Effects of 4d transition metal Pd doping on the magnetic and superconducting properties of 112-type iron pnictide EuFeAs2

2021 ◽  
Author(s):  
Xinhui Zhan ◽  
Xiaolei Yi ◽  
Xiangzhuo Xing ◽  
Meng Li ◽  
Linchao Yu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Electrical Transport ◽  
Parent Phase ◽  
Density Wave ◽  
Spin Density Wave ◽  
Spin Reorientation ◽  
Iron Pnictide ◽  
Pd Doping ◽  
Reentrant Spin Glass ◽  
The Eu

Abstract The recently discovered 112-type EuFeAs2 compound that shows complex Eu-spin magnetism provides a new platform to study the interplay between superconductivity (SC) and magnetism in iron pnictide superconductors. In this paper, by substituting Fe with the 4d transition metal Pd, we have successfully synthesized a series of EuFe1-xPdxAs2 (0 ≤ x ≤ 0.08) samples and studied the doping effect on SC and magnetism by means of electrical transport and magnetization measurements. The systematic evolution of the lattice parameters indicates that the Pd atoms have been successfully substituted into the Fe sites. With Pd doping, the Fe-related spin density wave (SDW) transition at TFe m in the parent phase is rapidly suppressed, and SC simultaneously emerges, exhibiting a domelike shape with a maximum onset transition temperature Tonset c of around 18.5 K at x = 0.04. On the other hand, the Eu-related AFM order at TEu m is suppressed very slowly and persists up to x = 0.08, covering the whole SC dome region. Also, the reentrant spin-glass and spin-reorientation transitions below TEu m remain unchanged with Pd doping. All these results indicate that the Eu spins have little effect on SC in EuFe1-xPdxAs2. Finally, based on the resistivity and magnetization data, the T-x phase diagram of EuFe1-xPdxAs2 is constructed and compared with those of 3d transition metals Co/Ni and La doped ones.

scholarly journals 57Fe and 151Eu Mössbauer studies of 3d-4f spin interplay in EuFe2−xNixAs2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
K. Komędera ◽  
J. Gatlik ◽  
A. Błachowski ◽  
J. Żukrowski ◽  
D. Rybicki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Order ◽  
Parent Compound ◽  
Density Wave ◽  
Hyperfine Magnetic Field ◽  
Spin Density Wave ◽  
Spin Reorientation ◽  
Substitution Level ◽  
Ni Substitution ◽  
The Eu

AbstractThe EuFe2−xNixAs2 (with 0 ≤ x ≤ 0.4) compounds exhibiting 3d and/or 4f magnetic order were investigated by means of 57Fe and 151Eu Mössbauer spectroscopy. Additionally, results for EuNi2As2 are reported for comparison. It was found that spin-density-wave order of the Fe itinerant moments is monotonically suppressed by Ni-substitution. However, the 3d magnetic order survives at the lowest temperature up to at least x = 0.12 and it is certainly completely suppressed for x = 0.20. The Eu localized moments order regardless of the Ni concentration, but undergo a spin reorientation with increasing x from alignment parallel to the a-axis in the parent compound, toward c-axis alignment for x > 0.07. Change of the 4f spins ordering from antiferromagnetic to ferromagnetic takes place simultaneously with a disappearance of the 3d spins order what is the evidence of a strong coupling between magnetism of Eu2+ ions and the conduction electrons of [Fe2−xNixAs2]2- layers. The Fe nuclei experience the transferred hyperfine magnetic field due to the Eu2+ ordering for Ni-substituted samples with x > 0.04, while the transferred field is undetectable in EuFe2As2 and for compound with a low Ni-substitution level. It seems that the 4f ferromagnetic component arising from a tilt of the Eu2+ moments to the crystallographic c-axis leads to the transferred magnetic field at the Fe atoms. Superconductivity is not observed down to 1.8 K, although a comparison with 57Fe and 151Eu Mössbauer data for EuFe2As2-based superconductors indicates a similar magnetic structure.

scholarly journals 57Fe and 151Eu Mössbauer Studies of 3d-4f Spin Interplay in EuFe2-xNixAs2

2021 ◽  
Author(s):  
K. Komędera ◽  
J. Gatlik ◽  
A. Błachowski ◽  
J. Żukrowski ◽  
D. Rybicki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Order ◽  
Parent Compound ◽  
Density Wave ◽  
Hyperfine Magnetic Field ◽  
Spin Density Wave ◽  
Spin Reorientation ◽  
Substitution Level ◽  
Ni Substitution ◽  
The Eu

Abstract The EuFe2-xNixAs2 compounds exhibiting 3d and/or 4f magnetic order were investigated by means of 57Fe and 151Eu Mössbauer spectroscopy. Additionally, results for the end members of this system, i.e. EuFe2As2 and EuNi2As2, are reported for comparison. It was found that spin-density-wave order of the Fe itinerant moments is monotonically suppressed by Ni-substitution. However, the 3d magnetic order survives at the lowest temperature up to at least x = 0.12 and it is certainly completely suppressed for x = 0.20. The Eu localized moments order regardless of the Ni concentration, but undergo a spin reorientation with increasing x from the alignment parallel to the a-axis in the parent compound, toward c-axis alignment for x > 0.07. The change of the 4f spins ordering from antiferromagnetic to ferromagnetic takes place simultaneously with a disappearance of the 3d spins order what is the evidence of a strong coupling between magnetism of Eu2+ ions and the conduction electrons of [Fe2-xNixAs2]2- layers. The Fe nuclei experience the transferred hyperfine magnetic field due to the Eu2+ ordering for Ni-substituted samples with x > 0.04, while the transferred field is undetectable in EuFe2As2 and for compound with a low Ni-substitution level. It seems that the 4f ferromagnetic component arising from a tilt of the Eu2+ moments to the crystallographic c-axis leads to the transferred magnetic field at the Fe atoms. The superconductivity is not observed down to 1.8 K, although a comparison with 57Fe and 151Eu Mössbauer data for EuFe2As2-based superconductors indicates a similar magnetic structure.

scholarly journals Reemergence of superconductivity by 4d transition-metal Pd doping in over-doped 112-type iron pnictide superconductors Ca0.755La0.245FeAs2

2019 ◽  
Vol 21 (9) ◽  
pp. 093015 ◽  
Author(s):  
Xiangzhuo Xing ◽  
Zhanfeng Li ◽  
Ivan Veshchunov ◽  
Xiaolei Yi ◽  
Yan Meng ◽  
...  
Keyword(s):  
Transition Metal ◽  
Iron Pnictide ◽  
Pnictide Superconductors ◽  
Pd Doping

scholarly journals Structural and Transport Properties of 1T-VSe2 Single Crystal Under High Pressures

2021 ◽  
Vol 8 ◽  
Author(s):  
Dongqi Song ◽  
Ying Zhou ◽  
Min Zhang ◽  
Xinyi He ◽  
Xinjian Li
Keyword(s):  
Transition Metal ◽  
Transport Properties ◽  
Electrical Transport ◽  
Critical Pressure ◽  
High Pressures ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Density Wave ◽  
Transition Metal Dichalcogenides ◽  
Transition Metal Dichalcogenide

Two-dimensional transition metal dichalcogenide 1T-VSe2 exhibits a unique three-dimensional charge density wave (CDW) order below ∼110 K at ambient pressure, which shows unusual evolution under pressure. Here we report on the high-pressure structural and transport properties of 1T-VSe2 by extending the pressure up to 57.8 GPa, through electrical transport, synchrotron X-ray diffraction (XRD) and Raman scattering measurements, which unravel two critical pressure points. The CDW transition is found to be enhanced under compression at a rate of 16.5 K/GPa up to the first critical pressure PC1 ∼ 12 GPa, at which a structural phase transition from hexagonal P-3m1 to monoclinic C2/m phase takes place. The second critical pressure PC2 ∼ 33 GPa corresponds to another structural transition from monoclinic C2/m to P21/m phase. These findings extend the phase diagram of pressurized 1T-VSe2 and may help to understand pressure tuning of structures in transition metal dichalcogenides.

Bond-Length Fluctuations in the Copper-Oxide Superconductors

2001 ◽  
Vol 689 ◽  
Author(s):  
John B. Goodenough
Keyword(s):  
Phase Diagram ◽  
Heavy Fermions ◽  
Parent Phase ◽  
Density Wave ◽  
Spin Density Wave ◽  
Phase Segregation ◽  
Itinerant Electron ◽  
Oxide Superconductors ◽  
Local Fluctuations ◽  
Superconductive Phase

ABSTRACTThe phase diagram of La2-xSrxCuO4 is interpreted. From the virial theorem, it is argued that the cross-over from localized to itinerant electronic behavior in the range 0 < x < 0.3 is characterized by fluctuations between two equilibrium Cu-O bond lengths. Cooperative local fluctuations give rise to one-hole correlation bags of 5 to 6 copper centers on the underdoped side, to strong-correlation fluctuations in an itinerant-electron matrix on the overdoped side. Spinodal phase segregation between an antiferromagnetic, insulating parent phase and the superconductive phase occurs in the underdoped compositions, between the superconductive phase and the metallic overdoped phase on the other side of the phase diagram. Ordering of the fluctuations into a travelling bipolaronic charge-density/spin-density wave of composition x ≈?1/6 yields heavy fermions of symmetry (x2− y2) coexisting with light electrons; the high-temperature superconductive pairs are condensed out from the heavy fermions.

scholarly journals 1D metallic states at 2D transition metal dichalcogenide semiconductor heterojunctions

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Sridevi Krishnamurthi ◽  
Geert Brocks
Keyword(s):  
Transition Metal ◽  
Density Wave ◽  
Transition Metal Dichalcogenides ◽  
Spin Density Wave ◽  
Electric Polarization ◽  
Transition Metal Dichalcogenide ◽  
First Principles Calculations ◽  
One Dimensional ◽  
Structural Details ◽  
Metal Dichalcogenides

AbstractTwo-dimensional (2D) lateral heterojunctions between different transition metal dichalcogenides (TMDCs) have been realized in recent years. Homogeneous semiconducting TMDC layers are characterized by a topological invariant, their in-plane electric polarization. It suggests the possibility of one-dimensional (1D) metallic states at heterojunctions where the value of the invariant changes. We study such lateral 2D TMDC junctions by means of first-principles calculations and show that 1D metallic states emerge even in cases where the different materials are joined epitaxially. We find that the metallicity does not depend on structural details, but, as the invariant is protected by spatial symmetry only, it can be upset by breaking the symmetry. Indeed, 1D charge- and spin-density wave instabilities appear spontaneously, making 2D TMDC heterojunctions ideal systems for studying 1D systems.

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