EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet

Abstract

The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins 7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN = 66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab-plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility chi, high-field magnetization and magnetic heat capacity of EuCo2P2 single crystals at temperature T < TN with the predictions of our recent formulation of molecular field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~ T^3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the ab-plane and AFM interactions between nearest- and next-nearest planes, in agreement with the MFT analysis of chi{ab}(T < TN).

arXiv comment20 pages, 17 figures, 3 tables, 46 references. This is an extended replacement of arXiv:1512.02958 with an additional coauthor

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• Magnetic Structure and Magnetization of Helical Antiferromagnets in High Magnetic Fields Perpendicular to the Helix Axis at Zero Temperature
• Non-Fermi-liquid behaviors associated with a magnetic quantum-critical point in Sr(Co{1-x}Ni{x})2As2 single crystals
• Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals
• A-type antiferromagnetic order and magnetic phase diagram of the trigonal Eu spin-7/2 triangular-lattice compound EuSn2As2
• Enhanced moments of Eu in single crystals of the metallic helical antiferromagnet EuCo{2-y}As2
• A-type antiferromagnetic order in semiconducting EuMg${}_2$Sb${}_2$ single crystals
• Zero-field magnetic ground state of EuMg${}_2$Bi${}_2$
• NMR Determination of an Incommensurate Helical Antiferromagnetic Structure in EuCo2As2
• Helical Antiferromagnetic Ordering in EuNi{1.95}As2
• Flat band magnetism and helical magnetic order in Ni-doped SrCo${}_2$As${}_2$
• Magnetic phase transitions in Eu(Co,Ni)2As2 single crystals
• Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca{1-x}Sr{x}Co{2-y}As{2}
• NMR studies of the incommensurate helical antiferromagnet EuCo2P2 : determination of the antiferromagnetic propagation vector
• Large magnetoresistance and first-order phase transition in antiferromagnetic single-crystalline EuAg${}_4$Sb${}_2$
• Evidences for magnetic dimers and skyrmion lattice formation in Eu${}_2$Pd${}_2$Sn
• Influence of classical anisotropy fields on the properties of Heisenberg antiferromagnets within unified molecular field theory
• Molecular-field-theory fits to magnetic susceptibilities of antiferromagnetic GdCu2Si2, CuO, LiCrO2, and alpha-CaCr2O4 single crystals below their Neel temperatures
• Phenomenological theory of magnetic 90${}^{\circ }$ helical state
• Emergence of ferromagnetism due to Ir substitutions in single-crystalline Ba[Co(1 x)Ir(x)]2As2
• EPR measurements of Eu{+2} spins in metallic EuCo{2-y}As2 single crystals