Local disorder and structure relation induced by magnetic exchange interactions in A2(Mo1-yMny)2O7 pyrochlores Articles uri icon

authors

  • Castellano, C.
  • Scavini, M.
  • Berti, G.
  • Rubio Marcos, F.
  • Lamura, G.
  • Sanna, S.
  • SALAS COLERA, EDUARDO
  • Muñoz Noval, N.
  • Cimberle, M. R.
  • Demartin, F.

publication date

  • February 2021

start page

  • 1

end page

  • 14

volume

  • 865

International Standard Serial Number (ISSN)

  • 0925-8388

Electronic International Standard Serial Number (EISSN)

  • 1873-4669

abstract

  • We present an extended X-ray absorption fine structure study at the Mo K-edge of A2(Mo1−yMny)2O7
    (A = Gd, Ho; y = 0.05 and 0.10) pyrochlores, as a function of temperature and composition, coupled to
    diffractometric and magnetic characterizations. Extending the study reported in our previous paper on the
    pristine A2Mo2O7 compounds to these Mo/Mn partially substituted samples, where we hypothesize a
    competition between double-exchange and superexchange couplings, we aim to check which structure
    parameters are related to the nature of the nearest-neighbor magnetic interactions, looking for the presence
    and evolution of order and structure anomalies. Two Ho samples Ho2(Mo1−yMny)2O7 (y = 0.05 and 0.10)
    keep the spin-glass nature of the parent compositions with a strong distortion of the MoO(1)6 octahedron
    and of the Mo‒Ho and Mo‒Mo second shell. On the other hand, two Gd2(Mo1−yMny)2O7 samples, ferro-
    magnetic at low temperature in the undoped case, show the appearance on a local scale of a spin-glass
    transition mirrored by a quite high structure disorder and by a distortion coherent with a lattice frustration
    after Mn-doping. Therefore, the Gd and Ho Mn-doped samples display a similar frustrated behavior, dif-
    ferently from the corresponding undoped ones.

keywords

  • a. oxide materials; c. exchange and superexchange; c. order-disorder effects; d. exafs; d. x-ray diffraction