2019/07/10 by N. S. Sangeetha, V. Smetana, Volodymyr Smetana +4 · 21 citations
Chemistry · Materials Science · Physics and Astronomy · #Antiferromagnetism #Chemistry #Condensed matter physics #Crystal structure #Crystallography #Heat capacity #Iron-based superconductors research #Magnetic field #Magnetization #Materials science #Neutron diffraction #Order (exchange) #Physics #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Tetragonal crystal system #Thermodynamics #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.100.094438
published in Physical review. B./Physical review. B 100(9) (American Physical Society) · 17 pages, 5 tables, 17 captioned figures
arxiv created 2019/07/10 · openalex created_date 2019/07/23 · openalex publication_date 2019/09/23 · arxiv updated 2019/10/02 · openalex updated_date 2026/08/05
The Eu+2 spins-7/2 in EuNi2As2 with the body-centered tetragonal ThCr2Si2 structure order antiferromagnetically below the N'eel temperature TN=15 K into a helical antiferromagnetic (AFM) structure with the helix axis aligned along the tetragonal c axis and the Eu ordered moments aligned ferromagnetically within the ab plane as previously reported from neutron diffraction measurements [T. Jin et al., Phys. Rev. B 99, 014425 (2019)]. Here we study the crystallographic, magnetic, thermal, and electronic transport properties of Bi-flux-grown single crystals using single-crystal x-ray diffraction, anisotropic magnetic susceptibility \ensuremathχ, isothermal magnetization M, heat capacity C_p, and electrical resistivity \ensuremathρ measurements versus applied magnetic field H and temperature T. Vacancies are found on the Ni sites corresponding to the composition EuNi1.95(1)As2. A good fit of the \ensuremathρ(T) data by the Bloch-Gr"uneisen theory for metals was obtained. The \ensuremathχab(T) data below TN are fitted well by molecular field theory (MFT), and the helix turn angle kd and the Eu-Eu Heisenberg exchange constants are extracted from the fit parameters. The kd value is in good agreement with the neutron-diffraction result. The magnetic contribution to the zero-field heat capacity below TN is also fitted by MFT. The isothermal in-plane magnetization Mab exhibits two metamagnetic transitions versus H, whereas Mc(T=2\phantom\rule0.28em0exK) is nearly linear up to H=14 T, both behaviors being consistent with MFT. The Mc(H,T),\ensuremathρ(Hc,T), and Cp(Hc,T) data yielded a Hc\text\ensuremath-T phase diagram separating the AFM and paramagnetic phases in good agreement with MFT. Anisotropic \ensuremathχ(T) literature data for the ThCr2Si2-type helical antiferromagnet EuRh2As2 were also fitted well by MFT. A comparison is made between the crystallographic and magnetic properties of ThCr2Si2-type EuM2Pn2 compounds with M=Fe, Co, Ni, Cu, or Rh, and Pn=P or As, where only ferromagnetic and c-axis helical AFM structures are found.