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The equiatomic ternary compounds NdMnAl and RMnIn (R=Nd, Gd, Dy, Er, and Y) have been synthesized for the first time. In this paper, we report their crystal structure and the magnetic behavior of three of them (i.e., NdMnAl, GdMnIn, and DyMnIn). While NdMnAl and NdMnIn have the cubic, Laves-phase, C-15-type structure, the latter compounds form in the closely related hexagonal, Laves-phase, C-14-type structure. The Mn ions carry a substantial magnetic moment in the three compounds, but magnetization does not exhibit signatures of long-range magnetic ordering. Broad peaks in the thermal variation of magnetization, accompanied with thermomagnetic irreversibility below the peak region and hysteresis loops at low temperatures with large coercivity indicate spin glass-type freezing of the magnetic moments. The heat capacity data, measured in the range of 1.8 to 100 K, do not exhibit peaks associated with long-range magnetic order and, thus, corroborate the results inferred from magnetization data. Resistivities of these compounds are large and show negative temperature coefficients. These observations can be reconciled to a highly disordered state brought about by the random substitution of In or Al for Mn in these compounds.

Local structure of SmFe$_{1-x}$Ru$_x$AsO$_{0.85}$F$_{0.15}$ ($x$ = 0.0, 0.05, 0.25 and 0.5) superconductors has been investigated by temperature dependent As $K$-edge extended x-ray absorption fine structure. The effect of Ru substitution remains confined to the iron-arsenide layer but neither the static disorder nor the Fe-As bond strength suffers any change for $x \le$ 0.25. With further Ru substitution the static disorder increases while the Fe-As bond strength remains unchanged. Also, the Ru-As distance ($\sim$2.42 \AA), different from the Fe-As distance ($\sim$2.39 \AA), does not show any change in its force constant with the Ru substitution. These observations suggest that the SmFe$_{1-x}$Ru$_x$AsO$_{0.85}$F$_{0.15}$ system breaks down to coexisting local electronic phases on isoelectric substitution in the active FeAs layer.

The phase diagram of the ScIn system has been revised in the range 30 to 100 at.% In using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. Six intermediate phases have been found. Three of them have been confirmed: ScIn 3 (AuCu 3 -type). Sc 2 In (Ni 2 In-type) and Sc 3 In (Ni 3 Sn-type), while Sc 3 In 5 and Sc 5 In 3 should be replaced by ScIn 2 (ZrGa 2 -type) and ScIn respectively. The latter shows, however, a rather complex behaviour, assuming the CsCl- or AuCu-type structure, depending on composition. Tm 5 In 4 and Lu 8 In 4 (Ti 5 Ga 4 -type). LuIn (AuCu-type), Tm 3 In 4 and Lu 3 In 5 (Tm 3 Ga 5 -type) and LuIn 2 (ZrGa 2 -type), previously unknown, have also been prepared and characterized for comparison.

The R 2 Li 2 Si 3 compounds, with R = La, Ce, Pr, Nd and Sm, synthesized and structurally studied by powder and single crystal X-ray diffraction, belong to the Ce 2 Li 2 Ge 3 orthorhombic type. The magnetization and heat capacity data show the occurrence of normally trivalent cerium ions in Ce 2 Li 2 Si 3 ordering ferromagnetically at 17 K. Pr 2 Li 2 Si 3 becomes antiferromagnetic at 18 K, its isothermal magnetisation at 1.8 K showing a field induced spin flip transition at 25 kOe. For Nd 2 Li 2 Si 3 the transition to the antiferromagnetic state occurs at 9.5 K. Two peaks are seen in the heat capacity data of Ce 2 Li 2 Si 3 and Nd 2 Li 2 Si 3 which can be attributed to either two symmetry inequivalent rare earth sublattices ordering at different temperatures or to spin re-orientation.

We measured the 27Al and 11B NMR spin lattice relaxation rates and the isotropic Knight shifts in powder samples of Mg1−xAlxB2, as a function of the Al concentration, x. The temperature independence of the Knight shifts and the linear temperature dependence of the relaxation are verified throughout the compositions explored. The variation with x of the measured quantities is discussed in terms of the projected densities of states at the Fermi energy, finding good qualitative as well as quantitative agreement with recent band structure calculations.

We present resistivity and thermal conductivity measurements on bulk samples, prepared either by a standard method or by a one-step technique. The latter samples, due to their high density and purity, show residual resistivity values as low as 0.5 mW cm and thermal conductivity values as high as 215 W/mK, higher than the single crystal ones. Thermal and electrical data of all the samples are analysed in the framework of the Bloch-Gruneisen equation giving reliable parameter values. In particular the temperature resitivity coefficient, obtained both from resistivity and thermal conductivity, in the dirty sample comes out ten time larger than in the clean ones. This result supports the hypothesis of ref. [1] that p and s bands conduct in parallel, prevailing p conduction in clean samples and s conduction in dirty samples ., Comment: 8 pages, 5 figures, Presented at the BOROMAG workshop, June 17-19 2002, Genoa, Italy

The defective structure of the PrFe0.4Sn2 and ThFe0.2Sn2 compounds has been studied by 57 Fe and 119 Sn Mossbauer spectro- scopy, first-principle and binomial distribution calculations. It is shown that the iron and tin sites display different local interactions of atoms located in the same structural position of the defective structure. The analysis of the obtained data together with the theoretical calculations show that defect formation in the samples has a thermal origin. The experimental and theoretical data show that the studied defective structure is locally ordered. # 2002 Elsevier Science Ltd. All rights reserved.

We present a systematic characterization of Mg1−xLixB2 polycrystalline samples with nominal Li content x up to 0.30. We explore the effectiveness of the substitution and investigate its influence on superconducting and normal state properties. The structural analyses by neutron and x-ray diffraction indicate that, despite the lattice parameters remaining unchanged within the experimental accuracy, around 30% of the nominal Li content actually enters the structure. Also the transition temperature is only weakly affected by Li substitution, but its relationship with the residual resistivity and magnetoresistivity data is compatible with a picture where π bands are filled with holes and/or affected by disorder, as predicted by theory. We also measured the magnetic penetration depth λ by an inductance technique. Data fits based on the standard Bardeen–Cooper–Schrieffer two-band model yield the zero-temperature limit of both λ and superconducting gaps: we find that λ(0) increases weakly and quickly saturates with increasing x, whereas Δπ(0) and Δσ(0) decrease with x. This analysis suggests that lithium substitution induces disorder mainly in the π band. Point contact spectroscopy results on samples obtained from the same batch are in full agreement with magnetic penetration depth data on the undoped sample, but give superconducting gaps almost insensitive to Li substitution, showing at most a small increase in Δπ(0) that may be related to an inhomogeneous distribution of Li content.

Powdered and sintered MgB2 samples have been characterized through magnetic measurements performed from T = 5 K up to few degrees above the transition temperature of about 39 K. We found that the sintered samples behave as well-connected bodies, showing no trace of granularity. In order to obtain the critical current density value Jc the Critical State Model has been therefore employed in a straightforward way. With the aim either to decrease the electron mean free path or to increase its Jc we have attempted to introduce defects in the MgB2 structure by different procedures: substitution of Lithium on the Magnesium site and doping of the precursor Boron powders with Aluminum and Silicon. The best result in terms of Jc has been achieved by Silicon doping that, moreover, does not significantly affect the transition temperature., Comment: 10 pages, 6 figures, 1 table

We have investigated the structural and magnetic properties of RCu 9 Sn 4 and RCu 9.4 Sn 3.6 (R=La to Nd) compounds. Besides the earlier reported RCu 9.4 Sn 3.6 phases for which we confirm the NaZn 13 -type cubic structure, our studies reveal the existence of the new intermetallic compounds RCu 9 Sn 4 , crystallising in the LaFe 9 Si 4 -type tetragonal structure. Synthesis by arc-melting is preferable to induction melting to produce single phase samples of these compounds. Although the two series of compounds do not differ in the overall composition, the change of structure affects the magnetic properties appreciably. While the RCu 9 Sn 4 compounds, with R=Ce, Pr and Nd, order ferromagnetically at 5.5, 10.5 and 15 K, respectively, the corresponding RCu 9.4 Sn 3.6 do not order above 1.5 K with the exception of NdCu 9.4 Sn 3.6 which shows a magnetic transition near 2 K.

The phase diagram of the Ca–Sn system has been investigated in the whole composition range using differential thermal analysis, metallographic analysis, single-crystal and powder X-ray diffraction. Seven intermediate phases have been found. Four of them have been confirmed: CaSn 3 (AuCu 3 -type), CaSn (CrB-type), Ca 31 Sn 20 (Pu 31 Rh 20 -type) and Ca 2 Sn (Co 2 Si-type); while Ca 7 Sn 6 (Ca 7 Sn 6 -type), Ca 36 Sn 23 (Yb 36 Sn 23 -type) and Ca 5 Sn 3 (Cr 5 B 3 -type) have been identified and characterized for the first time. Four eutectic points occur in this system: at about 5 at.% Sn and 780°C, 48 at.% Sn and 995°C, 68 at.% Sn and 610°C, and at less than 1 at.% Ca and 225°C.

The phase diagram of the Ca-Si system has been investigated across almost the whole composition range (0 to 70 at% Si) using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. Six intermediate phases have been found: CaSi2 (CaSi2-type), Ca14Si19 (Ca14Si19-type), Ca3Si4 (Ca3Si4-type), CaSi (CrB-type), Ca5Si3 (Cr5B3-type) and Ca2Si (anti-PbCl2-type). Ca3Si4, not previously known, is a Zintl phase representative of a new structural type: hexagonal hP42, a=854.1, c=1490.6 pm, space group P6 3 /m. Three eutectics occur in this system: at about 3.5 at% Si and 795°C, 42.5 at% Si and 1230°C, 72.0 at% Si and 1020°C.

Thermodynamic, magnetic and electrical properties of the Nd 7 Co 6 Al 7 intermetallic phase have been extensively studied. The compound crystallises in the tetragonal Pr 7 Co 6 Al 7 type structure (space group P4/mbm) and undergoes a ferromagnetic transition at 15.5 K. From the hysteresis loop the values of the remanence and of the coercive field were obtained. Magnetic heat capacity measurements allow to obtain the magnetocaloric effect related to the magnetic transition. An estimate of refrigerant capacity of the compound is obtained.

R 3 Cu 4 Sn 4 (R=rare earth) compounds crystallise in the orthorhombic, Gd 3 Cu 4 Ge 4 -type structure with space group Immm . There are two inequivalent crystallographic sites for the rare earth ions in this structure. We have studied the magnetic properties of compounds with R=Ce, Gd and Y, respectively. Both the symmetry inequivalent Ce-ions are found to be in the trivalent state. Multiple magnetic transitions are observed in Ce 3 Cu 4 Sn 4 and Gd 3 Cu 4 Sn 4 with comparable highest transition temperature (∼10.4 and ∼13 K, respectively), which is incompatible with the de Gennes scaling. There is no signature of Kondo effect in Ce 3 Cu 4 Sn 4 . Y 3 Cu 4 Sn 4 is a Pauli paramagnet.

We report the synthesis and some physical properties of four Th-based compounds ThCoGe, ThNiGe, ThCuAl3 and ThNiAl3. These compounds, are to our knowledge, being reported here for the first time. We observe Pauli paramagnetic behaviour in all the four compounds (with possible exception of ThCoGe), which shows that the 3d-derived electronic bands are filled by charge transfer. No signature of superconductivity is observed down to 1.4 K in these materials.

The phase diagram of the Ba-Ge system has been revised, in the composition range 0-75 at.% Ge, from a thermal point of view, resulting substantially different from that previously reported in Massalski collection. The existence and composition of the following compounds are confirmed: Ba2Ge, Ba5Ge3, BaGe, dimorphic Ba3Ge4, BaGC2, Ba6Ge25 and Ba8Ge43. Save for Ba2Ge, BaGe and BaGe2, forming congruently, all other phases melt incongruently. Four eutectic points occur at 7.5, 42.5, 56.0 and 82.5 at.% Ge, respectively. (c) 2007 Elsevier B.V. All rights reserved.

The phase diagram of the Eu–Sn system has been investigated in the whole composition range using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. Five intermediate phases have been found. Two of them have been confirmed: EuSn 3 (AuCu 3 -type) and EuSn (CrB-type); while Eu 3 Sn 5 (Pu 3 Pd 5 -type), Eu 5 Sn 3 (W 5 Si 3 -type) and Eu 2 Sn (Co 2 Si-type) have been prepared and characterized for the first time. Four eutectic points occur in this system: at 5 at % Sn and 790°C, 44 at % Sn and 1075°C, 74 at % Sn and 785°C and at less than 1 at % Eu and 230°C.

The phase diagrams of the ScSn and ScPb systems have been investigated using differential thermal analysis (DTA), metallographic analysis, X-ray diffraction (XRD) and electron microscopy. The Sc-rich side of both systems (0–30 at.% Sn or Pb) has not been studied owing to the high melting temperatures of the corresponding alloys and contamination of the samples by the container material (Mo). The two systems are very similar to one another; with tin, however, two more intermediate phases are formed. Sc5X3 and Sc6X5 compounds are isomorphous, Mn5Si3 and Ti6Ge5 types respectively. ScSn2 is a new intermetallic compound with a new structure type. The impossibility of finding single crystals for XRD prevented the determination of the structure and then of the exact stoichiometry for ScSn which was assigned taking into account the results of DTA, XRD, optical and electronic microanalysis. Sc5X3, different from the other intermediate phases, shows appreciable solid solution range towards compositions richer in X.

The phase diagram of the USn system has been investigated using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. The U-rich side of the system (0–15 at.%Sn) has not been studied owing to the high reactivity and contamination of the samples by the container material (Mo). Five intermediate phases have been found, four of which not previously known: U 5 Sn 4 (Ti 5 Ga 4 -type), USn (ThIn-type), USn 2 (ZrGa 2 -type), U 3 Sn 7 (Ce 3 Sn 7 -type) and USn 3 (AuCu 3 -type). The main feature of the USn phase diagram is that the relevant temperatures are confined in a narrow range of about 50° (1340–1390 °C) giving rise to some difficulties in determining the melting behaviour of the compounds and in drawing the shape of the diagram. Another singular behaviour has been observed for the mean atomic volumes along the whole system.

The intermetallic compounds Yb 2 Ge, Eu 2 Ge and Eu 2 Si were synthesized from the elements by HF melting in tantalum crucibles. The three phases crystallize in the PbCl 2 structure type, as shown by Rietveld refinement of powder pattern intensity data. The structure of Yb 2 Ge was confirmed by a single crystal study.

A novel method to prepare bulk Fe(Se0.5Te0.5) samples is presented, based on a melting process and a subsequent annealing treatment. With respect to the standard sintering technique, it produces much more homogeneous and denser samples, characterized by large and well interconnected grains. The resulting samples exhibit optimal critical temperature values, sharp resistive and magnetic transitions, large magnetic hysteresis loops and high upper critical fields are observed. Interestingly, the global critical current density is much enhanced as compared to the values reported in literature for bulk samples of the same 11 family, reaching about 103 A/cm2 at zero field at 4.2 K as assessed by magnetic, transport and magneto-optical techniques. Even more importantly, its field dependence turns out to be very weak, such that at \mu_{0}H = 7 T it is suppressed only by a factor \sim2., Comment: 21 pages, 15 figures

The synthesis and structural characterization of phases in the R–Li–Ge (R = rare earth) systems are reported. The R4LiGe4 compounds with R = La–Nd, Sm complete the series, where the analogues with R = Gd–Tm, Lu were confirmed, all crystallizing with the Tm4LiGe4 type. Nd4LiGe4 and Ho4LiGe4 were structurally studied by single crystal X-ray diffraction (space group Pnma, Z = 4, Pearson code oP36). Nd4LiGe4: a = 7.367 (1) A, b = 15.116 (5) A, c = 7.947 (3) A, wR2 = 0.054; Ho4LiGe4: a = 7.077 (4) A, b = 14.585 (6) A, c = 7.670 (3) A, wR2 = 0.067. The phase Pr7Li8Ge10 crystallizes with a novel orthorhombic structure (space group Cmmm, Z = 2, Pearson code oS50): a = 6.8945 (7) A, b = 33.531 (6) A, c = 4.4400 (2) A, wR2 = 0.060. Isotypic compounds were found also with R = La, Ce, Nd. A third series R3Li4Ge4 with R = La–Nd, Sm crystallizes with the Gd3Cu4Ge4 type. The structure was refined for the Nd analogue with the final composition Nd3Li3.65(2)Ge4.35(2) (space group Immm, Z = 2, Pearson code oI22): a = 4.3935 (5) A, b = 6.811 (1) A, c = 14.619 (3) A, wR2 = 0.068. The Pr7Li8Ge10 structure is closely related to both Ce2Li2Ge3 and Gd3Cu4Ge4 types. They belong to a structural series with general formula R2m+nM4mX2m+2n formed by m and n segments of the MgCuAl2 and AlB2 types, respectively. All the examined structures are characterized by the trigonal prismatic coordination around the germanium atoms, which represents a common feature of the R–Li–Ge compounds.

We investigate the effect of external pressure on magnetic order in undoped LnFeAsO (Ln = La, Ce, Pr, La) by using muon-spin relaxation measurements and ab-initio calculations. Both magnetic transition temperature $T_m$ and Fe magnetic moment decrease with external pressure. The effect is observed to be lanthanide dependent with the strongest response for Ln = La and the weakest for Ln = Sm. The trend is qualitatively in agreement with our DFT calculations. The same calculations allow us to assign a value of 0.68(2) $\mu_B$ to the Fe moment, obtained from an accurate determination of the muon sites. Our data further show that the magnetic lanthanide order transitions do not follow the simple trend of Fe, possibly as a consequence of the different $f$-electron overlap., Comment: 16 pages, 11 figures

The phase diagram of the Ce-Rh system (0–70 at.% Rh) was investigated using differential thermal analysis, micrographic analysis, X-ray diffraction and electron microscopy. Seven compounds are formed in this system. Their existence was already known and has been confirmed in the present investigation. Ce 4 Rh 3 and β-Ce 5 Rh 3 previously reported have been deleted. The shape of the diagram is very different from that reported in the current literature, with melting points in the 20–60 at.% Rh range being lower by several hundreds of degrees Celsius. The rhodium-rich side of the system could not be investigated due to the reaction of the alloys with the container material at temperatures higher than 1350 °C.

A new family of the noble metal-actinide intermetallics was investigated. The electrical resistivity and magnetic susceptibility measurements on some pseudobinary phases in the U 14 Au 51 Th 14 Au 51 system are reported. The effects of the observed competition between strong antiferromagnetic coupling and itinerant. Kondo-like 5f states are discussed.

Superconducting epitaxial FeSe0.5Te0.5 thin films were prepared on SrTiO3 (001) substrates by pulsed laser deposition. The high purity of the phase, the quality of the growth and the epitaxy were studied with different experimental techniques: X-rays diffraction, reflection high energy electron diffraction, scanning tunnelling microscopy and atomic force microscopy. The substrate temperature during the deposition was found to be the main parameter governing sample morphology and superconducting critical temperature. Films obtained in the optimal conditions show an epitaxial growth with c axis perpendicular to the film surface and the a and b axis parallel to the substrates one, without the evidence of any other orientation. Moreover, such films show a metallic behavior over the whole measured temperature range and critical temperature above 17K, which is higher than the target one., 10 pages including 4 figures

The synthesis and crystal structure of the new family of rare earth ternary equiatomic RZnGe phases are reported. The compounds are found to form for R = La to Nd, Sm, Gd to Tm, Y, all crystallizing with the hexagonal hP12-P63/mmc YPtAs structure type, a four-layers superstructure derivative of the AlB2 type. No formation of the equiatomic phase has been observed for R = Lu and Sc. The unit cell parameters, as obtained by the Guinier method on polycrystalline samples, vary regularly from the La [a = 4.333(1), c = 17.017(2) A] to the Tm homologous [a = 4.192(1), c = 15.314(2) A]. The crystal structure has been refined for the Ce, Gd and Y compounds by single crystal data.

Less than two years after the discovery of high temperature superconductivity in oxypnictide LaFeAs(O, F) several families of superconductors based on Fe layers (1111, 122, 11, 111) are available. They share several characteristics with cuprate superconductors that compromise easy applications, such as the layered structure, the small coherence length and unconventional pairing. On the other hand, the Fe-based superconductors have metallic parent compounds and their electronic anisotropy is generally smaller and does not strongly depend on the level of doping, and the supposed order parameter symmetry is s-wave, thus in principle not so detrimental to current transmission across grain boundaries. From the application point of view, the main efforts are still devoted to investigate the superconducting properties, to distinguish intrinsic from extrinsic behaviors and to compare the different families in order to identify which one is the fittest for the quest for better and more practical superconductors. The 1111 family shows the highest Tc, huge but also the most anisotropic upper critical field and in-field, fan-shaped resistive transitions reminiscent of those of cuprates. On the other hand, the 122 family is much less anisotropic with sharper resistive transitions as in low temperature superconductors, but with about half the Tc of the 1111 compounds. An overview of the main superconducting properties relevant to applications will be presented. Upper critical field, electronic anisotropy parameter, and intragranular and intergranular critical current density will be discussed and compared, where possible, across the Fe-based superconductor families.

We studied the effects of co-doping with Li and Al on the energy gaps of MgB2 by performing point-contact Andreev-reflection spectroscopy (PCAR) in polycrystalline Mg1−x(AlαLi1−α)xB2 samples with x≤0.4. Even though the lattice parameters and the critical temperature of the compound simply scale with the effective Al content αx, irrespective of the Li concentration, the energy gaps do not. In particular, for a given effective Al content, the comparison with Mg1−y(Al)yB2 with y = αx shows that the σ bandgap is practically the same while the π bandgap is higher. A clear gap merging is observed in the most doped sample (x = 0.4) when Tc

We report measurements of resistivity, magnetoresistivity, Hall effect, Seebeck coefficient, infrared reflectivity of undoped SmFeAsO and lightly doped SmFeAs(O0.93F0.07) oxypnictides. All the properties measured on SmFeAsO are characterized by clear signatures of the magnetic instability. A self-consistent picture emerges in which below the magnetic transition carrier condensation occurs due to the opening of spin density wave (SDW) gap. This is accompanied by the mobility increase of not gapped carriers due to the suppression of electron-electron scattering. SmFeAs(O0.93F0.07) exhibits an increase of the metallic character on cooling consistent with electron doping, even though at room temperature values of all the properties nearly overlaps with those of SmFeAsO. However, with temperature decrease all anomalies related to the SDW instability are missed and the superconducting transition occurs. This suggests that doping breaks abruptly the symmetries of the Fermi surface inhibiting the SDW formation in favor of the superconducting transition, with no substantial changes in the density of states or in the effective mass., Comment: Submitted to SUST

The phase diagram of the Ce-Ru system has been investigated using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. The rutheniumrich side (75–100 at % Ru) has not been studied owing to the high melting temperature. The compounds Ce 7 Ru 3 (Th 7 Fe 3 type) and CeRu 2 (MgCo 2 type) have been confirmed; Ce 3 Ru not previously known was found to crystallize with the Fe 3 C structure type. Moreover, two new intermetallics have been found, i.e. Ce 16 Ru 9 and Ce 4 Ru 3 which are new structure types. None of these phases exhibits appreciable ranges of solid solubility. Additions of ruthenium do not significantly affect the transition temperature of cerium. The Ce-Ru phase diagram is rather different from those of the neighbouring rare earths lanthanum and neodymium, indicating once more an anomalous behaviour for cerium.

The phase diagram of the Lu–In system has been investigated in the range 25–100 at.% In, using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. Seven intermediate phases have been found: LuIn 3 (AuCu 3 type), LuIn 2 (ZrGa 2 type), Lu 3 In 5 (Tm 3 Ga 5 type), LuIn (AuCu type), Lu 5 In 4 (Ti 5 Ga 4 type), Lu 5 In 3 (Mn 5 Si 3 type) and Lu 2 In (Ni 2 In type). Some of them were already known, while the existence of new phases recently discovered has been confirmed. Lu 5 In 3 and Lu 5 In 4 give rise to a continuous solid solution range as they occur in the Zr–Sn system between Zr 5 Sn 3 and Zr 5 Sn 4 . At least three eutectics occur at about 23 at.% In and 1185°C, 58 at.% In and 960°C, less than 1 at.% In and 156°C.

The crystal structure of SmFeAsO has been investigated by means of Rietveld refinement of high resolution synchrotron powder diffraction data collected at 300 K and 100 K. The compound crystallizes in the tetragonal P4/nmm space group at 300 K and in the orthorhombic Cmma space group at 100 K; attempts to refine the low temperature data in the monoclinic P112/n space group diverged. On the basis of both resistive and magnetic analyses the tetragonal to orthorhombic phase transition can be located at T about 140 K., Submitted to: Superconductor Science and Technology PACS: 61.05.cp, 61.66.Fn, 74.10.+v, 74.62.Dh, 74.70.Dd

In this communication we present a transmission electron microscopy study on neutron-irradiated bulk samples. We give clear evidence that neutron irradiation creates nanometric amorphous regions within the crystal lattice. The density of these defects correctly scales with the neutron dose. These defects, whose size matches with the coherence length, act as pinning centers and are responsible for the strong increase of the critical current density at high field and for shifting the maxima of the pinning force curves toward higher fields.

Subsequent magnetic transitions were recently reported for the CeScSi-type RScGe (R = rare earth) equiatomic intermetallic compounds. The compounds TbScGe and NdScGe order ferromagnetically at TC = 216 K and TC = 200 K, respectively whereas PrScGe orders antiferromagnetically at TN = 140 K. In addition, PrScGe demonstrates two other magnetic transitions at TC1 = 88 K and TC2 = 80 K in an applied field of 5 kOe. An investigation by neutron diffraction has been now carried out on these phases in an attempt to solve the magnetic structures corresponding to each ordering, and in this article the results obtained are reported. Below the Curie point, the magnetic structure of TbScGe and NdScGe is collinear ferromagnetic. The magnetic moment of Tb atoms coincides with the Z-axis of CeScSi-type unit cell (MTb = 8.63μB at 2 K), whereas the magnetic moment of Nd atoms has the θ = 52(2)° angle with Z-axis (MNd = 3.53(2)μB at 2 K). Below the Neel temperature, TN = 140 K the magnetic structure of PrScGe consists of antiferromagnetic (0 0 2) rare-earth double layers with magnetic moments of the rare earth atoms collinearly ordered. The magnetic moments of Pr atoms (MPr = 1.72(3)μB at 100 K) have the θ = 62(2)° angle with the Z-axis. Between TC1 = 82 K and TC2 = 62 K the conversion of the commensurate antiferromagnetic collinear type structure to the ferrimagnetic collinear type structure with propagation vector K = [0, 0, 1/2] was observed: the magnetic moments of Pr double layers became sine modulated along the Z-axis. Below TC2 = 62 K the magnetic structure of PrScGe compound consists of ferrimagnetic (0 0 1/2) layers (amplitude of Pr magnetic moment MPr = 3.31(9)μB at 5 K).

"The high temperature decomposition of the intermediate phases of the Ba-Si system (namely, Ba2Si, Ba5Si3, BaSi, Ba3Si4 and BaSi2) was investigated by means of Knudsen effusion-mass spectrometry and Knudsen effusion-weight loss techniques. All barium silicides decompose at high temperature by losing monatomic gaseous barium. The standard enthalpy changes of the decomposition reactions were derived from vapor pressure measurements by the second- and third-law methods of analysis. From these values the heats of formation of all the barium silicides were calculated. First principles electronic structure calculations for the same compounds were also performed by the density functional theory approach, in the generalized gradient approximation, using plane wave basis functions and Vanderbilt ultrasoft pseudopotentials. The experimental ground state lattices of the barium silicides have been studied: structures have been relaxed and total energy values derived. These were used in combination with calculated total energies of diamond-silicon and fcc-barium to derive the heats of formation of the barium silicides. First principles predictions and experimental heats of formation are in satisfactory agreement. The selected values of the heats of formation of the intermediate phases of the Ba-Si system are (kJ mol-at.(-1)): Ba2Si, -35.8 +/- 7.0; Ba5Si3, -42.4 +/- 5.2; BaSi, -50.1 +/- 2.9; Ba3Si4, -50.7 +/- 3.1; and BaSi2, -46.7 +/- 3.5. (C) 2008 Elsevier Ltd. All rights reserved."