Low-temperature crystal and magnetic structures of the magnetoelectric material Fe4Nb2O9 Articles uri icon

authors

  • JANA, RAJESH
  • SHEPTYAKOV, DENIS
  • MA, XIAOYAN
  • ALONSO, JOSE A.
  • PI, MAOCAI
  • MUĂ‘OZ CASTELLANOS, ANGEL
  • LIU, ZIYI
  • ZHAO, LINLIN
  • SU, NA
  • JIN, SHIFENG
  • MA, XIAOBAI
  • SUN, KAI
  • CHEN, DONGFENG
  • DONG, SHUAI
  • CHAI, YISHENG
  • LI, SHILIANG
  • CHENG, JINGUANG

publication date

  • September 2019

start page

  • 1

end page

  • 8

issue

  • 9

volume

  • 100

International Standard Serial Number (ISSN)

  • 1098-0121

Electronic International Standard Serial Number (EISSN)

  • 1550-235X

abstract

  • Fe4Nb2O9 was recently reported to be a new magnetoelectric material with two distinct dielectric anomalies located at TN ≈90K for an antiferromagnetic transition and Tstr ≈77K of unknown origin, respectively. By analyzing low-temperature neutron-powder-diffraction data, here we determined its magnetic structure below TN and uncovered the origin of the second dielectric anomaly as a structural phase transition across Tstr. In the antiferromagnetically ordered state below TN, both Fe1 and Fe2 magnetic moments lying within the weakly and strongly buckled honeycomb layers are arranged in a fashion that the three nearest neighbors are directed oppositely. Upon cooling below Tstr, the symmetry of crystal structure is lowered from trigonal P-3c1 to monoclinic C2/c, in which a weak sliding of the metal octahedral planes introduces a monoclinic distortion of ∼1.7◦. The magnetic structure is preserved in the low-temperature monoclinic phase, and the Fe magnetic moment increases from 2.1(1)muB at 95 K to 3.83(4)muB at 10 K assuming an equal moment configuration at Fe1 and Fe2 sites. The magnetic point group and linear magnetoelectric tensor at each temperature region are determined. From a symmetry-related tensor analysis, the microscopic origins of the magnetoelectric effects between TN and Tstr are proved to be spin-current and d-p hybridization mechanisms.

keywords

  • magnetic order; magneto-dielectric effect; antiferromagnets; multiferroics; crystal structures; neutron diffraction