Recent Progress of Multiferroicity and Magnetoelectric Effects in ABX3‐Type Perovskite Metal–Organic Frameworks

Wang, Jie; Xu, Xingliang; Li, Xing’ao

doi:10.1002/admi.202300123

Cited by 3 publications

(1 citation statement)

References 154 publications

(319 reference statements)

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“…The present record of piezoelectric response among metal-organics belongs to the hexagonal perovskite (TMFM) x (TMCM) 1−x CdCl 3 with d 33 = 1500 pC/N [1], but several molecular ferroelectrics have already been studied. Review articles on these materials have been published [2]; these studies focus on their piezoelectric properties and applications [3], but also on the broader perspective of hydrogen-bonded ferroelectrics [4] and metal-organic compounds [5,6], from the point of view of the multiferroic properties [7,8] and considering the possible applications [6,9].…”

Section: Introductionmentioning

confidence: 99%

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Cordero,

Craciun,

Imperatori

et al. 2023

Materials

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We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX3) (MDABCO)(NH4)I3, which has already been demonstrated to become ferroelectric below TC= 448 K. Both the dielectric permittivity measured in air on discs pressed from powder and the complex Young’s modulus measured on resonating bars in a vacuum show that the material starts to deteriorate with a loss of mass just above TC, introducing defects and markedly lowering TC. The elastic modulus softens by 50% when heating through the initial TC, contrary to usual ferroelectrics, which are stiffer in the paraelectric phase. This is indicative of improper ferroelectricity, in which the primary order parameter of the transition is not the electric polarization, but the orientational order of the MDABCO molecules. The degraded material presents thermally activated relaxation peaks in the elastic energy loss, whose intensities increase together with the decrease in TC. The peaks are much broader than pure Debye due to the general loss of crystallinity. This is also apparent from X-ray diffraction, but their relaxation times have parameters typical of point defects. It is argued that the major defects should be of the Schottky type, mainly due to the loss of (MDABCO)2+ and I−, leaving charge neutrality, and possibly (NH4)+ vacancies. The focus is on an anelastic relaxation process peaked around 200 K at ∼1 kHz, whose relaxation time follows the Arrhenius law with τ0 ∼ 10−13 s and E≃0.4 eV. This peak is attributed to I vacancies (VX) hopping around MDABCO vacancies (VA), and its intensity presents a peculiar dependence on the temperature and content of defects. The phenomenology is thoroughly discussed in terms of lattice disorder introduced by defects and partition of VX among sites that are far from and close to the cation vacancies. A method is proposed for calculating the relative concentrations of VX, that are untrapped, paired with VA or forming VX–VA–VX complexes.

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Section: Introductionmentioning

confidence: 99%

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Cordero,

Craciun,

Imperatori

et al. 2023

Materials

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Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6H perovskite Ba3HoRu2
Kushwaha,
Roy,
Kumar
et al. 2024
Phys. Rev. B
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0
0
0
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Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Cordero,

Craciun,

Imperatori

et al. 2023

Preprint

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We measured the anelastic, dielectric and structural properties of the metal-free molecular perovskite (ABX$_{3}$) (MDABCO)(NH$_{4}$)I$_{3}$, which has already been demonstrated to become ferroelectric below $T_{\text{C}}=$ 448~K. Both the dielectric permittivity measured in air on discs pressed from powder and the complex Young's modulus measured on resonating bars in vacuum show that the material starts deteriorating with loss of mass just above $T_{\text{C}}$, introducing defects and markedly lowering $T_{\text{C}}$. The elastic modulus softens of 50\% when heating through the initial $T_{\mathrm{C}}$, contrary to usual ferroelectrics, which are stiffer in the paraelectric phase. This suggests improper ferroelectricity, where the primary order parameter of the transition is not the electric polarization, but the orientational order of the MDABCO molecules. The degraded material presents thermally activated relaxation peaks in the elastic energy loss, whose intensities increase together with the decrease of ~$T_{\mathrm{C}}$. The peaks are much broader than pure Debye, due to the general loss of crystallinity, also apparent from X-ray diffraction, but their relaxation times have parameters typical of point defects. It is argued that the major defects should be of the Schottky type, mainly due to the loss of (MDABCO)$^{2+} $ and I$^{-}$, leaving charge neutrality, and possibly also (NH$_{4}$)$^{+}$ vacancies. The focus is on an anelastic relaxation process peaked around 200~K at $\sim 1$~kHz, whose relaxation time follows the Arrhenius law with $\tau $$_{0}$~$\sim $\ $10^{-13}$\ s and $E\simeq 0.4$~eV. This peak is attributed to I vacancies (V$_{\text{X}}$) hopping around MDABCO vacancies (V$_{\text{A}}$) and its intensity presents a peculiar dependence on temperature and content of defects. The phenomenology is thoroughly discussed in terms of lattice disorder introduced by defects and of partition of V$_{\text{X}}$ among sites that are far from and close to the cation vacancies. A method is proposed for calculating the relative concentrations of V$_{\text{X}}$, that are untrapped, paired with V$_{\text{A}}$ or forming V$_{\text{X}}$--V$_{\text{A}}$--V$_{\text{X}}$ complexes.

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Recent Progress of Multiferroicity and Magnetoelectric Effects in ABX₃‐Type Perovskite Metal–Organic Frameworks

Cited by 3 publications

References 154 publications

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6H perovskite Ba3HoRu2
Kushwaha,
Roy,
Kumar
et al. 2024
Phys. Rev. B
0
0
0
0
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Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (<span aria-describedby="tippy-27">MDABCO)(NH<sub>4</sub>)I<sub>3</sub>

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Recent Progress of Multiferroicity and Magnetoelectric Effects in ABX3‐Type Perovskite Metal–Organic Frameworks

Cited by 3 publications

References 154 publications

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (MDABCO)(NH4)I3

Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6H perovskite Ba3HoRu2Kushwaha, Roy, Kumar et al. 2024Phys. Rev. B0000View full textAdd to dashboardCite

Phase Transition and Point Defects in the Ferroelectric Molecular Perovskite (<span aria-describedby="tippy-27">MDABCO)(NH<sub>4</sub>)I<sub>3</sub>

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Recent Progress of Multiferroicity and Magnetoelectric Effects in ABX₃‐Type Perovskite Metal–Organic Frameworks

Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of the 6H perovskite Ba3HoRu2
Kushwaha,
Roy,
Kumar
et al. 2024
Phys. Rev. B
0
0
0
0
View full text Add to dashboard Cite