Crystallography and Magnetic Phenomena

Kopský, V.

doi:10.3390/sym7010125

Cited by 7 publications

(3 citation statements)

References 23 publications

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“…The magnetic point group of the normal state is O h ⊗ {1, T }, where T denotes time reversal. Since {1, T } appears as a factor group, the magnetic point group is "gray" [33,34]. The Hermann-Mauguin notation is m 3m1 , where 1 stands for time reversal combined with the spatial identity operation [33].…”

Section: Model Systemmentioning

confidence: 99%

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

2021

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Centrosymmetric multiband superconductors which break time-reversal symmetry generically have two-dimensional nodes, i.e., Fermi surfaces of Bogoliubov quasiparticles. We show that the coupling of the electrons to the lattice always leads to a weak-coupling instability of such a state towards spontaneous breaking of inversion symmetry at low temperatures. This instability is driven by a Cooper logarithm in the internal energy but the order parameter is not superconducting but distortional. We present a comprehensive symmetry analysis and introduce a measure that allows to compare the strengths of competing distortional instabilities. Moreover, we discuss the instability using an effective single-band model. This framework reveals a duality mapping of the effective model which maps the distortional order parameter onto a superconducting one, providing a natural explanation for the Cooper logarithm and the weak-coupling nature of the instability. Finally, we consider the possibility of a pair-density wave state when inversion symmetry is broken. We find that it can indeed exist but does not affect the instability itself.

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Section: Model Systemmentioning

confidence: 99%

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

2021

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“…While the significance of raising T N by nearly 75 K via delithiation can be readily appreciated, the relevance of also changing the magnetic point symmetry may not be immediately apparent. The magnetic point group for a material has implications for the type of allowed magnetic properties. − In the case of the olivine phosphates, it is the magnetoelectric properties that are of primary importance to us. ,,,, Mercier demonstrated that all the olivines for M = Mn, Fe, Co, and Ni display magnetoelectric properties whereby the magnetization is related to an externally applied electric field E via the magnetoelectric tensor α (given by ) . Furthermore, LiCoPO 4 was found to display a special type of magnetoelectricity known as ferrotoroidicity. , This latter property completes the table of the three known primary ferroicsferromagnetism, ferroelectricity, and ferroelasticity (Figure b–d). − The fourth ferroic, ferrotoroidicity (Figure a), is the result of toroidal moments ordering spontaneously upon cooling below a certain temperature.…”

Section: Introductionmentioning

confidence: 99%

Tuning Magnetic Symmetry and Properties in the Olivine Series Li_1–xFe_xMn_1–xPO₄ through Selective Delithiation

et al. 2022

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We present the first in-depth study of the nuclear and magnetic structures of the fully lithiated LiFe x Mn 1−x PO 4 solid solutions as well as the partially delithiated Li 1−x Fe x Mn 1−x PO 4 series using neutron powder diffraction. By using a weak oxidizing solution that only oxidizes Fe 2+ , we find that lithium can be removed from these olivines in a stepwise manner. Representational analysis was performed on the observed magnetic reflections and found that the lithiated solid solutions order in the magnetic space group Pnma′, which is identical to triphylite (LiFePO 4 ). We report that, even when removing 20% of the lithium from the hcp lattice, the magnetic structure changes and multiple magnetic contributions are needed to fully encompass the observed magnetic order. We find that the partially delithiated x = 0.2 and 0.3 have a magnetic structure P2 1 ′/n11, and when x surpasses 0.3, the magnetic structure changes to P2 1 2 1 2 1 . We give a detailed report on the effect of delithiation on magnetic order, bond distances/angles, and the super-and supersuperexchange interactions in the material. The symmetries of the magnetic order of these solid solutions are then discussed with regard to their potential as ferrotoroidic candidates.

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“…For more details and forms of tensors, we refer to the reviews in Refs. [15,[20][21][22], and the original works in Refs. [16,18,19,23,24].…”

Section: Introductionmentioning

confidence: 99%

Quadratic magnetoelectric effect during field cooling in sputter grown Cr$_2$O$_3$ films

Al-Mahdawi,

Nozaki,

Oogane

et al. 2021

Preprint

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Cr2O3 is the archetypal magnetoelectric (ME) material, which has a linear coupling between electric and magnetic polarizations. Quadratic ME effects are forbidden for the magnetic point group of Cr2O3, due to space-time inversion symmetry. In Cr2O3 films grown by sputtering, we find a signature of a quadratic ME effect that is not found in bulk single crystals. We use Raman spectroscopy and magetization measurements to deduce the removal of space-time symmetry, and corroborate the emergence of the quadratic ME effect. We propose that meta-stable site-selective trace dopants remove the space, time, and space-time inversion symmetries from the original magnetic point group of bulk Cr2O3. We include the quadratic ME effect in a model describing the switching process during ME field cooling, and estimate the effective quadratic susceptibility value. The quadratic magnetoelectric effect in a uniaxial antiferromagnet is promising for multifunctional antiferromagnetic and magnetoelectric devices that can incorporate optical, strain-induced, and multiferroic effects.

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Crystallography and Magnetic Phenomena

Cited by 7 publications

References 23 publications

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

Tuning Magnetic Symmetry and Properties in the Olivine Series Li_1–xFe_xMn_1–xPO₄ through Selective Delithiation

Quadratic magnetoelectric effect during field cooling in sputter grown Cr$_2$O$_3$ films

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Crystallography and Magnetic Phenomena

Cited by 7 publications

References 23 publications

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

Distortional weak-coupling instability of Bogoliubov Fermi surfaces

Tuning Magnetic Symmetry and Properties in the Olivine Series Li1–xFexMn1–xPO4 through Selective Delithiation

Quadratic magnetoelectric effect during field cooling in sputter grown Cr$_2$O$_3$ films

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Tuning Magnetic Symmetry and Properties in the Olivine Series Li_1–xFe_xMn_1–xPO₄ through Selective Delithiation