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Hydration-induced spin-glass state in a frustrated Na-Mn-O triangular lattice

Hydration-induced spin-glass state in a frustrated Na-Mn-O triangular lattice
Hydration-induced spin-glass state in a frustrated Na-Mn-O triangular lattice
Birnessite compounds are stable across a wide range of compositions that produces a remarkable diversity in their physical, electrochemical, and functional properties. These are hydrated analogs of the magnetically frustrated, mixed-valent manganese oxide structures, with general formula, NaxMnO2. Here we demonstrate that the direct hydration of layered rock-salt type ?-NaMnO2, with the geometrically frustrated triangular lattice topology, yields the birnessite type oxide, Na0.36MnO2?0.2H2O, transforming its magnetic properties. This compound has a much-expanded interlayer spacing compared to its parent ?-NaMnO2 compound. We show that while the parent ?-NaMnO2 possesses a Néel temperature of 45 K as a result of broken symmetry in the Mn3+ sublattice, the hydrated derivative undergoes collective spin freezing at 29 K within the Mn3+/Mn4+ sublattice. Scaling-law analysis of the frequency dispersion of the ac susceptibility, as well as the temperature-dependent, low-field dc magnetization confirm a cooperative spin-glass state of strongly interacting spins. This is supported by complementary spectroscopic analysis [high-angle annular dark-field scanning transmission electron miscroscopy (TEM), energy-dispersive x-ray spectroscopy, and electron energy-loss spectroscopy] as well as by a structural investigation (high-resolution TEM, x-ray, and neutron powder diffraction) that yield insights into the chemical and atomic structure modifications. We conclude that the spin-glass state in birnessite is driven by the spin frustration imposed by the underlying triangular lattice topology that is further enhanced by the in-plane bond-disorder generated by the mixed-valent character of manganese in the layers.
1550-235X
1-10
Bakaimi, Ioanna
3c4e7000-517c-41fa-84db-c45641125e4d
Brescia, Rosaria
90bdf8f5-c7ba-430d-9f5f-5faf32dc2557
Brown, Craig M.
79d83564-75ad-40b6-8f07-4b7e79f3b8cc
Tsirlin, Alexander A.
27bb96ec-f059-49e3-917d-009bf6b3aff9
Green, Mark A.
82f1a0d9-e9b2-4557-9259-98ab93471721
Lappas, Alexandros
3e727545-5524-4bb7-a240-1c1aef2ce62d
Bakaimi, Ioanna
3c4e7000-517c-41fa-84db-c45641125e4d
Brescia, Rosaria
90bdf8f5-c7ba-430d-9f5f-5faf32dc2557
Brown, Craig M.
79d83564-75ad-40b6-8f07-4b7e79f3b8cc
Tsirlin, Alexander A.
27bb96ec-f059-49e3-917d-009bf6b3aff9
Green, Mark A.
82f1a0d9-e9b2-4557-9259-98ab93471721
Lappas, Alexandros
3e727545-5524-4bb7-a240-1c1aef2ce62d

Bakaimi, Ioanna, Brescia, Rosaria, Brown, Craig M., Tsirlin, Alexander A., Green, Mark A. and Lappas, Alexandros (2016) Hydration-induced spin-glass state in a frustrated Na-Mn-O triangular lattice. Physical Review B, 93 (184422), 1-10. (doi:10.1103/PhysRevB.93.184422).

Record type: Article

Abstract

Birnessite compounds are stable across a wide range of compositions that produces a remarkable diversity in their physical, electrochemical, and functional properties. These are hydrated analogs of the magnetically frustrated, mixed-valent manganese oxide structures, with general formula, NaxMnO2. Here we demonstrate that the direct hydration of layered rock-salt type ?-NaMnO2, with the geometrically frustrated triangular lattice topology, yields the birnessite type oxide, Na0.36MnO2?0.2H2O, transforming its magnetic properties. This compound has a much-expanded interlayer spacing compared to its parent ?-NaMnO2 compound. We show that while the parent ?-NaMnO2 possesses a Néel temperature of 45 K as a result of broken symmetry in the Mn3+ sublattice, the hydrated derivative undergoes collective spin freezing at 29 K within the Mn3+/Mn4+ sublattice. Scaling-law analysis of the frequency dispersion of the ac susceptibility, as well as the temperature-dependent, low-field dc magnetization confirm a cooperative spin-glass state of strongly interacting spins. This is supported by complementary spectroscopic analysis [high-angle annular dark-field scanning transmission electron miscroscopy (TEM), energy-dispersive x-ray spectroscopy, and electron energy-loss spectroscopy] as well as by a structural investigation (high-resolution TEM, x-ray, and neutron powder diffraction) that yield insights into the chemical and atomic structure modifications. We conclude that the spin-glass state in birnessite is driven by the spin frustration imposed by the underlying triangular lattice topology that is further enhanced by the in-plane bond-disorder generated by the mixed-valent character of manganese in the layers.

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PRB_Bakaimi_2016_1605.06067.pdf - Accepted Manuscript
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Accepted/In Press date: March 2016
e-pub ahead of print date: 18 May 2016
Organisations: Chemistry

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Local EPrints ID: 403339
URI: https://eprints.soton.ac.uk/id/eprint/403339
ISSN: 1550-235X
PURE UUID: 31b167e3-6cae-4004-b95d-bb51f0901749
ORCID for Ioanna Bakaimi: ORCID iD orcid.org/0000-0002-8083-4413

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Date deposited: 30 Nov 2016 10:30
Last modified: 14 Jul 2018 00:24

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Author: Ioanna Bakaimi ORCID iD
Author: Rosaria Brescia
Author: Craig M. Brown
Author: Alexander A. Tsirlin
Author: Mark A. Green
Author: Alexandros Lappas

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