Magnetic phases of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CsCuCl</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: Anomalous critical behavior

Weber, Heiko B.; Werner, Tomasz; Wosnitza, J.; Löhneysen, H. v.; Schotte, U.

doi:10.1103/physrevb.54.15924

Cited by 39 publications

(40 citation statements)

References 27 publications

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“…The magnetic phase transition of CsCuCl 3 was recently studied by neutron diffraction by Mekata et al [101], by Stüsser et al [102], and by specific-heat measurements by Weber et al [103]. Mekata et al obtained β = 0.25±0.01 while Stüsser et al obtained [102] β = 0.23 ± 0.02, which were close to the n = 2 chiral value and that of CsMnBr 3 .…”

Section: (B) Helimagnetsmentioning

confidence: 89%

“…Experimental observation reported in Ref. 103 that external fields applied along the c-axis made the deviation from the ideal chiral critical behavior less pronounced can naturally be understood from such crossover picture, because the c-axis field tends to confine the noncollinear spin structure in a plane orthogonal to the field, thus relatively weakening the crossover due to the canting effect of the D-vector.…”

Section: (B) Helimagnetsmentioning

confidence: 99%

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Kawamura¹

1998

J. Phys.: Condens. Matter

340

470

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Recent theoretical and experimental studies on the critical properties of frustrated antiferromagnets with the noncollinear spin order, including stacked-triangular antiferromagnets and helimagnets, are reviewed. Particular emphasis is put on the novel critical and multicritical behaviors exhibited by these magnets, together with an important role played by the 'chirality'. §1. Introduction Phase transitions and critical phenomena have been a central issue of statistical physics for many years. In particular, phase transitions of magnets or of 'spin systems' have attracted special interest. Thanks to extensive theoretical and experimental studies, we now have rather good understanding of the nature of phase transitions of standard ferromagnets and antiferromagnets. By the term 'standard', I mean here regular and unfrustrated magnets without quenched disorder and frustration. They include ferromagnets and unfrustrated antiferromagnets with the collinear spin order.One key notion which emerged through these studies is the notion of universality. According to the universality hypothesis, a variety of continuous (or secondorder) phase transitions can be classified into a small number of universality classes determined by a few basic properties characterizing the system under study, such as the space dimensionality d, the symmetry of the order parameter and the range of interaction. If one is interested only in the so-called universal quantities, such as critical exponents, amplitude ratios and scaled equation of state, various phase transitions should exhibit exactly the same behavior. In the case of standard bulk magnets in three spatial dimensions (d = 3), universality class is basically determined by the number of the spin components, n. Physically, the index n is related to the type of magnetic anisotropy: Namely, n = 1 (Ising), n = 2 (XY ) and n = 3 (Heisenberg) correspond to magnets with easy-axis-type anisotropy, easy-plane-type anisotropy and no anisotropy (isotropic magnets), respectively. The critical properties associated with these n-component O(n) universality classes have been extensively studied and are now rather well understood. From the renormalization-group (RG) viewpoint, these critical properties are governed by the so-called Wilson-Fisher O(n) fixed point.

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Section: (B) Helimagnetsmentioning

confidence: 89%

Section: (B) Helimagnetsmentioning

confidence: 99%

Untitled

Kawamura¹

1998

J. Phys.: Condens. Matter

340

470

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“…Until recently, CsCuCl 3 was believed to undergo a second order phase transition with exponents compatible with those of group 1, see Table I. It has been finally found to display a weak first order phase transition [90].…”

Section: The Experimental Situationmentioning

confidence: 99%

“…The first one is made of ABX 3 hexagonal perovskites -where A is an alkali metal, B a transition metal and X a halogen atom -which are physical realizations of XY STA. The most studied ones are CsMnBr 3 , CsCuCl 3 , CsNiCl 3 and CsMnI 3 (see [89] for a review and [90] for RbMnBr 3 . We have excluded this material since the measurement of its specific heat presents a shoulderlike anomaly near T c which renders the determination of α and β doubtful).…”

Section: The Experimental Situationmentioning

confidence: 99%

Nonperturbative renormalization-group approach to frustrated magnets

2004

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This article is devoted to the study of the critical properties of classical XY and Heisenberg frustrated magnets in three dimensions. We first analyze the experimental and numerical situations. We show that the unusual behaviors encountered in these systems, typically nonuniversal scaling, are hardly compatible with the hypothesis of a second order phase transition. Moreover, the fact that the scaling laws are significantly violated and that the anomalous dimension is negative in many cases provides strong indications that the transitions in frustrated magnets are most probably of very weak first order. We then review the various perturbative and early nonperturbative approaches used to investigate these systems. We argue that none of them provides a completely satisfactory description of the three-dimensional critical behavior. We then recall the principles of the nonperturbative approach -the effective average action method -that we have used to investigate the physics of frustrated magnets. First, we recall the treatment of the unfrustrated -O(N ) -case with this method. This allows to introduce its technical aspects. Then, we show how this method unables to clarify most of the problems encountered in the previous theoretical descriptions of frustrated magnets. Firstly, we get an explanation of the long-standing mismatch between different perturbative approaches which consists in a nonperturbative mechanism of annihilation of fixed points between two and three dimensions. Secondly, we get a coherent picture of the physics of frustrated magnets in qualitative and (semi-) quantitative agreement with the numerical and experimental results. The central feature that emerges from our approach is the existence of scaling behaviors without fixed or pseudo-fixed point and that relies on a slowing-down of the renormalization group flow in a whole region in the coupling constants space. This phenomenon allows to explain the occurence of generic weak first order behaviors and to understand the absence of universality in the critical behavior of frustrated magnets.

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“…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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Magnetic phases ofCsCuCl3: Anomalous critical behavior

Cited by 39 publications

References 27 publications

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Nonperturbative renormalization-group approach to frustrated magnets

Oblique triangular antiferromagnetic phase inCsCu1−xCoxCl

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