Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo{2-y}As2

Abstract

The compound EuCo{2-y}As2 with the tetragonal ThCr2Si2 structure is known to contain Eu{+2} ions with spin S = 7/2 that order below a temperature TN = 47 K into an antiferromagnetic (AFM) proper helical structure with the ordered moments aligned in the tetragonal ab plane, perpendicular to the helix axis along the c axis, with no contribution from the Co atoms. Here we carry out a detailed investigation of the properties of single crystals. Enhanced ordered and effective moments of the Eu spins are found in most of our crystals. Electronic structure calculations indicate that the enhanced moments arise from polarization of the d bands, as occurs in ferromagnetic Gd metal. Electrical resistivity measurements indicate metallic behavior. The low-field in-plane magnetic susceptibilities chi{ab}(T < TN) for several crystals are reported that are fitted well by unified molecular field theory (MFT), and the Eu-Eu exchange interactions Jij are extracted from the fits. High-field magnetization M data for magnetic fields H||ab reveal what appears to be a first-order spin-flop transition followed at higher field by a second-order metamagnetic transition of unknown origin, and then by another second-order transition to the paramagnetic (PM) state. For H||c, the magnetization shows only a second-order transition from the canted AFM to the PM state, as expected. The critical fields for the AFM to PM transition are in approximate agreement with the predictions of MFT. Heat capacity Cp measurements in zero and high H are reported. Phase diagrams for H||c and H||ab versus T are constructed from the high-field M(H,T) and Cp(H,T) measurements. The magnetic part Cmag(T, H = 0) of Cp(T, H = 0) is extracted and is fitted rather well below TN by MFT, although dynamic short-range AFM order is apparent in Cmag(T) up to about 70 K, where the molar entropy attains its high-T limit of R ln8.

29 pages, 30 figures including 62 subfigures, 8 tables, 84 references

References in corpus (45)

• The Puzzle of High Temperature Superconductivity in Layered Iron Pnictides and Chalcogenides
• Superconductivity in Iron Compounds
• A Common Thread: the pairing interaction for the unconventional superconductors
• Nematic order in iron superconductors - who is in the driver's seat?
• Antiferromagnetic order and spin dynamics in iron-based superconductors
• High Temperature Superconductivity in Iron Pnictides and Chalcogenides
• Iron-Based Superconductors: current status of materials and pairing mechanism
• The Unexpected Properties of Alkali Metal Iron Selenide Superconductors
• The Unprecedented Giant Coupling of Fe-spin State and the As-As Hybridization in Iron-Pnictide
• Nature of the Magnetic Order in BaMn2As2
• Magnetic structure of EuFe2As2 determined by single crystal neutron diffraction
• Magnetic Exchange Interactions in BaMn2As2: A Case Study of the J1-J2-Jc Heisenberg Model
• Magnetic, Transport, and Thermal Properties of Single Crystals of the Layered Arsenide BaMn2As2
• Electronic structure and Magnetism in BaMn${}_2$As${}_2$ and BaMn${}_2$Sb${}_2$
• Frustrated Magnetic Interactions, Giant Magneto-Elastic Coupling, and Magnetic Phonons in Iron-Pnictides
• Structural, Thermal, Magnetic and Electronic Transport Properties of the LaNi2(Ge{1-x}P{x})2 System
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Unified Molecular Field Theory for Collinear and Noncollinear Heisenberg Antiferromagnets
• Magnetic Susceptibility of Collinear and Noncollinear Heisenberg Antiferromagnets
• Magnetic Dipole Interactions in Crystals
• Crystallographic, Electronic, Thermal and Magnetic Properties of Single-Crystal SrCo2As2
• Crystal Growth and Physical Properties of SrCu2As2, SrCu2Sb2 and BaCu2Sb2
• Itinerant antiferromagnetism in BaCr${}_2$As${}_2$
• Crystal and Magnetic Structure of CaCo{1.86}As2 Studied by X-ray and Neutron Diffraction
• Itinerant and local-moment magnetism in EuCr2As2 single crystals
• Antiferromagnetism in EuCu2As2 and EuCu1.82Sb2 Single Crystals
• Physical Properties of Metallic Antiferromagnetic CaCo{1.86}As2 Single Crystals
• EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet
• Antiferromagnetic structure and electronic properties of BaCr2As2 and BaCrFeAs2
• Magnetic structure and spin excitations in BaMn2Bi2
• Antiferromagnetism in trigonal SrMn2As2 and CaMn2As2 single crystals
• Influence of uniaxial single-ion anisotropy on the magnetic and thermal properties of Heisenberg antiferromagnets within unified molecular field theory
• Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals
• Crystallography and Physical Properties of BaCo2As2, Ba{0.94}K{0.06}Co2As2 and Ba{0.78}K{0.22}Co2As2
• Formation of Collapsed Tetragonal Phase in EuCo2As2 under High Pressure
• ARPES observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn${}_2$As${}_2$ and BaMn${}_2$Sb${}_2$
• Pressure-induced collapsed-tetragonal phase in SrCo2As2
• Observation of a remarkable reduction of correlation effects in BaCr2As2 by ARPES
• Collinear antiferromagnetism in trigonal SrMn${}_2$As${}_2$ revealed by single-crystal neutron diffraction
• Optical properties of the iron-pnictide analog BaMn2As2
• Is BaCr${}_2$As${}_2$ symmetrical to BaFe${}_2$As${}_2$ with respect to half $3d$ shell filling?
• Structure and magnetic, thermal, and electronic transport properties of single crystal EuPd2Sb2
• EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet
• Influence of classical anisotropy fields on the properties of Heisenberg antiferromagnets within unified molecular field theory
• Coexistence of antiferromagnetic and ferromagnetic spin correlations in SrCo2As2 revealed by 59Co and 75As NMR

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• Instability and evolution of the magnetic ground state in metallic perovskites GdRh${}_3$C${}_{1-x}$B${}_x$
• Electronic structure of $A$Co${}_2$As${}_2$ ($A=$ Ca, Sr, Ba, Eu) studied using angle-resolved photoemission spectroscopy and theoretical calculations
• Europium $c$-axis ferromagnetism in Eu(Co${}_{1-x}$Ni${}_x$)${}_{2-y}$As${}_2$: A single-crystal neutron diffraction study
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• Multiple magnetic orders discovered in the superconducting state of EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$