Abstract
This paper reports evidence that the antiferromagnetic and insulating ground state of MnO is caused by a nonadiabatic atomic-like motion, as is evidently the case in NiO. In addition, it is shown that experimental findings on the displacements of the Mn and O atoms in the antiferromagnetic phase of MnO corroborate the presented suggestion that the rhombohedral-like distortion in antiferromagnetic MnO, as well as in antiferromagnetic NiO is an inner distortion of the monoclinic base-centered Bravais lattice of the antiferromagnetic phases.
Highlights
The isomorphic transition-metal monoxides MnO and NiO are antiferromagnetic with the Néel temperatures TN = 122 K and TN = 523 K, respectively
The strongly correlated nonadiabatic atomic-like motion defined within the nonadiabatic Heisenberg model (NHM) [13] was not yet taken into consideration
The paper is concerned with three striking features of MnO: (i) The insulating ground state of both paramagnetic and antiferromagnetic MnO, (ii) the stability of the antiferromagnetic state, (iii) the rhombohedral-like deformation in the antiferromagnetic phase, characterizing likewise the isomorphic transition-metal monoxide NiO
Summary
TN , both monoxides possess f the fcc structure Fm3m = Γc Oh5 (225) (in parentheses, the international number), and below TN , the antiferromagnetic structure in both materials is invariant under the monoclinic base-centered magnetic group Cc 2/c given in Equation (1) [1,2,3,4]. In both MnO and NiO, the antiferromagnetic state is accompanied by a small rhombohedral-like [5] contraction of the crystal. The strongly correlated nonadiabatic atomic-like motion defined within the nonadiabatic Heisenberg model (NHM) [13] was not yet taken into consideration
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