Structural and magnetic properties of pseudo-two-dimensional triangular antiferromagnets Ba3MSb2O9(M = Mn, Co, and Ni)

Doi, Yoshihiro; Hinatsu, Yukio; Ohoyama, Kenji

doi:10.1088/0953-8984/16/49/009

Cited by 93 publications

(120 citation statements)

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“…Due to a strong spin-orbit coupling with a uniaxial crystal field, the ground state of Co 2+ ions is reduced to an effective spin-1/2 moment at temperatures below ∼ 250 K. 9,11 In the ab-plane these moments form a triangular lattice which are stacked directly on top of each other (space group P6 3 /mmc). The dominant magnetic coupling is attributed to the nearest-neighbor exchange interaction within the plane (J = 18 K), while the magnetic interlayer interaction (J ⊥ = 0.48 K) is known to be much smaller as the planes are separated by double layers of nonmagnetic Sb ions.…”

Section: 10mentioning

confidence: 99%

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

et al. 2015

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Using high resolution sound velocity measurements we have obtained a very precise magnetic phase diagram of Ba3CoSb2O9 a material that is considered to be an archetype of the spin 1/2 triangular-lattice antiferromagnet. Results obtained for the field parallel to the basal plane (up to 18 T) show three phase transitions, consistent with predictions based on simple 2D isotropic Heisenberg models and previous experimental investigations. The phase diagram obtained for the field perpendicular to the basal plane clearly reveals an easy-plane character of this compound and in particular, our measurements show a single first order phase transition at Hc1 = 12.0 T which can be attributed to a spin-flop between an umbrella-type configuration and a coplanar V-type order where spins lie in a plane perpendicular to the ab-plane. A low temperatures softening of the lattice within some of the ordered phases is also observed and may be a result of residual spin fluctuations.

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Section: 10mentioning

confidence: 99%

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

et al. 2015

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“…Since the magnetic layers are separated by nonmagnetic layers consisting of the Sb 2 O 9 double octahedron and Ba 2+ ions, the intralayer exchange interaction is expected to be dominant. On the other hand, the antiferromagnetic ordering at the Néel temperature T N ≈ 3.8 K [18,20] is due to the weak interlayer exchange interaction. The DM interaction is absent in Ba 3 CoSb 2 O 9 because of the highly symmetric crystal structure with the space group P 6 3 /mmc.…”

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“…Magnetic Co 2+ ions form uniform triangular-lattice layers parallel to the ab-plane [19,20]. Since the magnetic layers are separated by nonmagnetic layers consisting of the Sb 2 O 9 double octahedron and Ba 2+ ions, the intralayer exchange interaction is expected to be dominant.…”

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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
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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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“…16,18,19) In Ba 3 NiSb 2 O 9 , the uniform triangular lattice of magnetic ions is realized as in Ba 3 CoSb 2 O 9 . Indeed, recently it has been found that the magnetization curve of this compound also exhibits a clear 1/3 plateau.…”

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The Magnetization Process of the Spin-One Triangular-Lattice Heisenberg Antiferromagnet

et al. 2013

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Starting with Wannier's 1) and Anderson's 2) seminal papers the triangular-lattice antiferromagnet has attracted a lot of attention. One spectacular feature of this model system for a strongly frustrated magnet is the unconventional magnetization process of the triangular-lattice Heisenberg antiferromagnet. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] While for the classical isotropic Heisenberg model at zero temperature the magnetization M increases linearly with the applied magnetic field H, thermal or quantum fluctuations induce a plateau at 1/3 of the saturation magnetization M sat (''order from disorder'' phenomenon). For the extreme quantum case, i.e., spin quantum number s ¼ 1=2, this plateau at T ¼ 0 has been widely discussed. Very recently an almost perfect experimental realization of an s ¼ 1=2 triangular-lattice Heisenberg antiferromagnet has been reported for Ba 3 CoSb 2 O 9 , 17) where the entire measured magnetization curve MðHÞ including the 1/3 plateau is in excellent agreement with theoretical predictions. In particular, the theoretical magnetization data obtained by high-order coupled-cluster approximation 11) and by large-scale exact diagonalization approach 15) almost coincide with the measured ones over a wide range of the magnetic field.Another interesting triangular-lattice magnet is Ba 3 -NiSb 2 O 9 that is considered as a good candidate of an s ¼ 1 triangular-lattice Heisenberg antiferromagnet. 16,18,19) In Ba 3 NiSb 2 O 9 , the uniform triangular lattice of magnetic ions is realized as in Ba 3 CoSb 2 O 9 . Indeed, recently it has been found that the magnetization curve of this compound also exhibits a clear 1/3 plateau. 16) By contrast to the wellinvestigated spin-half case there are much less reliable theoretical studies of the s ¼ 1 model relevant for Ba 3 NiSb 2 O 9 . Motivated by the excellent agreement of theoretical predictions based on exact diagonalization (ED) and coupled-cluster method (CCM) and experimental results for the spin-half compound Ba 3 CoSb 2 O 9 reported in Ref. 17 we apply in this paper these methods to the s ¼ 1 model to provide theoretical data to compare with experimental results.For the s ¼ 1 model the Lanczos ED for N ¼ 27 sites and the CCM-SUBn-n approximation 20) for n ¼ 2; 4; 6; 8 are used to calculate the field-dependent properties of the model.In this short note we will not explain details of the Lanczos ED and the CCM. We refer the interested reader e.g., to Refs. 15,21, 22 and 11,[23][24][25] respectively. First we report the main theoretical results. The saturation field is H sat ¼ 9Js ¼ 9J, where J is the nearest-neighbor exchange coupling. The zero-field uniform susceptibility calculated with CCM-SUBn-n approximation is ¼ 0:10790, 0.09932, 0.09785, and 0.09679 for n ¼ 2, 4, 6, and 8, respectively. Moreover, it is useful to extrapolate the ''raw'' SUBn-n data to n ! 1 by ðnÞ ¼ c 0 þ c 1 ð1=nÞ þ c 2 ð1=nÞ 2 which yields finally our CCM estimate for the susceptibility CCM ¼ 0:0956. This value is in excellent agreement with the spin-wave res...

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Structural and magnetic properties of pseudo-two-dimensional triangular antiferromagnets Ba₃MSb₂O₉(M = Mn, Co, and Ni)

Cited by 93 publications

References 28 publications

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

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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The Magnetization Process of the Spin-One Triangular-Lattice Heisenberg Antiferromagnet

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Structural and magnetic properties of pseudo-two-dimensional triangular antiferromagnets Ba3MSb2O9(M = Mn, Co, and Ni)

Cited by 93 publications

References 28 publications

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

Magnetic phase diagram ofBa3CoSb2O9as determined by ultrasound velocity measurements

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

The Magnetization Process of the Spin-One Triangular-Lattice Heisenberg Antiferromagnet

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Structural and magnetic properties of pseudo-two-dimensional triangular antiferromagnets Ba₃MSb₂O₉(M = Mn, Co, and Ni)

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