Phys. Rev. B 108, 014417 (2023) - Structure and magnetic properties of hausmannite $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$, metastable high-pressure marokite $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$, and defected $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Mn}}_{3}{\mathrm{O}}

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Structure and magnetic properties of hausmannite $α − {Mn}_{3} O_{4}$ , metastable high-pressure marokite $γ − {Mn}_{3} O_{4}$ , and defected $α − {Mn}_{3} O_{4}$

Björn Schwarz, Julian Hansen, Anna-Lena Hansen, Eugen Zemlyanushin, and Helmut Ehrenberg

Phys. Rev. B 108, 014417 – Published 13 July 2023

Abstract

The magnetic properties of tetragonal $α − {Mn}_{3} O_{4}$ spinel, its metastable high-pressure modification $γ − {Mn}_{3} O_{4}$ , and of an $α − {Mn}_{3} O_{4}$ modification with a high amount of lattice defects were investigated by direct current (dc) and alternating current (ac) magnetometry as well as by heat capacity measurements. An $α − {Mn}_{3} O_{4}$ phase modification with a high amount of lattice defects instead of the desired metastable high pressure $γ − {Mn}_{3} O_{4}$ phase might unintentionally be obtained after the high-pressure application. The obtained results clarify strongly contradictory reports about the dc susceptibility data of $γ − {Mn}_{3} O_{4}$ in the literature. Further, in situ low-temperature x-ray diffraction experiments from 150 to 275 K and Mn K-edge x-ray absorption spectroscopy experiments at 80 and 300 K do not indicate any structural transition to be coupled with the magnetic transition at 210 K for the given $γ − {Mn}_{3} O_{4}$ sample. This is in contradiction with what was concluded from powder neutron diffraction alone in the literature, where a coupled structural transition accompanied with large atomic displacements of a Mn species was claimed to be accompanied to the magnetic transition.

Received 6 February 2023
Revised 15 March 2023
Accepted 22 June 2023

DOI:https://doi.org/10.1103/PhysRevB.108.014417

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

High-pressure studies Magnetic order Magnetic phase transitions Magnetic susceptibility

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Björn Schwarz ^*, Julian Hansen , Anna-Lena Hansen , Eugen Zemlyanushin , and Helmut Ehrenberg

Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany

^*Corresponding author: bjoern.schwarz@kit.edu

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Vol. 108, Iss. 1 — 1 July 2023

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Figure 1
X-ray diffraction patterns with observed intensities (black crosses), simulated intensities (red line), difference between observed and simulated intensities (blue line), and positions of Bragg reflections (green ticks) for samples (a) spinel with Bragg reflections of $α − {Mn}_{3} O_{4}$ ( $I 4_{1} / a m d$ ), (b) def-spinel with Bragg reflections of $α − {Mn}_{3} O_{4}$ ( $I 4_{1} / a m d$ ), and (c) post-spinel with first row Bragg reflections of $γ − {Mn}_{3} O_{4}$ ( $P b c m$ ) and second row Bragg reflections of $α − {Mn}_{2} O_{3}$ ( $I a \bar{3}$ ).
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Figure 2
In situ low-temperature XRD of the post-spinel sample with $γ − {Mn}_{3} O_{4}$ as the main phase at (a) 275, (b) 250, (c) 225, (d) 200, (e) 175, and (f) 150 K. Observed intensities (black crosses), simulated intensities (red line), difference between observed and simulated intensities (blue line), and positions of Bragg reflections (green ticks) with first row Bragg reflections of $γ − {Mn}_{3} O_{4}$ ( $P b c m$ ), second row Bragg reflections of $α − {Mn}_{2} O_{3}$ ( $I a \bar{3}$ ), and third row Bragg reflections of water ice ( $P 6_{3} m c$ ).
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Figure 3
(a) Lattice parameters $a$ , $b$ , and $c$ and unit cell volume $V$ of $γ − {Mn}_{3} O_{4}$ main phase in dependence of temperature as obtained by Rietveld refinement of the respective structural models, based on in situ low temperature XRD data measured for the postspinel sample. See experimental section for explanation of vertical bars. (b) Sections of synchrotron Mn K-edge XAS spectra measured at 80 and 300 K for the post-spinel sample ( $γ − {Mn}_{3} O_{4}$ main phase) and for the $α − {Mn}_{3} O_{4}$ spinel sample.
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Figure 4
The dc susceptibility: (a) ZFC (black) and FC (red) susceptibility curves obtained for the spinel sample ( $α − {Mn}_{3} O_{4}$ ) at 500 Oe. (b) ZFC and FC susceptibility curves for various magnetic fields obtained for the post-spinel sample (mainly $γ − {Mn}_{3} O_{4}$ phase). (c) ZFC (black) and FC (red) susceptibility curves obtained for the def-spinel sample ( $α − {Mn}_{3} O_{4}$ with high amount of lattice defects) at 500 Oe. (d) Inverse susceptibility curves for all samples derived from ZFC curves measured at 500 Oe together with a Curie-Weiss fit from 370 to 390 K (solid line) and extrapolation (dashed line).
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Figure 5
The dc magnetometry: Field scans for the (a) spinel sample ( $α − {Mn}_{3} O_{4}$ ) together with zero-field extrapolation of magnetization at 20 K, (b) post-spinel sample (mainly $γ − {Mn}_{3} O_{4}$ phase) with the evolution of the magnetization at 70 kOe for various temperatures as extracted from field scans (inset at the right bottom), and (c) def-spinel sample ( $α − {Mn}_{3} O_{4}$ with high amount of defects). (d) Isothermal time-dependent change of magnetization for the spinel sample ( $α − {Mn}_{3} O_{4}$ phase) that was zero-field cooled from 100 K to the corresponding temperature before a dc field of 1000 Oe was applied. Double-logarithmic plot of $Δ M / M_{0}$ vs time of the isothermal evolution of magnetization at 10 and 20 K together with a time-dependent power-law fit (dashed lines).
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Figure 6
Real $χ^{'}$ (black) and imaginary $χ^{″}$ (red) part of the ac susceptibility with 0.1 (square), 1 (circle), and 10 kHz (triangle) excitation frequency for (a) the spinel sample ( $α − {Mn}_{3} O_{4}$ ), (b) for the post-spinel sample (mainly $γ − {Mn}_{3} O_{4}$ phase), only measured at 1 and 10 kHz, and (c) for the def-spinel sample ( $α − {Mn}_{3} O_{4}$ phase with high amount of lattice defects), only measured at 1 and 10 kHz. (d) Isobaric heat capacity vs temperature for the def-spinel sample at 0 and 30 kOe (3 T) and for the post-spinel sample at 0 kOe.
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Physical Review B

covering condensed matter and materials physics

Structure and magnetic properties of hausmannite $α − {Mn}_{3} O_{4}$ , metastable high-pressure marokite $γ − {Mn}_{3} O_{4}$ , and defected $α − {Mn}_{3} O_{4}$

Björn Schwarz, Julian Hansen, Anna-Lena Hansen, Eugen Zemlyanushin, and Helmut Ehrenberg

Phys. Rev. B 108, 014417 – Published 13 July 2023

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Physical Review B

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Structure and magnetic properties of hausmannite α−Mn3O4, metastable high-pressure marokite γ−Mn3O4, and defected α−Mn3O4

Björn Schwarz, Julian Hansen, Anna-Lena Hansen, Eugen Zemlyanushin, and Helmut Ehrenberg

Phys. Rev. B 108, 014417 – Published 13 July 2023

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Structure and magnetic properties of hausmannite $α − {Mn}_{3} O_{4}$ , metastable high-pressure marokite $γ − {Mn}_{3} O_{4}$ , and defected $α − {Mn}_{3} O_{4}$