The magnetic structure of EuPdSn

Crystal Structure and Magnetism of Noncentrosymmetric Eu2Pd2Sn

The new intermetallic compound Eu₂Pd₂Sn has been investigated. A single crystal was selected from the alloy and was analyzed by single-crystal X-ray diffraction, revealing that this compound possesses the noncentrosymmetric Ca₂Pd₂Ge structure type being, so far, the only rare-earth-based representative. Bonding analysis, performed on the basis of DOS and (I)COHP, reveals the presence of strong covalent Sn–Pd bonds in addition to linear and equidistant Pd–Pd chains. The incomplete ionization of Eu leads to its participation in weaker covalent interactions. The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μ_eff = 7.87 μ_B, close to the free ion Eu²⁺ value (μ_eff = 7.94 μ_B). The maximum of χ(T) at T_N ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat C_P(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at T_N a scenario of a transition to an incommensurate antiferromagnetic phase below T_N followed by a commensurate configuration below 10 K is suggested.

A new intermetallic compound, Eu₂Pd₂Sn, is so far the only rare-earth representative of the Ca₂Pd₂Ge structure type. Synthesis and characterization of the structure, together with magnetic properties, are discussed.

Intermetallics of the types REPd3 X 2 and REPt3 X 2 (RE=La–Nd, Sm, Gd, Tb; X=In, Sn) with substructures featuring tin and In atoms in distorted square-planar coordination

The intermetallic compounds RET 3 X 2 (RE = La–Nd, Sm, Gd, Tb; T = Pd, Pt; X = In, Sn) have been synthesized from the elements by arc-melting and subsequent annealing sequences in tube or induction furnaces. The samples were characterized through Guinier powder diffraction patterns, and several structures were refined from single crystal X-ray diffractometer data. These indium and tin intermetallics crystallize with the orthorhombic CePd3In2-type structure, space group Pnma. The palladium (platinum) and indium (tin) atoms in the RET 3 X 2 structures build up complex three-dimensional [T 3 X 2] δ− polyanionic networks in which the rare earth atoms fill cavities. The striking structural motifs concern the indium, respectively tin substructures, in which part of the indium and tin atoms have distorted square planar homoatomic coordination environments: In1In12In22 units in PrPd3In2 with interatomic distances 325 pm In1–In1 and 332 pm In1–In2 as well as Sn1Sn12Sn22 units in PrPt3Sn2 with the larger distances of 356 pm for Sn1–Sn1 and of 344 pm for Sn1–Sn2. Temperature dependent magnetic susceptibility measurements have indicated Pauli paramagnetism or diamagnetism for the lanthanum compounds, van-Vleck paramagnetism for SmPt3In2 and Curie-Weiss paramagnetism for the remaining compounds. Antiferromagnetic ordering was detected at T N = 4.0(1) K for CePt3In2 and at T N = 3.5(1) K for SmPt3In2. CePt3In2 shows a metamagnetic transition at an external magnetic field of 47(3) kOe.

Crystal structure and physical properties of the two stannides EuPdSn2 and YbPdSn2

We report on synthesis, crystal structure and physical properties of the isotypic compounds YbPdSn₂ and EuPdSn₂ crystallizing in the MgCuAl₂-type structure. In both stannides a divalent state of respective rare earth element was found from analysis of the magnetic susceptibilities. Whereas in YbPdSn₂ only weak paramagnetic behaviour is observed, in EuPdSn₂ a long-range magnetic phase transition occurs at 12.5 K with complex magnetic behaviour evidenced by magnetic susceptibity and specific heat measurements. Under the influence of magnetic field, the magnetic behaviour was found to evolve from an antiferromagnetic to a ferromagnetic state as a consequence of a re-arrangement of magnetic moments.

Magnetic, specific heat and electrical transport properties of Frank-Kasper cage compounds RTM2Al20 [R = Eu, Gd and La; TM = V, Ti]

Single crystals of Frank-Kasper compounds RTM2Al20 (R  =  Eu, Gd and La; TM  =  V and Ti) were grown by self-flux method and their physical properties were investigated through magnetization (M), magnetic susceptibility (χ), specific heat (C P) and electrical resistivity (ρ) measurements. Powder x-ray diffraction studies and structural analysis showed that these compounds crystallize in the cubic crystal structure with the space group [Formula: see text]. The magnetic susceptibility for the compounds EuTi2Al20 and GdTi2Al20 showed a sudden jump below the Néel temperature T N indicative of plausible double magnetic transition. Specific heat (C P) and electrical resistivity (ρ) measurements also confirm the first-order magnetic transition (FOMT) and possible double magnetic transitions. Temperature variation of heat capacity showed a sharp phase transition and huge C P value for the (Eu/Gd)Ti2Al20 compounds' full width at half-maximum (FWHM) (<0.2 K) which is reminiscent of a first-order phase transition and a unique attribute among RTM2Al20 compounds. In contrast, linear variation of C P is observed in the ordered state for (Eu/Gd)V2Al20 compounds suggesting a λ-type transition. We observed clear anomaly between heating and cooling cycle in temperature-time relaxation curve for the compounds GdTi2Al20 (2.38 K) and EuTi2Al20 (3.2 K) which is indicating a thermal arrest due to the latent heat. The temperature variation of S mag for GdTi2Al20 saturates to a value [Formula: see text] while the other magnetic systems exhibited still lower entropy saturation values in the high temperature limit. [Formula: see text] versus T plot showed a maximum near 27 K for all the compounds indicating the presence of low frequency Einstein modes of vibrations. Resistivity measurements showed that all the samples behave as normal Fermi liquid type compounds and [Formula: see text] due to electron-phonon scattering follows Bloch-Grüneisen-Mott relation in the paramagnetic region.

Europium and manganese magnetic ordering in EuMn2Ge2

The antiferromagnetic structures of both the manganese and europium sublattices in EuMn2Ge2 have been determined using thermal neutron diffraction. T(N)(Mn)  =  714(5) K with the 3.35(5) μ(B) (at 285 K) Mn moments ordering according to the I4'/m'm'm space group. The Eu order is incommensurate with the 6.1(2) μ(B) (at 3.6 K) Eu moments oriented parallel to the c-axis with a propagation vector of k  =  [0.153(2) 0 0]. Both neutron diffraction and (151)Eu Mössbauer spectroscopy reveal evidence of magnetic short-range ordering of the Eu sublattice around and above T(N)(Eu)  ∼ 10 K. The ordering temperature of the Eu sublattice is strongly affected by the sample's thermal history and rapid quenching from the melting point may lead to a complete suppression of that ordering.

Ferrimagnetism in GdCo(12-x)Fe(x)B6

The effects of iron substitution on the structural and magnetic properties of the GdCo(12-x)Fe(x)B6 (0 ≤ x ≤ 3) series of compounds have been studied. All of the compounds form in the rhombohedral SrNi12B6-type structure and exhibit ferrimagnetic behaviour below room temperature: T(C) decreases from 158 K for x = 0 to 93 K for x = 3. (155)Gd Mössbauer spectroscopy indicates that the easy magnetization axis changes from axial to basal-plane upon substitution of Fe for Co. This observation has been confirmed using neutron powder diffraction. The axial to basal-plane transition is remarkably sensitive to the Fe content and comparison with earlier (57)Fe-doping studies suggests that the boundary lies below x = 0.1.