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Neutron powder diffraction study of the of the magnetic structure of EuZrO3

Authors
  • Avdeev, M
  • Brendan, KM
  • Kolodiazhny, T
Publication Date
Jan 13, 2014
Source
ANSTO Publications Online
Keywords
Language
English
License
Unknown
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Abstract

Divalent europium perovskite oxides with the chemical formula EuMO3 (M D Ti and Zr) are of considerable interest as a consequence of their diverse and often intriguing physical properties. There is increasing evidence that the large magnetic moments of the Eu2C ion, which stem from the halffilled 4 shell, can couple to electrical polarization of the softmode optical phonons, leading to fascinating properties in EuTiO3 [1–6]. Surprisingly, amagnetoelectric effect is observed in EuZrO3, albeit on a smaller scale, despite the absence of an analogous soft mode [7]. In agreement with experimental data, recent theoretical efforts indicate that the microscopic origin of the spin–lattice coupling in EuMO3 perovskites is driven by a nonzero hybridization between the Eu 4f and M nd electronic orbitals, which, in turn, depend on the degree of the oxygen octahedral rotations [8, 9]. EuTiO3 is isostructural with SrTiO3 at room temperature, and both have a simple cubic perovskite structure (space group Pm3m) with a lattice constant of 3:9 Å. As established in the early neutron diffraction study of McGuire et al [3], the localized 4f spins of the Eu2C ions .S D7=2/ in EuTiO3 show Gtype antiferromagnetic (AFM) ordering below 5.3 K; the spin of each Eu2C cation is opposite to that of all of its nearest neighbours. This magnetic structure was confirmed recently by Scagnoli et al [10]. Since the radii of the 4f orbitals are much smaller than those of the 5s or 5p orbitals, the Eu f bands are narrow and the N´eel temperature is low. It was recently reported that EuZrO3 is isostructural with SrZrO3 and that it adopts an orthorhombic perovskite structure in space group Pnma [11–14]. The Eu sites in EuZrO3 form a pseudo simple cubic lattice similar to that seen in EuTiO3, and it has been widely assumed that the Eu 4f spins would exhibit a Gtype AFM ordering below 4.1 K [9, 15]. It was not obvious, however, whether the Gtype AFM ordering survives under strong rotations of the oxygen octahedra reported for EuZrO3. In an effort to understand the microscopic origin of the magnetoelectric effect in EuMO3 perovskites, we have studied the magnetic structure of EuZrO3 using powder neutron diffraction. This paper provides experimental proof of a Gtype magnetic ground state of EuZrO3. © 2014 IOP Publishing Ltd.

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