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A complex optimization of the arc melting synthetic approach was performed to enhance the phase purity of Cr2AlC MAX-phase in the bulk form. Optimization steps included the initial ratio of 2Cr: xAl: 1C, variation through a change in Al content (i.e. x ranging from 1 to 1.5), tuning duration of the post-annealing thermal treatment and adjustment of the melting chamber pressure. The use of Cr3C2 as a precursor in place of Cr and C mixture has also been tried. It was found that Cr2AlC MAX-phase forms as the predominant phase when a stoichiometric ratio 2Cr: 1.3Al: 1C is used. By keeping this stoichiometry constant, the melting chamber pressure was then adjusted to further improve the phase purity of the samples. It has been established that the use of Cr3C2 is not an appropriate way to improve sample purity and promote homogeneity in the carbon distribution. The establishment of an optimized arc fusion protocol for parental Cr2AlC is a necessity for further successful mass synthesis of the substituted (Cr1-xMnx)2AlC MAX-phase.

The electronic ground state of iron-based materials is unusually sensitive to electronic correlations. Among others, its delicate balance is profoundly affected by the insertion of magnetic impurities in the FeAs layers. Here, we address the effects of Fe-to-Mn substitution in the non-superconducting Sm-1111 pnictide parent compound via a comparative study of SmFe1-xMnxAsO samples with x(Mn) = 0.05 and 0.10. Magnetization, Hall effect, and muon-spin spectroscopy data provide a coherent picture, indicating a weakening of the commensurate Fe spin-density-wave (SDW) order, as shown by the lowering of the SDW transition temperature TSDW with increasing Mn content, and the unexpected appearance of another magnetic order, occurring at T∗≈ 10 and 20 K for x= 0.05 and 0.10, respectively. We attribute the new magnetic transition at T∗, occurring well inside the SDW phase, to a reorganization of the Fermi surface due to Fe-to-Mn substitutions. These give rise to enhanced magnetic fluctuations along the incommensurate wavevector Q2= (π± δ, π± δ) , further increased by the RKKY interactions among Mn impurities., Scientific Reports, 11, ISSN:2045-2322

The local structure of La(Fe1-xMnx)AsO, showing suppression of long-range magnetic order by Mn-substitution, has been studied. Extended X-ray absorption fine structure (EXAFS) measurements at As K-edge and Fe K-edge are used to probe the atomic correlations in the FeAs-layer. We have found that both Fe-As and Fe-Fe bondlengths tend to increase with increasing Mn concentration. The associated mean square relative displacements (MSRD) reveal a gradual increase indicating increased local disorder in the FeAs-layer with Mn content. The results reveal that the FeAs-layer thickness, measured by the As-height (hAs) from the Fe-Fe plane, is correlated with the Neel temperature. Furthermore, Fe Kβ X-ray emission spectroscopy (XES) shows a sharp increase in the Fe local magnetic moment with Mn substitution. The importance of the FeAs layer thickness in describing magnetic correlations in La(Fe1−xMnx)AsO is discussed.

A study on the formation and stability of new quaternary compounds with the general chemical formula Gd3TAl3Ge2(T = Mn, Cu) has been undertaken by experimental investigations (SEM-EDX, DTA and XRD) and density functional theory (DFT) calculations. These compounds crystallize in the hexagonal Y3NiAl3Ge2-type structure (hP9, P–62m, Z = 1) (an ordered, quaternary derivative of the ternary ZrNiAl or of the binary Fe2P prototypes), with lattice parameters values a = 7.0239(2) Å and c = 4.2580(1) Å for Gd3MnAl3Ge2and a = 7.0434(1) Å and c = 4.2089(1) Å for Gd3CuAl3Ge2. DTA suggests a peritectic reaction for the formation of these compounds (at 1245°C for Gd3CuAl3Ge2). The existence and stability of these phases has been explained on the basis of DFT calculations, and a comparison of ground state properties of the studied compounds with the earlier known Gd3CoAl3Ge2phase is outlined. The negative formation energies in all three cases govern the stability of compounds from theory as well, predicting Gd3MnAl3Ge2as the most stable phase with highest formation energy (–13.01 eV/f.u.). The total DOS are generic in nature and suggest the robust magnetism, with the Gd-f moments of ≈7 μB. An antiparallel coupling among Gd-f and T-d states is observed for all compounds, as usually seen in rare earth (R) - transition metal (T) compounds. Preliminary magnetization measurements on Gd3MnAl3Ge2show two ferromagnetic/ferrimagnetic (FM/FIM) like transitions at TC1= 142 K and TC2= 97 K, with another anomaly seen at ≈15 K. Isothermal magnetization data show no hysteresis even at 5 K, and the magnetization does not saturate up to 50 kOe, further suggesting a possible FIM behavior.

The R 3TiSb5 ternary compounds, with R a light rare earth (La to Sm) have been reported to crystallize with the anti-Hf5CuSn3-type hexagonal structure (Pearson’s symbol hP18; space-group P63/mcm, N. 193). An early article that reported possible superconductivity in some of these intermetallic phases (namely those with R = La, Ce, and Nd) caught our attention. In this work, we have now refined the crystal structure of the R 3TiSb5 compounds with R = Ce, Pr and Nd by Rietveld methods using high-resolution neutron powder diffraction data. The magnetic ground states of these intermetallics have been investigated by low-temperature magnetization and high-intensity neutron diffraction. We find two different magnetic transitions corresponding to two related magnetic structures at T N1 = 4.8 K (k 1 = [0, 1/2, 1/8]) and T N2 = 3.4 K (k 2 = [0, 0, 1/8]), respectively for Ce3TiSb5. However, the magnetic ordering appears to occur following a peculiar hysteresis: the k 2-type magnetic structure develops only after the k 1-type phase fraction has first slowly ordered with time and the size of the ordered Ce3+ magnetic moment has become large enough to induce the second magnetic transition. At T = 1.5 K the maximum amplitude of the Ce moment in the coexisting phases amounts to μ Ce = 2.15 μ B. For Nd3TiSb5 an antiferromagnetic ordering below T N = 5.2 K into a relatively simpler commensurate magnetic structure with a magnetic moment of μ Nd = 2.14(3) μ B and magnetic propagation vector of k = [0, 0, 0], was determined. No evidence of superconductivity has been found in Nd3TiSb5. Finally, Pr3TiSb5 does not show any ordering down to 1.5 K in neutron diffraction while an antiferromagnetic ground state is detected in magnetization measurements. There is no sign of magnetic contribution from Ti atoms found in any of the studied compounds.

International audience; We report a small-core UV-grade silica multimode photonic crystal fiber for nonlinear frequency conversion in the ultraviolet spectral region. The fiber has been fabricated using F110 UV-Grade glass from Heraeus, which features excellent transmission and low solarization in the UV window. Pumping the fiber core at 355 nm with picosecond laser pulses, we observe the appearance of parametric sidebands in several spatial modes up to 380 nm. We modelled this process using intermodal phase-matching conditions and obtained excellent agreement between calculations and the measured data. We further report frequency conversion pumping into the fiber microstructured cladding where broadband cascaded Raman scattering spanning up to 391 nm is observed. These results represent a significant step towards the efficient and stable generation of UV supercontinuum spectra in an all-silica fiber platform.

In continuation of our studies on the binary RPd compounds (orthorhombic CrB-type structure, Pearson symbol oS8, space group Cmcm, No. 63), we report here the magnetic properties of the iso-structural PrPd and SmPd. The two compounds order ferromagnetically with the Curie temperature, TC, of nearly 12 K and 22 K, respectively (inferred from the peak temperature of the heat capacity at the paramagnetic to ferromagnetic transition). Anomalies in the magnetization and the electrical resistivity are also observed in correspondence of the bulk magnetic transition. The ferromagnetic nature of the magnetic transition is clearly indicated by the temperature and field dependence of the magnetization. The coercive fields of the two compounds are measured to be 160 Oe and 12 kOe at 2 K, respectively. The temperature dependence of both the heat capacity and electrical resistivity indicates a gapped ferromagnetic magnon spectrum with the gaps of ≈11 K and ≈40 K in PrPd and SmPd, respectively. The data obtained in current work are compared and discussed together with those previously reported for CePd and NdPd; the Curie temperatures of the four RPd iso-structural compounds follow the de Gennes scaling.

We have investigated the formation and stability of the binary rare-earth phases, previously reported in the literature as “RPd2”. Although these phases apparently showed a simple stoichiometry, their structure was not that of a Laves phase. After more than half of a century their crystal structure and true stoichiometry have been finally established. The exact stoichiometry of the “RPd2” phases is R10Pd21. The formation of the R10Pd21 compounds has been ascertained for R = Y, Pr, Nd, Sm, Gd to Lu, including Yb; Sc does not form the 10 : 21 phase. Pr10Pd21 forms only as a high temperature phase. These compounds crystallize in the monoclinic Sm10Pd21-type (mS124-C2/m, No. 12, Z = 4); the lattice parameters and unit cell volume decrease linearly on going from Pr to Lu in agreement with the lanthanide contraction. The crystal structure has been determined by X-ray powder diffraction and refined by Rietveld method for the Y, Nd, Tb and Lu compounds. These phases form by a peritectic reaction; the formation temperature, Tf, of some of them has also been measured and compared with the values reported for the “RPd2” phases for which the literature data are available. The increase of both the volume contraction and Tf on going from Pr10Pd21 to Lu10Pd21 suggests an increase of the thermodynamic stability along the series from the lighter to the heavier R. Physical properties (heat capacity, magnetic susceptibility and magnetization, electrical resistivity and magnetoresistance) have been measured for some members of the series (Nd10Pd21, Gd10Pd21, Tb10Pd21, Dy10Pd21, Ho10Pd21, Lu10Pd21 and Y10Pd21). Antiferromagnetic ordering is found for compounds with magnetic R ions at low temperature; the highest Neel temperature, TN, is 10 K for Tb10Pd21. The present experimental work represents a valuable contribution towards a more complete knowledge of the R–Pd systems. In the light of these results, all the binary R–Pd phase diagrams have to be reinvestigated (mainly those based on data assessed by the CALPHAD technique, using optimized thermodynamic parameters) and updated to furnish the material scientists consistent information to challenge the study of more complex systems.

A family of novel intermetallic R3CoNi with heavy rare earth ions has been synthesized (R = Tb, Dy, Ho, Er, Tm, Lu) and a study of the crystal structure of these phases performed. All the compounds adopt the rhombohedral Er3Ni2-type structure [Pearson’s symbol hR45; space group R-3h (N. 148)]. A thorough investigation of their magnetic and magnetocaloric properties has been undertaken. Magnetization and ac-susceptibility measurements as a function of temperature show that the samples with Tb, Dy, Ho, Er, and Tm present a paramagnetic to ferromagnetic (PM-FM) transition at temperatures in the range 96–6 K; different reorientation transitions take place below the respective TC, in most cases with thermomagnetic irreversibility. Thermal and magnetic measurements have been used to retrieve the set of critical exponents (α, β, γ, δ) for the PM-FM transition to assign a universality class to Tb3CoNi, Dy3CoNi, and Ho3CoNi, with the result that, in the first case, it is close to the Mean Field model, in the second one it is between the Chiral Heisenberg and the XY-Chiral, and in the third one it is close to the XY-Chiral model. Therefore, in Tb3CoNi the transition is governed by long-range order interactions, whereas in Dy3CoNi and Ho3CoNi there must be some kind of frustrated non-collinear ferromagnetism. The magnetocaloric measurements in five members of the family indicate that all of them present highly competitive magnetocaloric properties in their respective temperature ranges, with high magnetic entropy changes (from 12.8 to 18.5 J/Kg.K at μ0ΔH = 5 T) and refrigerant capacities (from 412 to 699 J/Kg at μ0ΔH = 5 T). These results assess and highlight the applicative interest of these compounds, besides suggesting the possibility of tuning the range of the operating temperature by modifying the rare earth ion. Finally, universal curves for the magnetocaloric properties have been found for Tb3CoNi, Dy3CoNi, and Ho3CoNi; the scaling of the magnetocaloric variables confirms the validity of the assigned universality classes.

Single crystals of the new compound CeCu 0.18 Al 0.24 Si 1.58 have been grown by high-temperature solution growth method using a eutectic Al-Si mixture as flux. This compound is derived from the binary CeSi 2 (tetragonal α-ThSi 2 -type, Pearson symbol tI 12, space group I 4 1 /amd ) obtained by partial substitution of Si by Cu and Al atoms but showing full occupation of the Si crystal site (8 e ). While CeSi 2 is a well-known valence-fluctuating paramagnetic compound, the CeCu 0.18 Al 0.24 Si 1.58 phase orders ferromagnetically at T C =9.3 K. At low temperatures the easy-axis of magnetization is along the a- axis, which re-orients itself along the c -axis above 30 K. The presence of hysteresis in the magnetization curve, negative temperature coefficient of resistivity at high temperatures, reduced jump in the heat capacity and a relatively lower entropy released up to the ordering temperature, and enhanced Sommerfeld coefficient (≈100 mJ/mol K 2 ) show that CeCu 0.18 Al 0.24 Si 1.58 is a Kondo lattice ferromagnetic, moderate heavy fermion compound. Analysis of the high temperature heat capacity data in the paramagnetic region lets us infer that the crystal electric field split doublet levels are located at 178 and 357 K, respectively, and Kondo temperature (8.4 K) is of the order of T C in CeCu 0.18 Al 0.24 Si 1.58 .

International audience; A major challenge in supercontinuum (SC) generation is to overcome the shortcomings of existing fibre-based SC sources in the ultraviolet (UV) wavelength range below 400 nm [1]. There is particular need for broadband sources of UV light in applications such as multi-photon fluorescence microscopy for simultaneous coherent excitation of multiple fluorophores. However, UV generation in conventional silica-core fibres is extremely difficult because of factors such as material absorption, large normal dispersion, glass stability, power handling, and aging, and this has motivated much recent interest in the use of alternative approaches [2,3]. Although these results show great promise, compatibility with the ubiquitous silica platform remains a problem, and there is thus intense current interest in generating UV-light using modified UV-resistant silica glasses.

Formation, crystal structure, and macroscopic and microscopic magnetism of the binary $\mathrm{T}{\mathrm{b}}_{3}\mathrm{N}{\mathrm{i}}_{2}$ and derivative pseudobinary $\mathrm{T}{\mathrm{b}}_{3}\mathrm{C}{\mathrm{o}}_{x}\mathrm{N}{\mathrm{i}}_{2\ensuremath{-}x}$ phases have been investigated using an array of experimental methods. While $\mathrm{T}{\mathrm{b}}_{3}\mathrm{N}{\mathrm{i}}_{2}$ crystallizes in the monoclinic $\mathrm{D}{\mathrm{y}}_{3}\mathrm{N}{\mathrm{i}}_{2}$ structure type ($\mathit{mS}20, C2$/m), the substitution of Co for Ni results in a structural transition into the rhombohedral $\mathrm{E}{\mathrm{r}}_{3}\mathrm{N}{\mathrm{i}}_{2}$ type ($\mathit{hR}\mathrm{45}, R\overline{3}h$) at $x(\mathrm{Co})\ensuremath{\approx}0.34$ and beyond in the $\mathrm{T}{\mathrm{b}}_{3}\mathrm{C}{\mathrm{o}}_{x}\mathrm{N}{\mathrm{i}}_{2\ensuremath{-}x}$ system. In both the monoclinic and rhombohedral phases, the addition of Co leads to an anisotropic change of lattice parameters and unexpected reduction of the cell volume. Measurements of bulk properties reveal that these compounds order ferrimagnetically or ferromagnetically at about 100 K. Complex noncollinear ferromagnetic ordering in the Tb sublattices is weakly dependent on composition. For $x$ g 0.34 the long-range magnetic ordering leads to a strong anisotropic magnetostriction accompanied by a symmetry reduction from rhombohedral to triclinic.

A detailed study of the magnetocaloric properties of six compounds of the intermetallic family RTX (R = Nd, Gd; T = Sc, Ti; X = Si, Ge) has been undertaken: NdScSi, NdScGe, GdScSi, GdScGe, GdSc(Si0.5Ge0.5) and Gd(Sc0.5Ti0.5)Ge. The magnetic entropy changes at the Curie temperature TC and the refrigerant capacities signal that they are competitive magnetocaloric materials, showing that an improvement can be obtained by tuning the composition, as Gd(Sc0.5Ti0.5)Ge presents the best properties. These magnetocaloric variables fulfill the scaling equations with the critical parameters corresponding to the universality classes to which the ferromagnetic transitions belong (3D-XY, 3D-Heisenberg, Mean field). For each compound, a universal curve has been found for the rescaled magnetic entropy changes obtained at different applied fields, whose behavior at temperatures below TC indicate the relevance of taking into account the demagnetization field. Finally, it has been demonstrated that the rescaled magnetic entropy changes for the compounds which share the same universality class collapse onto a single universal curve.

The substitution of Mn for Fe on the sub-lattice in LaFeAsO has a remarkable impact on both structural and magnetic properties; for example, the structural and magnetic transition temperatures decrease of ~20 K in samples with a Mn-content as low as x = 0.01. Such a dramatic effect results from the high stability of the substituting Mn2+ ion (3d 5) in its high-spin state, which opposes any variation to its electronic state (configuration), perturbing thereby interactions within the Fe sub-lattice between the Fe ions surrounding the substituent. Several investigations ascertained that the structural transformation in LnFeAsO compounds (Ln: lanthanide) cannot be ascribed to lattice degrees of freedom, but rather to electronic or spin ones. In this context, even an extremely low concentration of Mn2+ ions diluted in the Fe sub-lattice produces a reduction of the electronic degree of freedom of the system, thus hindering the structural transformation and the magnetic transition.

The local structure of La(Fe1−x Mn x )AsO has been investigated using temperature dependent Fe K-edge extended x-ray absorption fine structure (EXAFS) measurements. The EXAFS data reveal distinct behavior of Fe–As and Fe–Fe atomic displacements with a clear boundary between x ⩽ 0.02 and x > 0.02. The Fe–As bondlength shows a gradual thermal expansion while the Fe–Fe bond manifests a temperature dependent anomaly at ∼180 K for x > 0.02. It is interesting to find characteristically different nature of Fe–As and Fe–Fe bondlengths shown by the temperature dependent mean square relative displacements. Indeed, the Fe–As bond, stiffer than that of the Fe–Fe, gets softer for x ⩽ 0.02 and hardly shows any change for x > 0.02. On the other hand, Fe–Fe bond tends to be stiffer for x ⩽ 0.02 followed by a substantial softening for x > 0.02. Such a distinction has been seen also in the As K-edge x-ray absorption near edge structure, probing local geometry around As atom together with the valence electronic structure. The results suggest that local atomic displacements by Mn substitution inducing increased iron local magnetic moment that should be the main reason for its dramatic effect in iron-based superconductors.

The equiatomic NdPd compound crystallizes in the orthorhombic CrB structure type ( oS 8, Cmcm , No. 63). The NdPd phase melts congruently at 1240 °C, as observed by differential thermal analysis; one further sharp thermal effect detected at 1040 °C is very likely due to a structural transition. We confirm the CrB prototype for the low-temperature form of NdPd. The lattice parameters of this compound are a =3.842(2) A, b =10.776(7) A, c =4.605(2) A, as obtained from Guinier powder pattern; those for the corresponding iso-structural LaPd compound, prepared as non-magnetic reference, are a =3.947(2) A, b =11.036(3) A, c =4.663(2) A. Despite the fact that NdPd has been known since long, its physical properties have not been investigated till date. Here we report the results of magnetization, heat capacity and electrical resistivity measurements performed on this compound. NdPd undergoes a single ferromagnetic transition close to 15 K, inferred from a sharp upturn in the magnetization at lower temperatures and from Arrott plots measured at selected temperatures between 1.9 and 18 K. The coercive field and remnant magnetization at 1.9 K are 320 Oe and 0.24 μ B /f.u., which become negligible at 15 K. A sharp peak in the heat capacity at ≈15 K confirms the bulk magnetic transition. Isothermal magnetization at 2 K shows a tendency to saturation, reaching a value of 1.9 μ B /f.u. at the maximum applied field of 70 kOe. The zero field resistivity shows an anomaly near 15 K, in correspondence with the magnetic and heat capacity data. A negative magnetoresistivity, typical of a ferromagnet, is observed in the magnetically ordered state in an applied magnetic field of 50 kOe. LaPd is a typical Pauli paramagnet with a Sommerfeld coefficient γ =3.9 mJ/mol K 2 .

The crystal structure, composition and physical properties of Gd3Ni2, which was earlier reported to exist in the Gd–Ni system without any details of its structure and properties, have been determined. This rare earth binary compound is a high-temperature phase: it forms via a peritectic reaction at 988 K (715 °C) and decomposes below ≈923 K (650 °C). The compound can be retained at room temperature as a metastable phase by quenching after high temperature annealing. Gd3Ni2 crystallizes in the monoclinic Dy3Ni2 structure type [mS20, C2/m (No. 12), Z = 4; with lattice parameters a = 13.418(3) A, b = 3.720(1) A, c = 9.640(2) A, β = 106.250(3)°]. Ni can be substituted by Co up to 50% (i.e. up to and including Gd3CoNi) with no change in the structural prototype; the substitution of Co for Ni stabilizes the R3CoxNi2−x phases down to room temperature. The crystal structure, magnetic properties and magnetocaloric effect (MCE) have been investigated for both Gd3Ni2 and the related Gd3CoxNi2−x solid solution alloys (0 ≤ x ≤ 1). The crystal structure of the Gd3CoNi is a ternary ordered derivative of the monoclinic Dy3Ni2-type, where Co fully occupies only one of the two 4i Wyckoff sites available for the transition metal. To the best of our knowledge, this is the first example of an intermetallic phase showing ordered site occupations by the chemically quite similar elements Co and Ni. All compounds show long range ferromagnetic ordering, with TC progressively increasing from 147 K (for Gd3Ni2) to 176 K (for Gd3CoNi) as a cubic function of the Co content. Evidence of Co contributing to the magnetic interactions in these compounds has been found. First-principles total energy calculations predicted the ordered occupation of Co and Ni at the crystallographic sites of Gd3CoNi, which was later confirmed by single crystal X-ray diffraction. The increased conduction electronic state (3d) exchange splitting at the Fermi level supports the experimentally observed enhanced Curie temperature in Gd3CoNi compared to Gd3Ni2.

In a recent work we have reported the formation and the crystal structure of the new family of compounds R3Pd5 (R = Sc, Y, Gd–Lu; Pu3Pd5-type, oS32, spacegroup 63, Cmcm). DFT calculations for Gd3Pd5 and heat capacity and magnetic measurements for Tb3Pd5, Dy3Pd5, Ho3Pd5 and Er3Pd5 were able to discriminate at least two distinct antiferromagnetic transitions at low temperatures; at the same time these data suggested these separate magnetic orderings to be likely associated to the two structurally different rare earth sublattices (4c and 8e, respectively). The magnetic structures of the R3Pd5 compounds, with R = Tb, Dy, Ho, Er, have been now investigated in this work. High-resolution and high-intensity neutron powder diffraction data were recorded for the four compounds of the series. The results reveal that the magnetic structures adopted are significantly diverse and their temperature dependence more complex than originally deduced from magnetic and heat capacity measurements. Tb3Pd5 is in fact the only of the four compounds where the rare earth sublattices order independently with two different magnetic propagation vectors on the two sites (k1 = [1 0 ½] for Tb2 and k2 = [kx 0 0] or k3 = [1 0 0] for Tb1). In Dy3Pd5 both sublattices follow the propagation vector k = [kx 0 0], with the second transition corresponding to a spin reorientation. In Ho3Pd5 ordering of both sublattices follow the k = [1 0 0] propagation vector; the second transition seen in the magnetic and heat capacity data corresponds to an accelerated increase in the magnetic moment of the Ho2 sublattice. The case of Er3Pd5 is special as it is the sole case where one of the rare earth sublattices does not order down to T = 1.5 K; here the second transition determined from the magnetic data corresponds to a change of the magnetic propagation vector from k1 = [kx 0 kz] to k2 = [1 0 0], both only acting on the Er2 sublattice. Irrespectively of the very similar structures not even two of the four studied R3Pd5 compounds show identical magnetic structures on either of the two sublattices. These strong variations have to be connected to changes in the RKKY interactions induced by the progressive filling of the f-orbitals of the heavy rare earth ions and the concomitant changes of the crystal electric fields.

Crystallographic, magnetic, electrical transport and thermodynamic properties of pseudo-binary Nd7Ni2Pd compound have been studied using temperature-dependent x-ray powder diffraction and physical property measurements. Compared to the ferromagnetic parent Nd7Pd3, the ground state of Nd7Ni2Pd is antiferromagnetic, and it exhibits strong metamagnetism. The measurements indicate two antiferromagnetic transitions in fields less than 8 kOe: a second-order paramagnetic to antiferromagnetic at TN2 = 29 K and a weak first-order antiferromagnetic to antiferromagnetic transition at TN1 = 24.5 K. The compound becomes ferromagnetic in fields of 8 kOe and higher with TC = 30 K. Temperature dependence of lattice parameters is anomalous, most prominently in the basal plane at ∼30 K; however, there is no detectable structural distortion or clear volume discontinuity around 25 K, suggesting a significant weakening of the first-order transition when compared to the binary Nd7Pd3.

International audience; We report on the modeling and characterization of a truly single-mode hollow-core antiresonant fiber with a transmission band covering part of the near-infrared spectral region. Measured losses are 0.075 dB/m and 0.052 dB/m at 1.55 µm and 2.0 µm respectively.

Optimal suppression of higher-order modes (HOMs) in hollow-core antiresonant fibers comprising a single ring of thin-walled capillaries was previously studied, and can be achieved when the condition on the capillary-to-core diameter ratio is satisfied (d/D&asymp, 0.68). Here we report on the conditions for maximizing the leakage losses of HOMs in hollow-core nested antiresonant node-less fibers, while preserving low confinement loss for the fundamental mode. Using an analytical model based on coupled capillary waveguides, as well as full-vector finite element modeling, we show that optimal d/D value leading to high leakage losses of HOMs, is strongly correlated to the size of nested capillaries. We also show that extremely high value of degree of HOM suppression (&sim, 1200) at the resonant coupling is almost unchanged on a wide range of nested capillary diameter dNested values. These results therefore suggest the possibility of designing antiresonant fibers with nested elements, which show optimal guiding performances in terms of the HOM loss compared to that of the fundamental mode, for clearly defined paired values of the ratios dNested/d and d/D. These can also tend towards a single-mode behavior only when the dimensionless parameter dNested/d is less than 0.30, with identical wall thicknesses for all of the capillaries.

A complete study on the critical behavior of the paramagnetic to ferromagnetic transition in intermetallics GdScSi, GdScGe, GdSc(Si0.5Ge0.5) and Gd(Sc0.5Ti0.5)Ge has been carried out by means of magnetic as well as calorimetric measurements, using a high resolution ac photopyroelectric technique. The critical exponents α, β, γ, δ and the ratio of the critical coefficients A+/A− have been independently obtained for the four samples. It has been proved that the magnetic interactions are short range as the values of the critical parameters correspond to the 3D-Heisenberg class, stating an isotropic ordering of the Gd spins. In some cases, there are small deviations of some of the critical parameters from the theoretical values which have been discussed on the basis of the variation of the d states hybridization between the rare earth and the transition metal, as well as the presence of small magnetocrystalline anisotropies arising from spin-orbit coupling effects.

We report on an experimental study on the structural and magnetic properties of the intermetallic compound CrAlGe. The material has been investigated in detail by x-ray diffraction, dc magnetization, ac susceptibility, and electrical resistivity measurements. X-ray diffraction and associated Rietveld analysis show that the compound crystallizes in the orthorhombic $\mathrm{TiS}{\mathrm{i}}_{2}\text{\ensuremath{-}}\mathrm{type}$ structure, with lattice parameters $a=4.7531(1)\phantom{\rule{0.16em}{0ex}}\AA{},\phantom{\rule{0.16em}{0ex}}b=8.2182(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, and $c=8.6951(1)\phantom{\rule{0.16em}{0ex}}\AA{}$. The magnetization measurements demonstrate that the alloy is ferromagnetic with a Curie temperature of ${T}_{\mathrm{C}}\ensuremath{\approx}80\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At 5 K the magnetization saturates at 50 kOe with a saturation moment of ${M}_{\mathrm{S}}=19\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/\mathrm{g}$. Below ${T}_{\mathrm{C}}$, the ac susceptibility data exhibit two distinct frequency dependent peaks, which are also strongly dependent on ac field amplitude and dc magnetic fields. The experimental results strongly suggest the coexistence of ferromagnetic and reentrant spin glass type states in CrAlGe, which is due to the effect of the structural disorder in the $16f$ site (mixed Al/Ge occupation) on the crystallographically ordered $8a$ site of Cr. To our knowledge, CrAlGe is the first example where such unusual magnetic behavior is brought about not by structural disorder on the site occupied by the magnetic atom, but is due to the disorder in the atomic sites of the neighboring atoms.

A new series of intermetallic compounds R3Au9Pn (R = Y, Gd–Tm; Pn = Sb, Bi) has been discovered during the explorations of the Au-rich parts of rare-earth-containing ternary systems with p-block elements. The existence of the series is strongly restricted by both geometric and electronic factors. R3Au9Pn compounds crystallize in the hexagonal crystal system with space group P63/m (a = 8.08–8.24 A, c = 8.98–9.08 A). All compounds feature Au-Pn, formally anionic, networks built up by layers of alternating edge-sharing Au@Au6 and Sb@Au6 trigonal antiprisms of overall composition Au6/2Pn connected through additional Au atoms and separated by a triangular cationic substructure formed by R atoms. From a first look, the series appears to be isostructural with recently reported R3Au7Sn3 (a ternary ordered derivative of the Cu10Sn3-structure type), but no example of R3Au9M is known when M is a triel or tetrel element. R3Au9Pn also contains Au@Au6Au2R3 fully capped trigonal prisms, which are found to be isostructur...

A complete critical behavior study of the paramagnetic to ferromagnetic transition in intermetallics NdScSi and NdScGe has been carried out by means of magnetic as well as calorimetric measurements. The critical exponents α , β , γ and δ have been independently obtained. For NdScSi they are α = −0.015, β = 0.339, γ = 1.297 and δ = 4.94, indicating that it belongs to the 3D-XY universality class, while for NdScGe they are close to the mean field model with α tending to zero, β = 0.446, γ = 1.146 and δ = 3.44. The change from short-range to long-range ordering is discussed in terms of the magnetism mechanisms.

In this Letter we report high-resolution synchrotron X-ray powder diffraction and transmission electron microscope analysis of Mn-substituted LaFeAsO samples, demonstrating that a static incommensurate modulated structure develops across the low-temperature orthorhombic phase, whose modulation wave-vector depends on the Mn content. The incommensurate structural distortion is likely originating from a charge-density-wave instability, a periodic modulation of the density of conduction electrons associated with a modulation of the atomic positions. Our results add a new component in the physics of Fe-based superconductors, indicating that the density wave ordering is charge-driven., Comment: To be published in the Physical Review Letters

An investigation on the ground state magnetism of CeScSi, CeScGe (tetragonal CeScSi-type, tI12, space group I4/mmm) by temperature-dependent powder neutron diffraction has been carried out, as debated and controversial data regarding the low temperature magnetic behaviours of these two compounds were reported. Our studies reveal that, while cooling, long-range magnetic ordering in CeScSi and CeScGe takes place by a two-step process. A first transition leads to a magnetic structure with the Ce moments aligned ferromagnetically onto two neighbouring tetragonal basal a-b planes of the CeScSi-type structure; the double layers are then antiferromagnetically coupled to each other along the c-axis. The transition temperature associated with the first ordering is T N ~ 26 K and T N ~ 48 K for the silicide and the germanide, respectively. Here the spin directions are rigorously confined to the basal plane, with values of the Ce magnetic moments of μ Ce = 0.8-1.0 μ B. A second magnetic transition, which takes place at slightly lower temperatures, results in a canting of the ordered magnetic moments out of the basal plane which is accompanied by an increase of the magnetic moment value of Ce to μ Ce = 1.4-1.5 μ B. Interestingly, the second magnetic transition leads to a structural distortion in both compounds from the higher-symmetry tetragonal space group I4/mmm to the lower-symmetry and triclinic I-1 (non-standard triclinic). Magnetic symmetry analysis shows that the canted structure would not be allowed in the I4/mmm space group; this result further confirms the structural transition. The transition temperatures T S from I4/mmm to I-1 are about 22 K in CeScSi and 36 K in CeScGe, i.e. well below the temperature of the first onset of antiferromagnetic order observed in this work (or below the ordering temperature, previously reported as either T C or T N). This result, along with the synchronism of the magnetic and structural transitions, suggests a magnetostructural origin of this structural distortion. We have also carried out powder neutron diffraction for LaScSi as a non-magnetically-ordering reference compound and compared the results with those of CeScSi and CeScGe compounds.

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) A and c = 6.3847(1) A 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.

International audience; A highly birefringent polarization-maintaining chalcogenide microstructured optical fiber (MOF) covering the 3-8.5 µm wavelength range has been realized for the first time. The fiber cross-section consists of 3 rings of circular air holes with 2 larger holes adjacent to the core. Birefringence properties are calculated by using the vector finite-element method and are compared to the experimental ones. The group birefringence is 1.5x10−3 and fiber losses are equal to 0.8 dB/m at 7.55 µm.

The vaporization thermodynamics of several intermediate phases in the Pd–Yb system was investigated by means of vaporization experiments performed under Knudsen conditions (KEML, Knudsen Effusion Mass Loss). The following thermal decomposition processes were studied in the overall temperature range 819–1240 K and their enthalpy changes determined: 4 PdYb(s) = Pd4Yb3(s) + Yb(g); 5/3 Pd4Yb3(s) = 4/3 Pd5Yb3(s) + Yb(g); 21/13 Pd5Yb3(s) = 5/13 Pd21Yb10(s) + Yb(g); 1/3 Pd21Yb10(s) = 21/9 Pd3Yb(s) + Yb(g). Additional measurements were performed by KEMS (Knudsen Effusion Mass Spectrometry) on a Pd-rich two-phase sample, which allowed to detect both Yb(g) and Pd(g) in the vapor phase and to determine the atomization enthalpy of the Pd3Yb phase (Pd-rich composition boundary, Pd3.08Yb0.92): Pd3.08Yb0.92(s) = 0.92 Yb(g) + 3.08 Pd(g). The enthalpy of formation of this compound was thereafter determined as −68 ± 2 kJ/mol at. and, by combining this value with the decomposition enthalpies derived by KEML, the enthalpies of formation of the studied Pd–Yb intermediate phases were evaluated (kJ/mol at.): −75 ± 4 (Pd21Yb10), −75 ± 3 (Pd5Yb3), −73 ± 3 (Pd4Yb3), and −66 ± 3 (PdYb). A modified version of the Pd–Yb phase diagram is also reported, re-drawn on the basis of literature data and of new experimental information recently become available.

The title compounds have been synthesized and characterized both from the structural and magnetic point of view. Both crystallize in a new monoclinic structure strictly related to the tetragonal BaCd11 type. The structure was solved by means of X-ray single-crystal techniques for GdNi8Si3 and confirmed for TbNi8Si3 on powder data; the corresponding lattice parameters (obtained from Guinier powder patterns) are a=6.3259(2), b=13.7245(5), c=7.4949(3) A, β=113.522(3)°, Vcell=596.64(3) A3 and a=6.3200(2), b=13.6987(4), c=7.4923(2) A, β=113.494(2)°, Vcell=594.88(2) A3. The symmetry relationship between the tI48-I41/amd BaCd11 aristotype and the new ordered mS48-C2/c GdNi8Si3 derivative is described via the Barnighausen formalism within the group theory. The large Gd–Gd (Tb–Tb) distances, mediated via Ni–Si network, likely lead to weak magnetic interactions. Low-field magnetization vs temperature measurements indicate weak and field-sensitive antiferromagnetic ground state, with ordering temperatures of 3 K in GdNi8Si3 and about 2–3 K in TbNi8Si3. On the other hand, the isothermal field-dependent magnetization data show the presence of competing interactions in both compounds, with a field-induced ferromagnetic behavior for GdNi8Si3 and a ferrimagnetic-like behavior in TbNi8Si3 at the ordering temperature TC/N of about (or slightly higher than) 3K. The magnetocaloric effect, quantified in terms of isothermal magnetic entropy change ΔSm, has the maximum values of –19.8 J(kg K)−1 (at 4 K for 140 kOe field change) and −12.1 J(kg K)−1 (at 12 K for 140 kOe field change) in GdNi8Si3 and TbNi8Si3, respectively.

The Gd–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analyses. The existence of the known compounds, i.e.: GdNi10Si2, GdNi8Si3, GdNi5Si3, GdNi7Si6, GdNi6Si6, GdNi4Si, GdNi2Si2, GdNiSi3, Gd3Ni6Si2, GdNiSi, GdNiSi2, GdNi0.4Si1.6, Gd2Ni2.35Si0.65, Gd3NiSi2, Gd3NiSi3 and Gd6Ni1.67Si3, has been confirmed. Moreover, five new phases have been identified in this system. The crystal structure for four of them has been determined: Gd2Ni16−12.8Si1−4.2 (Th2Zn17-type), GdNi6.6Si6 (GdNi7Si6-type), Gd3Ni8Si (Y3Co8Si-type) and Gd3Ni11.5Si4.2 (Gd3Ru4Ga12-type). The compound with composition ~Gd2Ni4Si3 still remains with unknown structure. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi5, GdNi3, GdNi2, GdNi, GdSi2 and GdSi1.67; while no appreciable solubility was observed for the other binary compounds of the Gd–Ni–Si system. Magnetic properties of the GdNi6Si6, GdNi6.6Si6 and Gd3Ni11.5Si4.2 compounds have also been investigated and are here reported.

The phases reported in the literature as “R2Pd3” (R = rare earth element) have been reinvestigated. The exact stoichiometric composition of this series of compounds, which form for R = Sc, Y, and from Gd to Lu, including Yb, was found to be R3Pd5. All of them crystallize in the orthorhombic Pu3Pd5 structure type (oS32-Cmcm). The crystal structure has been refined from both single crystal (for Tb3Pd5) and powder X-ray diffraction data (for Tb3Pd5, Ho3Pd5, and Tm3Pd5). These compounds represent the first example of a binary phase formed by R and Pd adopting the Pu3Pd5-type featuring two crystallographic nonequivalent sites for the R atoms in the unit cell (the Wyckoff sites 4c and 8e). The variation of the lattice parameters and unit cell volume along the series strictly follows the trend of the lanthanide contraction. An extrapolation of the volume contraction versus the R3+ ionic radius gives an atomic volume of 29.74 A3 for Yb in the hypothetical trivalent metallic state (under normal conditions). The fo...

A crystallochemical study was undertaken to investigate the structural stability and the compositional extent of the ternary borides M2(Ni21−xMx)B6 (M Ti, Zr, Hf). This phase often occurs during the production of MB2 joints by means of Ni–B brazing alloys. Samples with the nominal compositions M2Ni21B6 and M3Ni20B6 were synthesized by arc melting and characterized by optical and electron microscopy, and X-ray diffraction. Crystal structure refinements were performed by the Rietveld method. The compositional boundaries of the ternary phases were experimentally determined and found strictly related to the M/Ni size ratio. The stability of this structure is mainly determined by the capability of the structure to expand under the effect of the Ni substitution by the M atom. The CALPHAD modeling of the three M–Ni–B ternary systems in the Ni-rich corner of the phase diagram, performed on the basis of the obtained structural data, shows a good agreement with experimental results.

The magnetic structure of the Fe 2 P-type R 6 CoTe 2 phases ( R =Gd–Er, space group P 6¯2 m ) has been investigated through magnetization measurement and neutron powder diffraction. All phases demonstrate high-temperature ferromagnetic and low-temperature transitions: T C =220 K and T CN =180 K for Gd 6 CoTe 2 , T C =174 K and T CN =52 K for Tb 6 CoTe 2 , T C =125 K and T CN =26 K for Dy 6 CoTe 2 , T CN =60 K and T N =22 K for Ho 6 CoTe 2 and T CN ∼30 K and T N ∼14 K for Er 6 CoTe 2 . Between 174 and 52 K Tb 6 CoTe 2 has a collinear magnetic structure with K 0 =[0, 0, 0] and with magnetic moments along the c -axis, whereas below 52 K it adopts a non-collinear ferromagnetic one. Below 60 K the magnetic structure of Ho 6 CoTe 2 is that of a non-collinear ferromagnet. The holmium magnetic components with a K 0 =[0, 0, 0] wave vector are aligned ferromagneticaly along the c -axis, whereas the magnetic component with a K 1 =[1/2, 1/2, 0] wave vector are arranged in the ab plane. The low-temperature magnetic transition at ∼22 K coincides with the reorientation of the Ho magnetic component with the K 0 vector from the collinear to the non-collinear state. Below 30 K Er 6 CoTe 2 shows an amplitude-modulate magnetic structure with a collinear arrangement of magnetic components with K 0 =[0, 0, 0] and K 1 =[1/2, 1/2, 0]. The low-temperature magnetic transition at ∼14 K corresponds to the variation in the magnitudes of the M Er K0 and M Er K1 magnetic components. In these phases, no local moment was detected on the cobalt site. The magnetic entropy of Gd 6 CoTe 2 increases from Δ S mag =−4.5 J/kg K at 220 K up to Δ S mag =−6.5 J/kg K at 180 K for the field change Δ μ 0 H =0–5 T.

We have grown a single crystal of HoAl2Ge2, which crystallizes in the hexagonal CaAl2Si2 type structure with Ho ions in the trigonal coordination in the ab plane. The data obtained from the bulk measurement techniques of magnetization, heat capacity and transport reveal that HoAl2Ge2 orders antiferromagnetically at TN ∼6.5 K. The susceptibility below TN and isothermal magnetization at 2 K indicate the ab plane as the easy plane of magnetization. Heat capacity data reveal a prominent Schottky anomaly with a broad peak centered around 25 K, suggesting a relatively low crystal electric field (CEF) splitting. The electrical resistivity reveals the occurrence of a superzone gap below TN. The point charge model of the CEF is applied to the magnetization and the heat capacity data. While a good fit to the paramagnetic susceptibility is obtained, the CEF parameters do not provide a satisfactory fit to the isothermal magnetization at 2 K and the Schottky anomaly.

Motivated by the report of superconductivity in R3TiSb5 (R = La and Ce) and possibly Nd3TiSb5 at ∼4 K, we grew single crystals of La3TiSb5 and Ce3TiSb5 by the high-temperature solution method using Sn as a flux. While in both compounds we observed a superconducting transition at 3.7 K for resistivity and low-field magnetization, our data conclusively show that it arose from residual Sn flux present in the single crystals. In particular, the heat capacity data do not present any of the anomalies expected from a bulk superconducting transition. The anisotropic magnetic properties of Ce3TiSb5, crystallizing in a hexagonal P63/mcm structure, were studied in detail. We find that the Ce ions in Ce3TiSb5 form a Kondo lattice and exhibited antiferromagnetic ordering at 5.5 K with a reduced moment and a moderately normalized Sommerfeld coefficient of 598 mJ/mol K2. The characteristic single-ion Kondo energy scale was found to be ∼8 K. The magnetization data were subjected to a crystal electric field (CEF) analysis. The experimentally observed Schottky peak in the 4f-electron heat capacity of Ce3TiSb5 was reproduced fairly well by the energy levels derived from the CEF analysis.

International audience; We compare, thanks to a Sagnac interferometer, the phase sensitivity to strain of different microstructured optical silica fibers (MSF) that we design and fabricate. Our results show that when a same elongation is applied to different MSF, the induced phase change is equal or lower than the one obtained for a standard fiber, showing no advantage on this parameter for sensing applications.

The magnetic structure of the ternary intermetallic compound Ho6FeTe2 (hexagonal Zr6CoAs2 structure type, a ternary ordered variant of the Fe2P-type; space group P 6 ¯ 2 m , No 189) has been investigated by neutron diffraction and magnetization measurements. The neutron diffraction study shows that in between the temperatures TN ∼ 24 K and TC ∼ 8 K the magnetic moments of the Ho atoms adopt a flat helix ordering with elliptical envelope having a wave vector K = [0, 0, ∼1/9], the helix axis being coincident with the c-axis (with maximal magnetic moments of M H o 1 = 6.5 ( 7 ) μ B and M H o 2 = 8.0 ( 7 ) μ B , at 10 K). Below the TC ∼ 8 K the magnetic structure of Ho6FeTe2 changes to a ferromagnetic cone: superposed on the helix ordering within the basal plane a ferromagnetic ordering with K = [0, 0, 0] and moments pointing in the c-direction appears. At 2 K the total maximal magnetic moments amount to M H o 1 = 9.1 ( 7 ) μ B and M H o 2 = 9.6 ( 7 ) μ B with a ferromagnetic component on the H o 1 site of M c H o 1 = 2.2 ( 5 ) μ B and on the H O 2 site of M c H o 2 = 5.2 ( 5 ) μ B . No local moment was detected on the iron atomic site in this compound. Magnetization measurements confirm the first magnetic transition at ∼26 K and the second at ∼10 K. The magnetization vs. field data obtained at 2.5 K show soft ferromagnetic behavior, with a saturation magnetization of 7.9 μB/Ho3+.

Magnetization and neutron diffraction studies have been performed on Pr4Sb3, Nd4Sb3, Sm4Sb3 and on the Nd2Pr2Sb3 solid solution (all cubic anti-Th3P4-type, Space group I over(4, ?) 3 d, N. 220). Magnetization data on Sm4Sb3 reveal a ferromagnetic transition at TC = 168 K. The neutron diffraction study indicates a spin-canted commensurate antiferromagnetic structure below TC = 37 K and 52 K for Pr4Sb3 and Pr2Nd2Sb3 compounds, respectively; for Nd4Sb3, on lowering the temperature first a ferromagnetic structure appears at TC = 77 K which is followed below TC2 = 39 K again by a spin-canted structure. At 2 K the magnetic moments amount to ?2.89 ?B/Pr3+, ?2.86 ?B/(Pr0.5Nd0.5)3+ and ?2.98 ?B/Nd3+, respectively for Pr4Sb3, Pr2Nd2Sb3 and Nd4Sb3. The magnetic propagation vector is in all cases ? = [0, 0, 0]. The canting increases when going from Nd4Sb3 over Nd2Pr2Sb3 to Pr4Sb3. � 2010 Elsevier B.V. All rights reserved.

We provide a complete experimental characterization of stimulated Brillouin scattering in a 160 m long solid-core photonic crystal fiber, including threshold and spectrum measurements as well as positionresolved mapping of the Brillouin frequency shift. In particular, a three-fold increase of the Brillouin threshold power is observed, in excellent agree-ment with the spectrally-broadened Brillouin gain spectrum. Distributed measurements additionally reveal that the rise of the Brillouin threshold results from the broadband nature of the gain spectrum all along the fiber and is strongly influenced by strain. Our experiments confirm that these unique fibers can be exploited for the passive control or the suppression of Brillouin scattering. © 2007 Optical Society of America.

special issue « Fiber Optic Research in France » (Part III of III); International audience; We present the important fabrication issues involved with the realization of low loss, low water peak, nonlinear holey fibers based on the Stack and Draw technique. We have realized fibers with loss performances in the 1.38 μm spectral region that are limited by the intrinsic losses of the raw materials, opening up the possibility of using long lengths of such fibers to demonstrate phenomenon such as Raman amplification and supercontinuum generation using continuous wave pump sources.

We study the generation of supercontinua in air–silica microstructured fibers by both nanosecond and femtosecond pulse excitation. In the nanosecond experiments, a 300-nm broadband visible continuum was generated in a 1.8-m length of fiber pumped at 532 nm by 0.8-ns pulses from a frequency-doubled passively Q-switched Nd:YAG microchip laser. At this wavelength, the dominant mode excited under the conditions of continuum generation is the LP11 mode, and, with nanosecond pumping, self-phase modulation is negligible and the continuum generation is dominated by the interplay of Raman and parametric effects. The spectral extent of the continuum is well explained by calculations of the parametric gain curves for four-wave mixing about the zero-dispersion wavelength of the LP11 mode. In the femtosecond experiments, an 800-nm broadband visible and near-infrared continuum has been generated in a 1-m length of fiber pumped at 780 nm by 100-fs pulses from a Kerr-lens model-locked Ti:sapphire laser. At this wavelength, excitation and continuum generation occur in the LP01 mode, and the spectral width of the observed continuum is shown to be consistent with the phase-matching bandwidth for parametric processes calculated for this fiber mode. In addition, numerical simulations based on an extended nonlinear Schrodinger equation were used to model supercontinuum generation in the femtosecond regime, with the simulation results reproducing the major features of the experimentally observed spectrum.

International audience; Neutron powder diffraction experiments have been carried out on the well-known NaCl-type polycrystalline NdSb compound. The neutron diffraction data obtained in zero field at 2 K, reveal commensurate antiferromagnetic ordering with magnetic moments of Nd directed along Z axis (M(Nd) = 3.1(1) mu(B)). Thermal variation of intensity of (001) magnetic reflection shows the temperature of magnetic ordering at T(N) = 13 K.

session We3.P « posters » [We3.P.12], ISBN 2-912328-34-9; International audience; We report 570-fs pulse generation based on soliton-effect compression in a 22 m-long non-linear holey fibre. Using soliton-effect compression, we propose a simple method to measure second-order dispersion of fibres in the anomalous dispersion regime.