A2+ Cation Control of Chiral Domain Formation in A(TiO)Cu4(PO4)4 (A = Ba, Sr)

Kimura, Kazuhiro; Sera, M.; Kimura, Tsuyoshi

doi:10.1021/acs.inorgchem.5b02622

Cited by 28 publications

(63 citation statements)

References 23 publications

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“…[14] The initial structural parameters for this purpose were taken from Ref. [1]. Figure 2 shows the powder XRD patterns at 300 K and 15 K along with the fits.…”

Section: A Crystal Structurementioning

confidence: 99%

Frustration of square cupola in Sr(TiO) Cu4(PO4)4

Islam

Ranjith²,

Baenitz³

et al. 2018

Phys. Rev. B

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The structural and magnetic properties of the square-cupola antiferromagnet Sr(TiO)Cu4(PO4)4 are investigated via x-ray diffraction, magnetization, heat capacity, and 31 P nuclear magnetic resonance experiments on polycrystalline samples, as well as density-functional band-structure calculations. The temperature-dependent unit cell volume could be described well using the Debye approximation with the Debye temperature of θD 550 K. Magnetic response reveals a pronounced two-dimensionality with a magnetic long-range-order below TN 6.2 K. High-field magnetization exhibits a kink at 1/3 of the saturation magnetization. Asymmetric 31 P NMR spectra clearly suggest strong in-plane anisotropy in the magnetic susceptibility, as anticipated from the crystal structure. From the 31 P NMR shift vs bulk susceptibility plot, the isotropic and axial parts of the hyperfine coupling between 31 P nuclei and the Cu 2+ spins are calculated to be A iso hf 6539 and A ax hf 952 Oe/µB, respectively. The low-temperature and low-field 31 P NMR spectra indicate a commensurate antiferromagnetic ordering. Frustrated nature of the compound is inferred from the temperature-dependent 31 P NMR spin-lattice relaxation rate and confirmed by our microscopic analysis that reveals strong frustration of the square cupola by next-nearest-neighbor exchange couplings.

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“…[14] The initial structural parameters for this purpose were taken from Ref. [1]. Figure 2 shows the powder XRD patterns at 300 K and 15 K along with the fits.…”

Section: A Crystal Structurementioning

confidence: 99%

Frustration of square cupola in Sr(TiO) Cu4(PO4)4

Islam

Ranjith²,

Baenitz³

et al. 2018

Phys. Rev. B

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“…The asymmetric interactions lead to intriguing magnetism, e.g., weak ferromagnetism in antiferromagnets and spin-spiral ordering in helimagnets. They have also attracted growing interest as an origin of the magnetoelectric (ME) effect, that is, cross correlations between dielectricity and magnetism [3,4].Recently, an interesting series of chiral antiferromagnets, A(TiO)Cu 4 (PO 4 ) 4 (A = Ba, Sr) with space group P 42 1 2, was newly synthesized [5]. The materials have a quasi-two-dimensional structure, composed of an alternating array of Cu 4 O 12 clusters, as shown in Fig.…”

mentioning

confidence: 99%

“…Recently, an interesting series of chiral antiferromagnets, A(TiO)Cu 4 (PO 4 ) 4 (A = Ba, Sr) with space group P 42 1 2, was newly synthesized [5]. The materials have a quasi-two-dimensional structure, composed of an alternating array of Cu 4 O 12 clusters, as shown in Fig.…”

mentioning

confidence: 99%

Magnetoelectric Behavior from S=1/2 Asymmetric Square Cupolas

et al. 2017

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Magnetoelectric properties are studied by a combined experimental and theoretical study of a quasi-two-dimensional material composed of square cupolas, Ba(TiO)Cu4(PO4)4. The magnetization is measured up to above the saturation field, and several anomalies are observed depending on the field directions. We propose a S=1/2 spin model with Dzyaloshinskii-Moriya interactions, which well reproduces the full magnetization curves. Elaborating the phase diagram of the model, we show that the anomalies are explained by magnetoelectric phase transitions. Our theory also accounts for the scaling of the dielectric anomaly observed in experiments. The results elucidate the crucial role of the in-plane component of Dzyaloshinskii-Moriya interactions, which is induced by the noncoplanar buckling of square cupola. We also predict a 'hidden' phase and another magnetoelectric response both of which appear in nonzero magnetic field.PACS numbers: 77.80. Fm,75.85.+t,75.30.Kz Spatial asymmetry is a source of interesting phenomena in a broad range of condensed matter physics. A well-known example is the molecular asymmetry of water H 2 O, which leads to an electric polarization in each molecule. The asymmetry is at play also in magnets: the loss of inversion symmetry activates the asymmetric interactions through the relativistic spin-orbit coupling, such as the Dzyaloshinskii-Moriya (DM) interaction [1,2]. The asymmetric interactions lead to intriguing magnetism, e.g., weak ferromagnetism in antiferromagnets and spin-spiral ordering in helimagnets. They have also attracted growing interest as an origin of the magnetoelectric (ME) effect, that is, cross correlations between dielectricity and magnetism [3,4].Recently, an interesting series of chiral antiferromagnets, A(TiO)Cu 4 (PO 4 ) 4 (A = Ba, Sr) with space group P 42 1 2, was newly synthesized [5]. The materials have a quasi-two-dimensional structure, composed of an alternating array of Cu 4 O 12 clusters, as shown in Fig. 1(a). Each Cu 4 O 12 cluster consists of four corner-sharing CuO 4 plaquettes, forming a noncoplanar buckled structure termed (irregular) square cupola. The asymmetric unit can carry ME-active magnetic multipoles [6] associated with Cu spins. Indeed, a divergent anomaly of the dielectric constant was observed at the Néel temperature (T N =9.5 K) in magnetic fields applied along the [100] and [110] directions for A = Ba [7]. Although the ME response was argued by the magnetic quadrupole associated with noncoplanar antiferromagnetic ordering, the microscopic understanding is not fully obtained. It is highly desired to clarify how the unique asymmetry arising from the square cupolas affects the magnetic and dielectric properties in this series of compounds. [010][001] In this Letter, combining experimental and theoretical studies, we clarify the microscopic mechanism of ME behavior in A(TiO)Cu 4 (PO 4 ) 4 . First, from the magnetization measurement for the compound with A = Ba up to above the saturation field, we find several anomalies depending on the field dire...

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“…Rotating the sample around c and a gives eight different rotation patterns for eight phosphorus ions in the unit cell. Each rotation pattern can be described by the equation: (9) where the constant term K is the Larmor frequency plus average chemical shift; the second term describes the angle dependence of the local field projection to the external field direction. The third term describes the angle dependence of the resonance frequency due to turning of the chemical shift tensor.…”

Section: F Local Magnetic Structure In the Ordered Statementioning

confidence: 99%

Magnetic structure of the square cupola compound Ba(TiO) Cu4(PO4)4

Rästa¹,

Heinmaa²,

Kimura³

et al. 2020

Phys. Rev. B

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The magnetic structure of the antiferromagnetic square cupola compound Ba(TiO)Cu4(PO4)4 with the tetragonal structure is studied with 31 P nuclear magnetic resonance techniques. The magnetic hyperfine shift K shows a clear splitting at the Néel temperature TN = 9.5 K, where the resonance splits into two lines when an external magnetic field is oriented along the c axis and into four lines when the field is along the a axis. In the paramagnetic region K(T ) follows temperature dependence of the magnetic susceptibility χ(T ). From K vs χ plot we determined nearly isotropic hyperfine field values H a hf = 765 mT/µB and H c hf = 740 mT/µB for the magnetic field oriented along a and c, respectively. From the rotation of the single crystal in the external magnetic field we determined eight different orientations of K-tensor in the paramagnetic region. In the antiferromagnetic state at T = 6 K we found that the local field at phosphorus is mainly due to dipolar field of coppers. Here the rotation of the single crystal shows eight different orientations of the local field Bint = 35.6 mT. The orientations correspond to the calculation of dipolar fields at phosphorus assuming magnetic quadrupolar configuration of magnetic moments Γ3(1) described previously [Nat. Commun. 7, 13039 (2016); Phys. Rev. B 96, 214436 (2017)].

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A²⁺ Cation Control of Chiral Domain Formation in A(TiO)Cu₄(PO₄)₄ (A = Ba, Sr)

Cited by 28 publications

References 23 publications

Frustration of square cupola in Sr(TiO) Cu4(PO4)4

Frustration of square cupola in Sr(TiO) Cu4(PO4)4

Magnetoelectric Behavior from S=1/2 Asymmetric Square Cupolas

Magnetic structure of the square cupola compound Ba(TiO) Cu4(PO4)4

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