ZrCuSiAs-type Structure Research Articles

Drastic enhancement of electronic correlations induced by hydrogen insertion in the cerium intermetallic compound CeFeSi.

We report a comparative study of two cerium-based intermetallic compounds: CeFeSi with an anti-PbFCl type structure, and CeFeSiH with a ZrCuSiAs type structure. The latter is obtained from CeFeSi through hydrogen insertion. Our results are based on X-rays, transport, thermodynamic and magnetic measurements. While the tetragonal structure with P4/nmm symmetry remains unchanged after hydrogen insertion, the thermodynamic, magnetic, and transport properties change drastically. On the one hand, CeFeSi behaves as a Pauli paramagnet with a small Sommerfeld coefficient, indicating the absence of 4f electron physics. On the other hand, our study shows that CeFeSiH exhibits strong magnetic fluctuations with a magnetic transition at 3.5 K, and coherent Kondo-lattice heavy-fermion features.

Observation of spin-glass behavior in 1111-type magnetic semiconductor (La, Ba)(Zn, Mn)SbO

We report the successful fabrication of a new 1111-type bulk magnetic semiconductor (La,Ba)(Zn,Mn)SbO through the solid solution of (La,Ba) and (Zn,Mn) in the parent compound LaZnSbO. The polycrystalline samples (La,Ba)(Zn,Mn)SbO crystallize into ZrCuSiAs-type tetragonal structure, which has the same structure as iron-based superconductor LaFeAsO1–δ . The DC magnetization measurements indicate the existence of spin-glass ordering, and the coercive field is up to ∼11500 Oe (1 Oe = 79.5775 A⋅m−1). The AC magnetic susceptibility further determines that the samples evolve into a conventional spin-glass ordering state below the spin freezing temperature T f. In addition, the negative magnetoresistance (MR ≡ [ρ(H)–ρ(0)]/ρ(0)) reaches −88% under 9 T.

Superconductivity and magnetism in a novel La0.85Ga0.15FeAsO compound

We report magnetization measurements on samples of La0.85Ga0.15FeAsO in the wide temperature range of 10 K-400 K, up to the field of 90 kOe having been prepared by solid-state reaction. This novel compound crystallizes with the tetragonal ZrCuSiAs-type structure. The crystal structure was determined by X-ray powder diffraction (P4/nmm: a = 4.032 Å, and c = 8.741 Å).Temperature dependence of magnetization for this compound is measured with zero-field cooling (ZFC) and field cooling (FC) with an application of H = 50 Oe. The large bifurcation between the ZFC and FC curves has been observed starting at around 370 K. At lower temperatures below Tscset−on∼37 K, superconductivity and magnetism coexist. Intermediate temperature range (37 K< T < 300 K), the sample is in a mixed state of the ferromagnetic clusters with paramagnetic moments, described well by the Modified Curie Weiss expression. At higher temperatures above 360 K, it is a pure paramagnetic, described perfectly by the simple Curie-Weiss expression.The natures of the superconducting flux-pinning centers are revealed based on analysis of the pinning force, Fpin at T = 10 K. The normalized pinning force, Fp/Fp, max versus H indicates the filamentary character owing to the pinning parameters, p = 0.5, q = 2. These results point out that, in the superconductivity, the dominance of grain boundary with single-vortex pinning (μ =1/7) mechanismThe Curie temperature, Tcurie was estimated using the modified Arrot plots. The critical exponents, β, ϒ, and δ were estimated, and their values are in close agreement with those predicted for a mean-field-like behavior at a magnetic phase transition.

Assessment of the thermoelectric performance of layered semiconductor SrFCuTe with wide band-gap

The concept of “phonon-glass, electron-crystal” promotes the development of designing thermoelectric compounds through building functional blocks. Alternately stacking insulating [Sr2F2]2+ layers and conductive [Cu2Te2]2- layers along the c-axis can construct wide-band-gap semiconductor SrFCuTe with the ZrCuSiAs-type structure. The thermoelectric characterization reveal that this compound has considerably low p-type conductivity and thermal conductivity. Na substitution Sr can significantly improve the electrical transport properties due to the acceptor-doping effect, while it increases the electronic thermal conductivity simultaneously. The synergistic effect makes the thermoelectric figure of merit zT rise about 100% at 773 ​K. This work demonstrates that wide-band-gap semiconductors undergoing rational performance manipulation, worthy of reassessing for thermoelectric application.

A new oxygen-free cobalt-based compound SmCoAsF with multiple magnetic transitions

A new quaternary oxygen-free cobalt-based compound SmCoAsF, which crystallizes with the tetragonal ZrCuSiAs-type structure, is synthesized via a solid state metathesis reaction.

A Self-Doped Oxygen-Free High-Critical-Temperature (High-Tc) Superconductor: SmFFeAs.

A new iron-base superconductor SmFFeAs is synthesized via solid-state metathesis reaction by using SmFCl and LiFeAs as precursors. The compound crystallized in the tetragonal ZrCuSiAs-type structure with the space group P4/nmm and lattice parameters of a = 3.9399(0) Å and c = 8.5034(1) Å. The superconducting diamagnetic transition occurs at 56 K for the parent compound, which confirmed by the resistivity and magnetic susceptibility. The appearance of superconductivity without extrinsic doping could be ascribed to the self-doping owing to the mixed valence of Sm ions. The as-synthesized SmFFeAs serves as a new self-doped parent compound for oxygen-free high-critical-temperature (high-Tc) superconductors.

Ferromagnetism in fluoride-antimonide SrF(Zn1-2xMnxCux)Sb with a quasi two dimensional structure

Abstract We report the synthesis and characterization of a new bulk form fluoride-antimonide diluted magnetic semiconductor SrF( Zn 1 - 2 x Mn x Cu x )Sb with ZrCuSiAs-type structure, which is the same quasi-two-dimensional crystal structure as that of 1111-type iron-based superconductors. Doping only Cu into the parent compound SrFZnSb does not induce any type of magnetic ordering. Only when Mn and Cu are codoped into Zn sites, where Mn substitution for Zn and Cu substitution for Zn introduce spins and carriers, respectively, can ferromagnetic ordering form. Bulk form samples SrF( Zn 1 - 2 x Mn x Cu x )Sb with x = 0.05, 0.075, 0.10 and 0.15 exhibit ferromagnetic transition, with highest T C ∼ 40 K for the doping level of x = 0.10. Iso-thermal magnetization measurements show that they have a relatively larger coercive field ∼ 8000 Oe. The electrical resistivity measurements indicate that SrF( Zn 1 - 2 x Mn x Cu x )Sb DMSs display semiconducting behavior, with the negative magneto-resistance effect up to 27% under 9 T at 2 K.

Enhanced superconductivity in ThNiAsN

We report the synthesis and physical properties of a nickel-based arsenide ThNiAsN. The new compound crystallizes in a ZrCuSiAs-type structure (space group ) with lattice parameters and . Bulk superconductivity at is demonstrated by the measurements of electrical resistivity, dc magnetic susceptibility, and heat capacity. The upper critical field at zero temperature, , and the specific-heat jump at Tc are 6.1 T and , respectively. These two physical quantities, together with the Tc value, are the highest among the Ni-based ZrCuSiAs-type materials. We discuss this enhanced superconductivity in terms of the internal chemical pressure in ThNiAsN.

New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping

We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the “1111” iron-based superconductors. The joint hole doping via (Ba,K) substitution & spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments.

Structural stability at high pressure, electronic, and magnetic properties of BaFZnAs: A new candidate of host material of diluted magnetic semiconductors**Project supported by the National Natural Science Foundation of China and Project of Ministry of Science and Technology of China.

The layered semiconductor BaFZnAs with the tetragonal ZrCuSiAs-type structure has been successfully synthesized. Both the in-situ high-pressure synchrotron x-ray diffraction and the high-pressure Raman scattering measurements demonstrate that the structure of BaFZnAs is stable under pressure up to 17.5 GPa at room temperature. The resistivity and the magnetic susceptibility data show that BaFZnAs is a non-magnetic semiconductor. BaFZnAs is recommended as a candidate of the host material of diluted magnetic semiconductor.

A New ZrCuSiAs-Type Superconductor: ThFeAsN

We report the first nitrogen-containing iron-pnictide superconductor ThFeAsN, which is synthesized by a solid-state reaction in an evacuated container. The compound crystallizes in a ZrCuSiAs-type structure with the space group P4/nmm and lattice parameters a = 4.0367(1) Å and c = 8.5262(2) Å at 300 K. The electrical resistivity and dc magnetic susceptibility measurements indicate superconductivity at 30 K for the nominally undoped ThFeAsN.

Structure, magnetic properties and magnetocaloric effect in LaMnSbO0.8 F0.2 oxypnictide material

We have investigated the structural, magnetic properties and magnetocaloric effect (MCE) in LaMnSbO0.8F0.2. The compound has the ZrCuSiAs-type structure with P4/nmm space group. For a field change of 0–5 T, the maximum entropy change (–ΔSM) is calculated to be 0.074 J kg−1 K by using the Maxwell's relations from the magnetic isotherms. The relative cooling power was increasing from 0.67 to 3.74 J kg−1 with the increases of magnetic field changes from 0–1 to 0–5 T. The observed reversible MCE is related to a second-order magnetic phase transition.

Synthesis and Properties of 5d Electron-Doped CeFe1−x Ir x AsO Compounds

The nonmagnetic 5d transition metal Ir has been successfully doped at Fe site in CeFeAsO using a solid-state reaction method. The synthesized CeFe1−x Ir x AsO (x = 0, 0.05, 0.1, 0.15, 0.2) compounds possess the tetragonal ZrCuSiAs-type structure with the space group P4/nmm. It can be observed that the spin-density wave in CeFeAsO is definitely suppressed by Ir doping. Different from the cases in SmFeAsO and GdFeAsO, Ir doping in CeFeAsO can not induce superconductivity down to 5 K, instead, semiconductor-like behavior is observed in the present system.

Superconductivity in a new layered bismuth oxyselenide: LaO0.5F0.5BiSe2

We report superconductivity at Tc ≈ 2.6 K in a new layered bismuth oxyselenide LaO0.5F0.5BiSe2 with the ZrCuSiAs-type structure composed of alternating superconducting BiSe2 and blocking LaO layers. The superconducting properties of LaO0.5F0.5BiSe2 were investigated by means of dc magnetization, resistivity and muon-spin rotation experiments, revealing the appearance of bulk superconductivity with a rather large superconducting volume fraction of ≈ 70% at 1.8 K.

CeNi1-xSb1+yBi1-y Phases with ZrCuSiAs-type and CeNi1.26Sb2 with CaBe2Ge2-type Structure

Block- and platelet-shaped single crystals of several CeNi1-xSb1+yBi1-y phases with ZrCuSiAstype structure (space group P4=nmm) were grown from a CeNiSb precursor in bismuth fluxes. The structures of CeNiSb1.19Bi0.81, CeNi0.80Sb1.16Bi0.84 and CeNi0.75Sb1.74Bi0.26 were refined from single-crystal X-ray diffractometer data. The 2b nickel site can be fully or partially occupied, and the bismuth square nets show solid solutions with antimony. CaBe2Ge2-type CeNi2-xSb2 crystals occur as by-products of the crystal growth experiments. The structure of a CeNi1.26Sb2 crystal has been refined. The small difference of the compositions hamper phase analytical studies by powder X-ray diffraction. A polycrystalline CeNiSbBi sample showed Curie-Weiss behavior with an experimental magnetic moment of 2.56(1) μB per Ce atom, indicating purely trivalent cerium. No magnetic ordering is detected down to 2:5 K. A 121Sb Mössbauer spectrum showed an isomer shift of δ = -8.06(6)mms-1, substantiating the antimonide character.

Magnetic Structure and Electromagnetic Properties of LnCrAsO with a ZrCuSiAs-type Structure (Ln = La, Ce, Pr, and Nd)

We report the synthesis, structure, and electromagnetic properties of Cr-based layered oxyarsenides LnCrAsO (Ln = La, Ce, Pr, and Nd) with a ZrCuSiAs-type structure. All LnCrAsO samples showed metallic electronic conduction. Electron doping in LaCrAsO by Mn-substitution for the Cr sites gave rise to a metal-insulator transition. Analysis of powder neutron diffraction data revealed that LaCrAsO had G-type antiferromagnetic (AFM) ordering, i.e., a checkerboard-type AFM ordering in the CrAs plane and antiparallel spin coupling between the adjacent CrAs planes, at 300 K with a large spin moment of 1.57 μB along the c axis. The magnetic susceptibility of LaCrAsO was very small (on the order of 10(-3) emu/mol) and showed a broad hump at ∼550 K. First-principles density functional theory calculations of LaCrAsO explained its crystal structure and metallic nature well, but could not replicate the antiparallel spin coupling between the CrAs layers. The electronic structure of LaCrAsO is discussed with regard to those of related compounds LaFeAsO and LaMnAsO.

Bulk compound synthesis and oxygen deficiency effect on electronic and magnetic properties of the Zn-based oxyarsenide LaZnAsO1−δ

• Polycrystalline bulk compound LaZnAsO was synthesized for the first time. • Oxygen deficiency was introduced up to 35 at.% under a high pressure of 6 GPa. • The semiconductivity was highly robust against the oxygen deficiency up to 25 at.%. LaZnAsO has been studied mainly in the thin film form that was indicated as a wide-gap insulator with the gap size of ∼2.3 eV. We herein report the synthesis of polycrystalline bulk LaZnAsO compound for the first time under a high pressure of 6 GPa. Effect of oxygen deficiency on the electric and magnetic properties of the compound was also investigated by synchrotron X-ray diffraction and measurements of electrical resistivity, magnetic susceptibility, isothermal magnetization, and specific heat. The bulk LaZnAsO crystallized into the ZrCuSiAs-type structure with the space group P 4/ nmm , isostructural with the layered LaFeAsO . It is semiconducting with a thermal activation energy of ∼0.8 eV, and the semiconductivity was highly robust against oxygen deficiency up to 25 at.%. The virtue will benefit the development of a diluted magnetic semiconductor.

Crystal, magnetic and electronic structures and properties of new BaMnPnF (Pn = As, Sb, Bi)

New BaMnPnF (Pn = As, Sb, Bi) are synthesized by stoichiometric reaction of elements with BaF2. They crystallize in the P4/nmm space group, with the ZrCuSiAs-type structure, as indicated by X-ray crystallography. Electrical resistivity results indicate that Pn = As, Sb, and Bi are semiconductors with band gaps of 0.73 eV, 0.48 eV and 0.003 eV (extrinsic value), respectively. Powder neutron diffraction reveals a G-type antiferromagnetic order below TN = 338(1) K for Pn = As, and below TN = 272(1) K for Pn = Sb. Magnetic susceptibility increases with temperature above 100 K for all the materials. Density functional calculations find semiconducting antiferromagnetic compounds with strong in-plane and weaker out-of-plane exchange coupling that may result in non-Curie Weiss behavior above TN. The ordered magnetic moments are 3.65(5) μB/Mn for Pn = As, and 3.66(3) μB/Mn for Pn = Sb at 4 K, as refined from neutron diffraction experiments.

Synthesis and Superconductivity of New BiS2 Based Superconductor PrO0.5F0.5BiS2

We report synthesis and superconductivity at 3.7 K in PrO0.5F0.5BiS2. The newly discovered material belongs to the layered sulfide based REO0.5F0.5BiS2 compounds having a ZrCuSiAs-type structure. The bulk polycrystalline compound is synthesized by the vacuum encapsulation technique at 780 ∘C in a single step. Detailed structural analysis has shown that the as synthesized PrO0.5F0.5BiS2 is crystallized in a tetragonal P4/nmm space group with lattice parameters a=4.015(5) Å, c=13.362(4) Å. Bulk superconductivity is observed in PrO0.5F0.5BiS2 below 4 K from magnetic and transport measurements. Electrical transport measurements showed superconducting transition temperature (T c ) onset at 3.7 K and T c (ρ=0) at 3.1 K. The hump at T c related to the superconducting transition is not observed in the heat capacity measurement and rather a Schottky-type anomaly is observed at below ∼6 K. The compound is slightly semiconducting in a normal state. Isothermal magnetization (MH) exhibited typical type II behavior with a lower critical field (H c1) of around 8 Oe.

Layered Hydride CaNiGeH with a ZrCuSiAs-type Structure: Crystal Structure, Chemical Bonding, and Magnetism Induced by Mn Doping

Stimulated by the discovery of the iron oxypnictide superconductor with ZrCuSiAs-type structure in 2008, extensive exploration of its isostructural and isoelectronic compounds has started. These compounds, including oxides, fluorides, and hydrides, can all be simply recognized as valence compounds for which the octet rule is valid. We report herein the first example of a ZrCuSiAs-type hydride, CaNiGeH, which violates the octet rule. This hydride was synthesized by hydrogenation of the CeFeSi-type compound CaNiGe under pressurized hydrogen. Powder diffraction and theoretical simulation confirm that H enters into the interstitial position of the Ca(4) tetrahedron, leading to notable anisotropic expansion of the unit cell along the c axis. Density functional theory calculations indicate the modification of the chemical bonding and formation of ionic Ca-H bond as a result of hydrogen insertion. Furthermore, CaNiGeH shows Pauli paramagnetism and metallic conduction similar to that of CaNiGe, but its carrier type changes to hole and the carrier density is drastically reduced as compared to CaNiGe. Mn-doping at the Ni site introduces magnetism to both the parent compound and the hydride. The measurement demonstrates that hydrogenation of CaNi(1-x)Mn(x)Ge reduces ferromagnetic ordering of Mn ions and induces huge magnetic hysteresis, whereas the spin glass state observed for the parent compound is preserved in the hydride. The hydrogenation-induced changes in the electric and magnetic properties are interpreted in terms of development of two-dimensionality in crystal structure as well as electronic state.