of the charge order deviates significantly from those of the magnetic moment and crystallographic structure. This might be an indication of a difference in their fluctuation time scales. These observations are discussed in terms of the temperature-driven metal-insulator transition in the RNiO3 family.

AC133 expression on acute myeloid leukemia blasts: correlation to FAB and to CD34 expression and possible implications for peripheral blood progenitor cell purging in AML

AC133 is an antigen expressed on CD34+ hematopoietic progenitor cells. In acute myeloid leukemia (AML) it is expressed on leukemic blasts of most FAB subtypes. However, few data are available regarding coexpression of other surface antigens. We measured AC133 expression on AML blasts from 28 consecutive patients at initial diagnosis (n=26) or at diagnosis of first relapse (n=2) and on 26 leukapheresis products from 14 patients. In AML AC133 correlated with CD34 expression (Spearman r=0.4711, P=0.0114) and even stronger with combined CD34/CD33 expression (Spearman r=0.5083, P=0.0068). In leukapheresis products AC133 expression correlated with CD34 expression (Spearman r=0.7495, P=0.002) and the yield of the obtained amount of CD34+ cells (Spearman r=0.6484, P=0.0121). In conclusion AC133 expression is closely related to CD34 expression in AML. In leukapheresis products AC133 provides an additional marker for selection of PBPC autografts in AC133- AML.

Purging of G-CSF-mobilized peripheral autografts in acute leukemia with mafosfamide and amifostine to protect normal progenitor cells

In the present study the in vitro growth of CFU-GM from PBPC of patients with AML (n = 11), purged with mafosfamide alone or a combination of mafosfamide and amifostine, was compared to historical controls of mafosfamide-purged bone marrow (AML CR1, n = 16). Two patients were transplanted with mafosfamide and mafosfamide/amifostine pretreated PBPC autografts. The in vitro experiments demonstrated a significantly higher resistance of peripheral blood derived CFU-GM to mafosfamide (median ID95 190 microg mafosfamide/ml) compared with bone marrow derived CFU-GM (median ID95130 microg/ml). Preincubation with amifostine significantly further increased the median ID95 to 245 microg/ml. The clinical results showed short recovery times for neutrophils >500/microl (9 and 13 days) and platelets >20 000/microl (12 and 21 days) and stable long-term engraftment with one relapse at day +118 and one patient in CR at day 760 after transplantation. The in vitro results show a significant advantage of PBPC over bone marrow-derived progenitors for purging with mafosfamide. Furthermore, a protective effect from mafosfamide of amifostine on normal progenitors could be demonstrated. The clinical results demonstrate the clinical feasibility of using mafosfamide-purged autologous PBPCT without impairing the short-term and long-term repopulating capacities of the autografts.

Purging in BCR-ABL-positive acute lymphoblastic leukemia using immunomagnetic beads: comparison of residual leukemia and purging efficiency in bone marrow vs peripheral blood stem cells by semiquantitative polymerase chain reaction

Twenty autologous bone marrow (BM) and 25 peripheral blood stem cell (PBSC) grafts were collected from a total of 40 consecutive patients with BCR-ABL+ acute lymphoblastic leukemia (ALL) in first (n = 37) or second (n = 3) complete morphological remission and subsequently purged with a cocktail of anti-CD19, -CD10, AB4 MoAbs and immunomagnetic beads (IMB). Residual BCR-ABL-positive cells before purging were detected in 19 of 20 BM grafts at a median of 4 (range 0-6) logs and in 17 of 25 evaluable PBSC grafts at a median of 1 (range 0-3) log above the limit of detection assessed by a semiquantitative limiting log10-dilution RT-PCR (P < 0.0001). IMB purging depleted a median of 2.5 (range 1-4) log of residual BCR-ABL+ cells from BM and a median of 1 (range 0-2) log from PBSC grafts, achieving RT-PCR negativity in 1/20 BM and 12/25 PBSC grafts after purging. Cell recoveries were 62% and 86% (P < 0.0001) of MNC and 74% and 97% (P = 0.065) of CD34+ cells after BM and PBSC purging, respectively. BM purging was superior using the triple MoAb cocktail which depleted 2.64 +/- 0.4 log (n = 14) compared to 1.6 +/- 0.4 log (n = 5) using the MoAb cocktail not including AB4 (P = 0. 02). We conclude that unpurged BM grafts contain 2-3 log more residual BCR-ABL+ cells than unpurged PBSC grafts and that purging efficacy is superior in BM compared to PBSC grafts, but median titers in purged BM grafts still exceed those in purged PBSC grafts. Bone Marrow Transplantation (2000) 25, 97-104.