Curie-Weiss Paramagnetism Research Articles

Gadolinium spin dilution in the ferromagnetic solid solutions Gd2–x Y x Cu2Mg

Abstract Samples of the solid solution Gd2–x Y x Cu2Mg (in steps of x = 0.2) were synthesized from the elements in sealed tantalum ampoules in a high-frequency furnace. The polycrystalline samples were characterized by X-ray powder diffraction. The structure of Gd0.988(6)Y1.012(6)Cu2Mg was refined from single-crystal X-ray diffractometer data: Mo2B2Fe type, P4/mbm, a = 762.83(4), c = 375.48(2) pm, wR2 = 0.0277, 285 F 2 values and 13 variables. Single-crystal data gave no hint for Gd/Y ordering. All samples behave like Curie-Weiss paramagnets with stable trivalent gadolinium and ferromagnetic ordering at low temperature. Within the solid solution the Curie temperature drops almost linearly from T C = 113.5(1) K for Gd2Cu2Mg to 9.3(1) K for Gd0.2Y1.8Cu2Mg, allowing a precise adjustment of the magnetic ordering temperature through gadolinium spin dilution.

High-field magnetic and magnetocaloric properties of pseudo-binary Er1−xHoxNi2 (x = 0.25–0.75) solid solutions

Hydrogen is quickly becoming a desired type of fuel, however, the energy and cost required for liquefaction using today’s cooling technology is excessively high. Magnetic cooling based on the magnetocaloric effect is an energy-efficient and environmentally friendly alternative to commonly used vapor compression, but improvements in refrigerants are crucial for this technology to succeed. Polycrystalline Er1−xHoxNi2 (x = 0.25, 0.5, 0.75) Laves-phase solid solutions obtained by the arc-melting method have been investigated due to their potential for low-temperature refrigerants. Er0.75Ho0.25Ni2 and Er0.5Ho0.5Ni2 crystallize in cubic Laves phase superstructure (space group F-43 m), while Er0.25Ho0.75Ni2, similarly to the initial ErNi2 and HoNi2 binary compounds, crystallizes with the formation of the regular cubic C15 structure (space group Fd-3 m). To evaluate how the structure affects magnetic and magnetocaloric properties, studies in a wide magnetic field range, up to 14 T, were conducted. Measurements show all samples obey the second-order magnetic phase transition from ferromagnetic to paramagnetic state, and their Curie temperatures increase with increasing Ho content from 8 K for Er0.75Ho0.25Ni2 to 12.3 K for Er0.25Ho0.75Ni2. At higher temperatures, all solid solutions are Curie-Weiss paramagnets. However, it has been observed that the formation of the superstructure with lower translational symmetry seems to affect magnetic moments and magnetic entropy values. Er0.25Ho0.75Ni2, with the regular cubic C15 structure, showed the highest entropy changes of 43.5 J/kgK around 12 K, while Er0.75Ho0.25Ni2 and Er0.5Ho0.5Ni2, with cubic superstructure, provided ∼30 % lower results of 30.3 and 35.1 J/kgK, around 8 and 10 K, respectively, for magnetic field change of 14 T. Nevertheless, relatively large and reversible values of magnetic entropy prove that these compounds can be promising candidates for magnetic cooling operating within the low-temperature range needed for hydrogen liquefaction.

Ternary Laves phases with the MgCu4Sn-type structure: RECo4Mg (RE = Gd, Dy–Tm, Lu), EuNi4Mg and RET 4Cd (RE = Y, La–Nd, Sm, Gd–Dy; T = Cu, Pt)

Abstract Twenty five new ternary Laves phases RET 4Mg and RET 4Cd (RE = rare earth element; T = Co, Ni, Cu, Pt) have been synthesized from the elements using niobium or tantalum tubes as inert crucible materials. The lattice parameters have been derived from powder X-ray diffraction data. The structures of Ce1.41(1)Co4Mg0.59(1), Dy1.10(1)Co4Mg0.90(1), LaPt4Cd, Y1.10(1)Cu4Cd0.90(1), Ca0.93(1)Cd0.07(1)Pd2 and Eu0.87(2)Cd0.13(2)Pd2 were refined from single-crystal X-ray diffractometer data. Most phases show certain degrees of RE/Mg or RE/Cd disorder. The quenched phases are assigned to the MgCu2 structure, while the annealed ones adopt the MgCu4Sn type, a translationengleiche superstructure variant of the aristotype. The annealing time has a substantial influence on the degree of ordering and is expressed in the lattice parameters, i.e. larger ones for the disordered samples. The REPt4Cd (RE = La–Nd) samples have been characterized with respect to their magnetic properties. LaPt4Cd is a diamagnet, while CePt4Cd (2.23(1) µB), PrPt4Cd (3.40(1) µB) and NdPt4Cd (3.43(1) µB) are Curie–Weiss paramagnets. The cerium compound shows a slight moment reduction. NdPt4Cd is ordered ferromagnetically at T C = 4.4(1) K.

Synthesis and characterization of a new ordered rhombohedral pyrochlore family Ln3Sb3Cu2O14 (Ln=Pr,Nd, Sm, Eu, Tb, Dy) with more detailed study of the Sm compound

New polycrystalline compound with a rhombohedral pyrochlore structure and chemical formula Sm3Sb3Cu2O14 was synthesized in air by solid-state reaction method. The compound crystallizes in the rhombohedral system, with R-3m space group and Z = 3. Lattice parameters are a = 7.41681(2) Å and c = 17.24845(5) Å. The electrical resistivity, measured by impedance spectroscopy, highlights a semiconductor behavior with an activation energy Ea = 0.47 eV. The dielectric properties show a regular decrease of permittivity with temperature, the dielectric loss decreases at low temperature and remain stable around 0.8 at high temperature. Using UV–vis Diffuse Reflectance, we can assume that the band gap is around 3.28 eV. The magnetic susceptibility of Sm3Sb3Cu2O14, measured from 5 K to 800 K, shows Curie-Weiss paramagnetism behavior with a significant Van Vleck contribution from the Sm+3 magnetic cation.

Growth, structural characterization, DFT study, and magnetic properties of the NdAuIn crystal

A crystal of NdAuIn was successfully grown using the optical floating zone technique. Single-crystal and powder XRD studies confirmed that NdAuIn adopts a hexagonal ZrNiAl-type structure. Comparative analysis of the crystal morphology was performed using the Bravais-Friedel, Donnay-Harker (BFDH) model. DTA analysis revealed that the NdAuIn phase melts congruently at 1136°C. The DFT-calculated enthalpy of formation is −774.192 meV/atom. A thermal expansion coefficient α = 4.1(3) × 10−5 K−1 was derived from the single crystal XRD measurements at 100, 200, and 300 K. The Sommerfeld coefficient γ of 1.262 (mJ/mol × K2) derived from the DFT calculations and the distribution of the density of electronic states, predict metallic conductivity for NdAuIn. The analysis of the charge density difference and Bader charge analysis show that the NdAuIn compound might be treated as polar intermetallic with negatively charged [AuIn]n− and positively charged Ndn+ sublattices. Magnetization measurements with the field parallel and perpendicular to the six-fold axis of the crystal revealed that NdAuIn is a Curie-Weiss paramagnet down to 25 K with an effective magnetic moment of ∼3.62 μB/Nd, which corresponds to the Nd3+ ion. The compound exhibits antiferromagnetic ordering at TN ∼2.4 K.

Ternary orthorhombic Laves phases Sr2Pd3Sn, Eu2Pd3Sn and Eu2Pd3In

Abstract The ternary Laves phases Sr2Pd3Sn, Eu2Pd3Sn and Eu2Pd3In were synthesized by induction melting of the elements in sealed tantalum ampoules. The polycrystalline products were characterized through their powder X-ray diffraction patterns. The structure of Eu2Pd3Sn was refined from single crystal X-ray diffractometer data: Mg2MnGa3 type, Cmcm, a = 583.36(5), b = 908.31(7), c = 958.06(8) pm, wR2 = 0.0366, 557 F 2 values, 23 variables. The palladium and tin atoms show the inverse coloring on the network of condensed tetrahedra of Mg2MnGa3, i.e., MnGa3 versus Pd3Sn. Refinement of the occupancy parameters revealed small defects for the europium site, leading to composition Eu1.962(6)Pd3Sn for the studied crystal. Sr2Pd3Sn is a Pauli paramagnet and Eu2Pd3Sn shows Curie-Weiss paramagnetism (7.86(1) µB Eu atom−1 and Θ P = 48.1(1) K). Ferromagnetic ordering is observed below T C = 46.1(1) K. The 119Sn and 151Eu Mössbauer spectra of Sr2Pd3Sn and Eu2Pd3Sn are discussed with respect to electron density changes as a function of the tin content and the ionicity in the sequence of the stannides Sr2Pd3Sn/Eu2Pd3Sn → Sr2Pd2Sn/Eu2Pd2Sn → EuPdSn → EuPdSn2.

Mössbauer-spectroscopic characterization of the stannides Sr2Pd2Sn and Eu2Pd2Sn

Abstract The Ca2Pd2Ge-type stannides Sr2Pd2Sn and Eu2Pd2Sn were synthesized by reaction of the elements in sealed tantalum ampoules in a high-frequency furnace and characterized by powder X-ray diffraction. The structure of Sr2Pd2Sn (Fdd2, a = 1063.95(5), b = 1623.22(9), c = 594.63(14) pm, wR2 = 0.0472, 972 F 2 values and 26 variables) was refined from single-crystal X-ray diffractometer data. The striking structural motif features equidistant chains formed by the palladium atoms (304.7 pm Pd–Pd), which are interlinked by the tin atoms (266.9 and 268.7 pm Pd–Sn). Together, the palladium and tin atoms form a three-dimensional [Pd2Sn] δ– polyanionic network in which the strontium atoms reside in larger cavities. The divalent character of europium in Eu2Pd2Sn was manifested by 151Eu Mössbauer spectroscopy. The isomer shift is δ = −9.48(1) mm s−1 at room temperature. The results of 119Sn Mössbauer-spectroscopic experiments have confirmed the tin site determined by the single-crystal study, the isomer shifts being δ = 1.71(1) mm s−1 for Eu2Pd2Sn and δ = 1.73(1) mm s−1 for Sr2Pd2Sn. Sr2Pd2Sn is a Pauli paramagnet with a susceptibility of 2.2(1) × 10−5 emu mol−1 at room temperature. Eu2Pd2Sn shows Curie-Weiss paramagnetism with an experimental magnetic moment of 7.85(1) µB per Eu atom, confirming divalent europium. The europium magnetic moments order antiferromagnetically at T N = 14 K.

Magnesium-rich intermetallic compounds Gd5Cu5Mg13 and Tb5Cu5Mg13 – intergrowth variants with CsCl and AlB2 related slabs

Abstract The magnesium-rich intermetallic compounds Gd5Cu5Mg13 and Tb5Cu5Mg13 were obtained from direct reactions of the elements (induction melting) in sealed tantalum ampoules. Both compounds crystallize with the orthorhombic Y5Cu5Mg13 type structure, space group Cmcm and Z = 4. The polycrystalline samples were characterized by powder X-ray diffraction. The structure of the gadolinium compound was refined from single crystal X-ray diffraction data: a = 414.78(2), b = 1921.87(12), c = 2573.89(16) pm, wR2 = 0.0492, 1611 F 2 values and 77 variables. Refinement of the occupancy parameters revealed a small degree of Gd/Mg mixing for the Gd3 site, leading to the composition Gd4.93(1)Cu5Mg13.07(1) for the studied crystal. The Gd5Cu5Mg13 structure contains slabs of equiatomic GdCuMg, which are embedded in a magnesium matrix. From a geometrical point of view, one can describe the Gd5Cu5Mg13 and Tb5Cu5Mg13 structures as intergrowth variants of distorted W/CsCl and AlB2 related slabs. The most remarkable crystal chemical feature concerns the bcc like magnesium slabs with short Mg–Mg distances ranging from 300 to 342 pm. Temperature dependent magnetic susceptibility measurements show Curie-Weiss paramagnetism for Tb5Cu5Mg13 (10.5(1) μ B Tb atom−1 and Θ P = −11.6(1) K). Antiferromagnetic ordering was detected below the Néel temperatures of T N = 30.5(3) K.

Salt-flux growth of HoCuMg4 single crystals.

Polycrystalline samples of the magnesium-rich intermetallic compounds RECuMg4 (RE = Dy, Ho, Er, Tm) were synthesized by reaction of the elements in sealed tantalum ampoules heated in a high-frequency induction furnace. Phase purity of the RECuMg4 phases was ascertained by powder X-ray diffraction patterns. Well-shaped single crystals of HoCuMg4 could be grown in a NaCl/KCl salt flux and the crystal structure was refined from single crystal X-ray diffraction data: TbCuMg4 structure-type, space group Cmmm, a = 1361.4(2), b = 2039.3(4), c = 384.62(6) pm. The crystal structure of the RECuMg4 phases can be understood as a complex intergrowth variant of CsCl and AlB2 related slabs. The remarkable crystal chemical motif concerns the orthorhombically distorted bcc-like magnesium cubes with Mg-Mg distances ranging from 306 to 334 pm. At high temperatures DyCuMg4 and ErCuMg4 are Curie-Weiss paramagnets with paramagnetic Curie-Weiss temperatures of -15 K and -2 K for RE = Dy and Er, respectively. The effective magnetic moments, 10.66μB for RE = Dy and 9.65μB for RE = Er prove stable trivalent ground states for the rare earth cations. Magnetic susceptibility and heat capacity measurements reveal long-range antiferromagnetic ordering at low temperatures (<21 K). Whereas DyCuMg4 exhibits two subsequent antiferromagnetic transitions at TN = 21 and 7.9 K which successively remove half of the entropy of a doublet crystal field ground state of Dy, ErCuMg4 shows a single, possibly broadened, antiferromagnetic transition at 8.6 K. The successive antiferromagnetic transitions are discussed with respect to magnetic frustration in the tetrameric units present in the crystal structure.

Magnetic susceptibility of one-dimensional spin chains S(Ni-=SUP=-2+-=/SUP=-)=1 single crystal Y-=SUB=-2-=/SUB=-BaNiO-=SUB=-5-=/SUB=- in the region of 1.85-800 K

The magnetic susceptibility of chi(T) one-dimensional spin chains (OSCs) of a single crystal Y2BaNi05 was first studied in the range of 1.85-800 K. In the region from 800 to ~520 the OCC exhibits Curie-Weiss paramagnetism, in which chi0(T)=C/(T+800), where C is the Curie constant, with an effective magnetic moment of μeff=3.75 μB. With a decrease from 520 to 40 K, the susceptibility changes as a Halden magnet with a gap Delta=117 K, chi(T)=chi0(T)exp(-117/T). Below 40 K chi(T) grows again according to the Curie-Weiss law with μeff=3.75μB, thetai1=-3 K and ni1=9.3·1019 spins S(Ni2+)=1 per mole in a crystal grown in an oxygen-free environment; and thetai2=-1.3 K, and ni2=4.6·1019 spins S(Ni2+)=1 after annealing this crystal to 1000oC in air and its subsequent slow cooling.Such a change in the &amp;quot;impurity&amp;quot; contribution to chi(T) of the OCC is presumably due to a lack of O2 in a significant proportion of the terminal spins in the OCC of a single crystal Keywords: energy gap, SQUID measurements in the region of 1.85-800 K, end spins, breaks in the spin chain.

New ternary aluminides Ce0.67Pd2Al5, Ce1.33Pd3Al8, and Ce1.74Pd5.29Al11.71

Polycrystalline samples of novel compounds Ce 0.67 Pd 2 Al 5 , Ce 1.33 Pd 3 Al 8 , and Ce 1.74 Pd 5.29 Al 11.71 were prepared by arc-melting. The crystal structure of the latter compound was determined from the single-crystal X-ray diffraction data to be a disordered variant of the hexagonal Th 2 Ni 17 type [ P 6 3 / mmc , a = 9.1961(5) Å, c = 8.8861(5) Å]. The crystal structures of the other aluminides were examined by powder X-ray diffraction and found to be isotypic with Sc 0.67 Fe 2 Si 5 [ P 6 3 / mmc , a = 4.3385(5) Å, c = 16.5255(15) Å] and Gd 1.33 Pt 3 Al 8 [ R 3 ¯ m , a = 4.37960(10) Å, c = 39.1683(9) Å], respectively. Based on the thermodynamic and electrical resistivity data measured down to 0.4 K in external magnetic fields up to 9 T, the new materials were characterized as metallic Curie-Weiss paramagnets due to fairly stable trivalent Ce ions. In Ce 1.33 Pd 3 Al 8 , an antiferromagnetic ordering was established below T N = 2.3 K, while no long-range magnetic order was found in the other compounds. All three phases exhibit electrical conductivity that is governed by the interplay of Kondo and crystalline electric field interactions, and significantly affected by structural disorder inherent to their crystal lattices. • Novel compounds Ce 0.67 Pd 2 Al 5 , Ce 1.33 Pd 3 Al 8 , and Ce 1.74 Pd 5.29 Al 11.71 were synthesized. • They form with Sc 0.67 Fe 2 Si 5 , Gd 1.33 Pt 3 Al 8 , and Th 2 Ni 17 structure types, respectively. • Electrical transport is strongly affected by structural disorder and Kondo effect.. • They are Curie-Weiss paramagnets; Ce 1.33 Pd 3 Al 8 orders antiferromagnetically at 2.3 K.

Magnesium-rich intermetallic compounds RE 3Ag4Mg12 (RE = Y, La–Nd, Sm–Dy, Yb) and AE 3Ag4Mg12 (AE = Ca, Sr)

Abstract The magnesium-rich intermetallic compounds RE 3Ag4Mg12 (RE = Y, La–Nd, Sm–Dy, Yb) and AE 3Ag4Mg12 (AE = Ca, Sr) were synthesized from the elements in sealed tantalum ampoules through heat treatment in an induction furnace. X-ray powder diffraction studies confirm the hexagonal Gd3Ru4Al12 type structure, space group P63/mmc. Three structures were refined from single crystal X-ray diffractometer data: a = 973.47(5), c = 1037.19(5) pm, wR2 = 0.0296, 660 F 2 values, 30 variables for Gd3Ag3.82(1)Mg12.18(1), a = 985.27(9), c = 1047.34(9) pm, wR2 = 0.0367, 716 F 2 values, 29 variables for Yb3Ag3.73(1)Mg12.27(1) and a = 992.41(8), c = 1050.41(8) pm, wR2 = 0.0373, 347 F 2 values, 28 variables for Ca3Ag3.63(1)Mg12.37(1). Refinements of the occupancy parameters revealed substantial Ag/Mg mixing within the silver-magnesium substructure, a consequence of the Ag@Mg8 coordination. The alkaline earth and rare earth atoms build Kagome networks. Temperature dependent magnetic susceptibility measurements indicate diamagnetism/Pauli paramagnetism for the compounds with Ca, Sr, Y and YbII, while the others with the trivalent rare earth elements are Curie-Weiss paramagnets. Most compounds order antiferromagnetically at T N = 4.4(1) K (RE = Pr), 34.6(1) K (RE = Gd) and 23.5(1) K (RE = Tb) while Eu3Ag4Mg12 is a ferromagnet (T C = 19.1(1) K). 151Eu Mössbauer spectra confirm divalent europium (δ = −9.88(1) mm s−1). Full magnetic hyperfine field splitting (18.4(1) T) is observed at 6 K. Yb3Ag4Mg12 shows a single resonance in its 171Yb solid state NMR spectrum at 6991 ppm at 300 K indicating a strong, positive Knight shift.

Intermetallic compounds RE 2Ga2Mg (RE = Tb–Tm, Lu) with Mo2B2Fe-type structure

Abstract The rare earth intermetallic compounds RE 2Ga2Mg with RE = Tb–Tm and Lu were synthesized from the elements in sealed tantalum ampoules in a high-frequency furnace. These rare earth-rich phases crystallize with the tetragonal Mo2B2Fe-type structure, space group P4/mbm and Z = 2. The polycrystalline samples were characterized through their Guinier powder patterns. The structures of Er2Ga2.092(1)Mg0.908(1), Tm2Ga2.037(1)Mg0.963(1) and Lu2Ga2.176(1)Mg0.824(1) have been refined from single crystal X-ray diffractometer data. The refinements revealed small homogeneity ranges (small degrees of Mg/Ga mixing on the 2a sites). The magnesium atoms show square planar coordination by Ga2 dumbbells (282 pm Mg–Ga and 257 pm Ga–Ga in the lutetium compound). Geometrically one can describe the RE 2Ga2Mg phases as 1:1 intergrowth structures of CsCl and AlB2-related slabs of compositions REMg and REGa2. From DFT based calculations, charge transfer from the rare earth and magnesium atoms towards gallium can be illustrated in electron localization function ELF slice planes showing strong localization around gallium in the basal plane as well as along the tetragonal c axis signaling Ga–Ga pair interactions. The site-projected density of states DOS and COOP data further quantify this observation. Temperature dependent magnetic susceptibility measurements show Pauli paramagnetism for Sc2Ga2Mg and Lu2Ga2Mg with low room temperature susceptibility values of 2.1(1) × 10−4 and 1.1(1) × 10−4 emu mol−1, respectively. Ho2Ga2Mg, Er2Ga2Mg and Tm2Ga2Mg are Curie-Weiss paramagnets with stable trivalent rare earth ground states. Antiferromagnetic ordering was detected below the Néel temperatures of T N = 18.6(1) (RE = Ho), 11.9(1) (RE = Er) and 6.4(1) K (RE = Tm). The three compounds show metamagnetic transitions in their 3 K magnetization isotherms. Tm2Ga2Mg exhibits a square loop behavior with small hysteresis.

Crystal structure and magnetic properties of some compounds with GdNi2Ga3In type structure

Abstract The GdNi2Ga3In type crystal structures (Pnma) of the quaternary intermetallic compounds TbNi2Ga3.03(1)In0.97(1) (a = 2.41554(2), b = 0.41614(4), c = 0.92220(10) nm, wR2 = 0.0512, 2006 F 2 values, 90 parameters) and HoNi2Ga3.03(2)In0.97(2) (a = 2.41822(7), b = 0.41400(15), c = 0.9199(3) nm, wR2 = 0.0588, 1980 F 2 values, 89 parameters) were refined from the single crystal X-ray diffraction data. Single crystals were obtained by high-frequency annealing of the samples in sealed tantalum ampoules. The compounds with RE = Y, Dy and Ho are isotypic and were characterized by powder X-ray diffraction. The magnetic behaviour of the compounds RENi2Ga3In (RE = Y, Dy, Ho) was characterized by means of magnetization and dc magnetic susceptibility measurements, carried out in the temperature range 1.72–400 K in external magnetic fields up to 5 T. YNi2Ga3In was found to be a Pauli paramagnet with a molar magnetic susceptibility of about 4⋅10−5 emu mol−1 at room temperature. DyNi2Ga3In and HoNi2Ga3In are Curie-Weiss paramagnets which order antiferromagnetically below T N = 10.5 K (DyNi2Ga3In) and 4.4 K (HoNi2Ga3In).

Bcc superstructures: RE2RuIn with RE = Sc, Y, Dy-Tm and Lu.

The rare earth-rich intermetallic phases RE2RuIn with RE = Sc, Y, Dy-Tm and Lu were synthesized by reactions of the elements in sealed tantalum ampoules in an induction furnace. The samples were characterized through Guinier powder patterns and the structures of Sc2RuIn and Er2RuIn were refined from single crystal X-ray diffraction data. The indides crystallize with the Pt2ZnCd type space group P4/mmm. The RE2RuIn phases are superstructures of the bcc packing and can be explained as intergrowth variants of tetragonally distorted, CsCl derived slabs of compositions RERu and REIn. Chemical bonding is discussed for Sc2RuIn and Sc2RuMg in comparison with the binaries ScRu, ScMg and ScIn. The Ru/Mg respectively Ru/In ordering leads to an increase of Sc-Sc bonding for the slab with the shorter Sc-Sc distances, while the Sc-Ru bond strength values remain similar. The strongest bonding interactions occur within the magnesium and indium square nets. Magnetic susceptibility measurements reveal Pauli paramagnetism for Lu2RuIn while Dy2RuIn, Ho2RuIn, Er2RuIn and Tm2RuIn are Curie-Weiss paramagnets. Antiferromagnetic ordering occurs at 13.1, 5.3 and 2.9 K for Dy2RuIn, Er2RuIn and Tm2RuIn, respectively. Dy2RuIn and Er2RuIn show metamagnetic transitions at critical fields of 4.6 and 3.2 T.

Laves Phase Formation in High Entropy Alloys

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x = 12x-VCrMoMnFe, 12x + Sc, 12x + Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x + Be alloy reveals a single-phase C14 structure with a very high concentration of structural defects and ultra-fine dendritic microstructure with an almost homogenous distribution of the constituted elements over the alloy matrix. The analysis of electrical and magnetic properties reveals that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggest that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band.

Tm4IrIn and Lu4PtIn – In4 tetrahedra embedded in RE 22 polyhedra

Abstract The rare earth-rich indides Tm4IrIn and Lu4PtIn were synthesized by reaction of the elements in sealed tantalum ampules in an induction furnace. Tm4IrIn (a = 1340.77(4) pm) and Lu4PtIn (a = 1338.0(1) pm) crystallize with the Gd4RhIn-type structure, space group F 4 ‾ 3 m $F\overline{4}3m$ . The Lu4PtIn structure was refined from single crystal X-ray diffractometer data: wR = 0.0524, 517 F 2 values and 20 variables. The striking crystal chemical motif is the fcc packing of In4 tetrahedra with 318 pm In–In. The Lu4PtIn structure is closely related to the structures of Lu13Ni6In, Lu14Pd3In3 and Lu20Ir5In3 which all show icosahedral indium coordination and different condensation patterns that build up the indium substructure that consists of a dumbbell in Lu14Pd3In3 and a triangle in Lu20Ir5In3. The results of magnetic susceptibility measurements indicate Curie-Weiss paramagnetism for Tm4IrIn (7.76(1) µB per thulium atom) without magnetic ordering down to 2.5 K. Lu4PtIn is Pauli-paramagnetic.

The ternary platinides CaGa5Pt3 and EuGa5Pt3

Abstract The ternary platinides CaGa5Pt3 (a = 2082.5(4), b = 406.05(8), c = 739.2(1) pm) and EuGa5Pt3 (a = 2085.5(5), b = 412.75(9), c = 738.7(1) pm) were synthesized from the elements in sealed high-melting metal tubes in an induction furnace. CaGa5Pt3 and EuGa5Pt3 are isotypic with CeAl5Pt3 and isopointal with the YNi5Si3 type intermetallic phases (space group Pnma, oP36 and Wyckoff sequence c 9). The structure of EuGa5Pt3 was refined from single crystal X-ray diffractometer data: wR2 = 0.0443, 1063 F 2 values and 56 variables. The gallium and platinum atoms build up a three-dimensional [Ga5Pt3]2− polyanionic network in which the europium atoms fill slightly distorted hexagonal prismatic voids. The Ga–Pt distances within the network range from 249 to 271 pm, emphasizing the covalent bonding character. Temperature dependent magnetic susceptibility measurements indicate diamagnetism for CaGa5Pt3 and isotypic BaGa5Pt3. EuGa5Pt3 behaves like a Curie–Weiss paramagnet above 50 K with an experimental magnetic moment of 8.17(1) µB/Eu atom, indicating divalent europium. Antiferromagnetic ordering sets in at T N = 8.5(1) K. The divalent ground state of europium is confirmed by 151Eu Mössbauer spectroscopy. EuGa5Pt3 shows a single signal at 78 K with an isomer shift of −9.89(4) mm s−1. Full magnetic hyperfine splitting with a hyperfine field of 25.0(2) T is observed at 6 K in the magnetically ordered regime.

Pressure effects on electronic structure and electrical conductivity of TiZrHfNb high-entropy alloy

Due to specific highly distorted crystalline structure, high-entropy alloys (HEAs) are expected to demonstrate interesting behavior under high pressures. However, this issue is not yet well studied. Here we address pressure effects on electronic structure and electrical conductivity of TiZrHfNb alloy. Among the multiplicity of single-phase HEAs explored so far, the TiZrHfNb one is an exemplar of thermally stable metallic material that crystallizes into body-centered cubic (BCC) structure and demonstrates excellent mechanical, corrosion, and friction properties compared to conventional alloys. We synthesize this material with BCC structure and analyze its electrical, superconducting, and magnetic properties. The alloy is a Curie-Weiss paramagnet and a type-II superconductor with the critical temperature of about 6.3 K. The estimated upper critical field and critical current density in the HEA are rather moderate compared to those observed in the superconductors based on Ti–Nb alloys. In the normal state, the alloy demonstrates high electrical resistance that practically independent of temperature but significantly dependent on pressure; it decreases linearly by 12.5% as the pressure increases up to 5.5 GPa. By analyzing the experimental data, we suggest that alloy resistance is mainly determined by two contributions: the residual resistance and Mott's s-d scattering. We show that a cooperative effect from changes in both the Debye temperature and electronic band structure near the Fermi level are the main factors responsible for the electrical resistance behavior of the HEA under pressure. Ab initio calculations performed at different pressures support this conclusion. The results show that TiZrHfNb alloy is a promising material for designing resistance pressure gauges.

A europium kagome lattice in the solid solution Eu3−х Sr х Pt4Zn12 – first zinc representatives of the Gd3Ru4Al12 type

Abstract Eu3Pt4Zn12 and Sr3Pt4Zn12 form a complete solid solution Eu3−x Sr x Pt4Zn12. Samples with x = 0, 0.5, 1, 1.5, 2, 2.5 and 3 were synthesized from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by powder X-ray diffraction and the structures of Sr3Pt3.93Zn12.07, Eu1.80Sr1.20Pt4Zn12 and Eu3Pt3.68Zn12.32 were refined from single crystal X-ray diffractometer data. The new compounds are isotypic with Gd3Ru4Al12, space group P63/mmc. The striking building units in these phases are the kagome networks occupied by the europium and strontium atoms and Pt1@Zn8 and Pt2@Zn8 distorted cubes. Besides the Eu/Sr mixing within the solid solution, the structure refinements indicated small homogeneity ranges induced by Pt/Zn mixing. The europium containing samples of the solid solution Eu3−x Sr x Pt4Zn12 are Curie–Weiss paramagnets and the experimental magnetic moments manifest stable divalent europium. The samples with x = 0, 0.5 and 2 order magnetically: T N = 15.4(1) K for x = 0, T C = 12.4(1) K for x = 0.5 and T N = 4.0(1) K for x = 2. The 3 K magnetization isotherms tend toward Brillouin type behavior with increasing europium dilution. The divalent ground state of Eu3Pt4Zn12 is further confirmed by 151Eu Mössbauer spectroscopy with an isomer shift of −9.66(2) mm s−1 at 78 K. In the magnetically ordered state Eu3Pt4Zn12 shows full magnetic hyperfine field splitting (23.0(1) T).