Helical Magnetic Structure in CsCuCl<sub>3</sub>

Adachi, Ken; Achiwa, N.; Mekata, Mamoru

doi:10.1143/jpsj.49.545

Cited by 135 publications

(92 citation statements)

References 21 publications

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“…The absence of the M s /3 plateau phase for H c should be ascribed to the weak planar anisotropy in Ba 3 CoSb 2 O 9 . It has been reported that hexagonal CsCuCl 3 , which is described as a ferromagnetically stacked triangularlattice antiferromagnet with a small planar anisotropy due to the Dzyaloshinsky-Moriya interaction and the anisotropic exchange interaction [23], shows similar magnetization behaviors, namely, an ill-defined M s /3 plateau-like anomaly for H ab and a small jump for H c at around H s /3 [24]. the magnetic anisotropy in Ba 3 CoSb 2 O 9 should be of the easy-plane type, which will also be confirmed by the analysis of the collective ESR modes, as shown below.…”

mentioning

confidence: 99%

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
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264
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We have performed high-field magnetization and ESR measurements on Ba3CoSb2O9 single crystals, which approximates the two-dimensional (2D) S = 1/2 triangular-lattice Heisenberg antiferromagnet. For an applied magnetic field H parallel to the ab-plane, the entire magnetization curve including the plateau at one-third of the saturation magnetization (Ms) is in excellent agreement with the results of theoretical calculations except a small step anomaly near (3/5)Ms, indicative of a theoretically undiscovered quantum phase transition. However, for H c, the magnetization curve exhibits a cusp near Ms/3 owing to the weak easy-plane anisotropy and the 2D quantum fluctuation. From a detailed analysis of the collective ESR modes observed in the ordered state, combined with the magnetization process, we have determined all the magnetic parameters including the interlayer and anisotropic exchange interactions.PACS numbers: 75.10. Jm, 75.45.+j, 75.60.Ej, Over the past decades, there has been considerable interest in frustrated quantum magnets, owing to a rich variety of exotic quantum phenomena [1][2][3]. For classical spins with an antiferromagnetic coupling, a geometric frustration suppresses the long-range ordering, leading to a degenerate ground state. The degeneracy can be destroyed by quantum fluctuations, which emerge not only through an interplay of strong geometric frustration, low dimensionality, and small spin, but also through the application of a magnetic field. Despite intensive research efforts, the detailed mechanism of the quantum effects, e.g., the ground state property [4,5], has still been highly controversial.One macroscopic manifestation of the quantum phenomena is the stabilization of the "up-up-down" spin structure under a magnetic field, predicted for a twodimensional (2D) triangular-lattice Heisenberg antiferromagnet (TLHAF) with a small spin [6,7]. In a magnetization process, the nonclassical anomaly appears as a plateau in a finite field range at one-third of the saturation magnetization M s , hereafter referred to as the M s /3 plateau. In a classical picture, a monotonic increase in the magnetization is expected up to M s . A number of theoretical approaches for explaining the quantum mechanism of the M s /3 plateau have been proposed [8][9][10][11][12][13][14]. Thus far, however, few numbers of definite experimental results reserved judgment on the issue. This is mainly due to the experimental difficulty in growing the model material, let alone in observing the M s /3 plateau purely driven by quantum fluctuations. In fact, most of the TLHAFs ever studied, such as Cs 2 CuBr 4 , [15,16] have a distorted triangular lattice, which induces an antisymmetric Dzyaloshinsky-Moriya (DM) interaction.It is believed that the spin state in the lower-field range above the higher edge field of the M s /3 plateau is the 2 : 1 canted coplanar state that is a continuous variant of the up-up-down state [7][8][9][10][11]. However, whether the 2 : 1 canted coplanar state is stable up to the saturation or a new quan...

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Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
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264
1
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“…The ferromagnetic (FM) interaction tends to align spin moments, whereas the DM interaction favors perpendicular arrangements of adjacent spins. The resultant spin configuration for CsCuCl 3 is helical arising from the competition of these interactions with a period of 11.8c [5]. …”

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confidence: 99%

“…To date, three incommensurate phases and a commensurate phase have been determined below the spin saturation fields through neutron scattering and thermodynamic measurements [15]. The magnetic structure is expressed by an incommensurate magnetic propagation vector (1/3, 1/3, δ), where δ is 0.085 at zero field [5]. The H-dependence of δ has been well studied [13][14][15][16].…”

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confidence: 99%

Magnetic field induced polar phase in the chiral magnetCsCuCl3

Miyake¹,

Shibuya²,

Akaki³

et al. 2015

Phys. Rev. B

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Magnetoelectric effects in the chiral magnet CsCuCl3 have been investigated through the magnetization and electric polarization measurements in pulsed high magnetic fields. If the magnetic field is applied normal to the spin chiral c-axis, a plateau and a jump in magnetization are observed. Between the plateau and the jump in magnetization, a small but significant electric polarization of about 0.25 µC/m 2 along the a-axis is observed with the field applied almost perpendicular to the ac-plane. In addition, the paramagnetoelectric effect expected from the point group symmetry is confirmed. The emergence of the electric polarization is explained by the cooperation of the local electric polarization on the chiral solitonic spin arrangement and the paramagnetoelectric effect. Hence, we interpret this novel multiferroic phase in CsCuCl3 as a polar solitonic phase.PACS numbers: 75.30.Kz, 75.85.+t Various triangular lattice antiferromagnets (TAFM) have long been studied with the focus on their geometric frustration from the antiferromagnetic coupling of the neighboring spins on a triangular lattice [1][2][3]. Among the TAFM systems, a hexagonal CsCuCl 3 has received sustained interest because of its distinctive chiral crystal structure and its resultant magnetism under applied magnetic fields. The S = 1/2 spins of the Cu 2+ ions form ferromagnetically coupled chains along the c-axis with J 0 = 28 K [4]. The chains are antiferromagnetically coupled and form a triangular lattice in the ab-plane, leading to a 120• spin structure below T N = 10.7 K at zero field [5]: the coupling strength is estimated to J 1 = -4.9 K [7]. The Curie-Weiss temperature obtained by the high-temperature magnetic susceptibility is comparable to T N for the magnetic fields along and perpendicular to the triangular lattice [1,6]. One of the most striking characteristics in CsCuCl 3 is that the Cu-chains are displaced helically in the triangular plane because of the cooperative Jahn-Teller distortion below 423 K [8]: the Cu-chains form helices along the c-axis with a six-ion periodicity [see Fig. 4(b)] [9]. Depending on the chirality, CsCuCl 3 has space group of P 6 1 22 or P 6 5 22 (i.e., point group 622) [10]. The absence of inversion symmetry makes the Dzyaloshinskii-Moriya (DM) interaction active: the strength is estimated to D = 5 K [5], which is comparable with J 1 . The ferromagnetic (FM) interaction tends to align spin moments, whereas the DM interaction favors perpendicular arrangements of adjacent spins. The resultant spin configuration for CsCuCl 3 is helical arising from the competition of these interactions with a period of 11.8c [5].

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“…The period is evaluated as 6/δ = 71.4 Cu-sites, which is almost the same as that in CsCuCl 3 , i.e., 70.6 Cu-sites . 10) It is remarkable that in the present system, the magnetic Bragg peak is observed at Q = (1/3, 1/3, 0), which is absent in CsCuCl 3 . On the other hand, around (1/3, 1/3, 6), the central peak is very weak as compared with the side peaks (see Fig.…”

Section: §1 Introductionmentioning

confidence: 51%

“…The magnetic phase transition occurs at T N = 10.5 K . 10,11) In the ordered state, spins lie in the basal plane and form the 120 • -structure, while along the c-direction, a long period (about 71 triangular layers) helical incommensurate arrangement is realized, due to the competition between the ferromagnetic interaction and the D-M interaction along the chain.…”

Section: §1 Introductionmentioning

confidence: 99%

Oblique triangular antiferromagnetic phase inCsCu1−xCoxCl

et al. 2001

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The spin-1 2 stacked triangular antiferromagnet CsCu1−xCoxCl3 with 0.015 < x < 0.032 undergoes two phase transitions at zero field. The low-temperature phase is produced by the small amount of Co 2+ doping. In order to investigate the magnetic structures of the two ordered phases, the neutron elastic scattering experiments have been carried out for the sample with x ≈ 0.03. It is found that the intermediate phase is identical to the ordered phase of CsCuCl3, and that the low-temperature phase is an oblique triangular antiferromagnetic phase in which the spins form a triangular structure in a plane tilted from the basal plane. The tilting angle which is 42 • at T = 1.6 K decreases with increasing temperature, and becomes zero at TN2 = 7.2 K. An off-diagonal exchange term is proposed as the origin of the oblique phase. §1. Introduction Among the group of antiferromagnets which have a hexagonal ABX 3 triangular structure, many experimental and theoretical investigations for CsCuCl 3 have been done by several authors , 1-4) due to the remarkable features of this compound. Since the Cu 2+ ion is JahnTeller active, CsCuCl 3 undergoes a structural phase transition at T t = 423 K, where Jahn-Teller distorted octahedra CuCl 6 order so that their longest axes form a helix along the c-axis with a repeatlength of six . 5-7) The low-symmetric crystal structure produces the antisymmetric interaction of the Dzyaloshinsky-Moriya (D-M) type between the adjacent spins in the chain with the Dvector parallel to the c-direction. The exchange interactions along and between the chains are ferromagnetic and antiferromagnetic, respectively, and their values have been evaluated as J 0 /k B = 28 K and J 1 /k B = −4.9 K 8, 9) in the definition of H = − 2J ij S i · S j . The magnetic phase transition occurs at T N = 10.5 K . 10, 11) In the ordered state, spins lie in the basal plane and form the 120 • -structure, while along the c-direction, a long period (about 71 triangular layers) helical incommensurate arrangement is realized, due to the competition between the ferromagnetic interaction and the D-M interaction along the chain.Since the magnitude of spin on Cu 2+ is S = 1 2 , quantum fluctuations are important when one describes the magnetic behavior in the magnetic field . 12) Particularly, the magnetization process with a strong field often reveals quantum effects as macroscopic phenomena. Using quantum Monte Carlo calculations or spin wave theory, for the 2D triangular antiferromagnet (TAF) in the isotropic limit, it is predicted that the magnetization plateau appears at around one third of the saturation value M s . 13, 14) According to these predictions, when * Present address: Faculty of Education, Chiba University, 263-8522 Chiba, Japan.the external field H is applied parallel to the c-axis, 2D TAF undergoes a successive phase transition as shown in Fig. 1 (b) low-field coplanar, (c) collinear and (d) highfield coplanar structure in that order. In the field region where the magnetization plateau appears, the spin structure c...

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Helical Magnetic Structure in CsCuCl₃

Cited by 135 publications

References 21 publications

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
27
264
1
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Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
27
264
1
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Magnetic field induced polar phase in the chiral magnetCsCuCl3

Oblique triangular antiferromagnetic phase inCsCu1−xCoxCl

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Helical Magnetic Structure in CsCuCl3

Cited by 135 publications

References 21 publications

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2Susuki1, Kurita2, Tanaka3 et al. 2013Phys. Rev. Lett.217272641View full textAdd to dashboardCite

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2Susuki1, Kurita2, Tanaka3 et al. 2013Phys. Rev. Lett.217272641View full textAdd to dashboardCite

Magnetic field induced polar phase in the chiral magnetCsCuCl3

Oblique triangular antiferromagnetic phase inCsCu1−xCoxCl

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Helical Magnetic Structure in CsCuCl₃

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
27
264
1
View full text Add to dashboard Cite

Magnetization Process and Collective Excitations in theS=1/2Triangular-Lattice Heisenberg AntiferromagnetBa3CoSb2
Susuki
¹
,
Kurita
²
,
Tanaka
³

et al. 2013
Phys. Rev. Lett.
217
27
264
1
View full text Add to dashboard Cite