Successive Magnetic Ordering in CuFeO<sub>2</sub>–A New Type of Partially Disordered Phase in a Triangular Lattice Antiferromagnet–

Mekata, Mamoru; Yaguchi, Nariyasu; Takagi, Toshimi; Sugino, T.; Mitsuda, Setsuo; Yoshizawa, H.; Hosoito, Nobuyoshi; Shinjo, Teruya

doi:10.1143/jpsj.62.4474

Cited by 142 publications

(137 citation statements)

References 17 publications

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“…In addition, we carried out a detailed analysis of the temperature dependences of hyperfine parameters, and a discussion is provided in light of the peculiarities of the electronic and magnetic states of the iron ions in 3R-AgFeO 2 . The obtained data are compared with earlier published Mössbauer data for the CuFeO 2 [27][28][29][30][31][32] and BiFeO 3 [35,36] also revealing multiferroic properties. (heating time to the desired temperatures was 10 min) in a belt-type high-pressure apparatus.…”

mentioning

confidence: 73%

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Sobolev¹,

Rusakov²,

Moskvin³

et al. 2017

J. Phys.: Condens. Matter

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We report new results of a 57 Fe Mössbauer study of multiferroic 3R-AgFeO 2 powder samples performed in a wide temperature range, including two points, T N1 » 14 K and T N2 » 9 K, of magnetic phase transitions. At the intermediate temperature range, T N2 < T < T N1 , the 57 Fe Mössbauer spectra can be described in terms of collinear spin-density-waves (SDW) with the inclusion of many high-order harmonics, indicating that the real magnetic structure of this ferrite appears to be more complicated than a pure sinusoidally modulated SDW. The spectra at low temperatures, T < T N2 , consist of a Zeeman pattern with line broadenings and sizeable spectral asymmetry. It has been shown that the observed spectral shape is consistent with a transition to the elliptical cycloidal magnetic structure. An analysis of the experimental spectra was carried out under the assumption that the electric hyperfine interactions are modulated when the Fe 3+ magnetic moment rotates with respect to the principal axis of the EFG tensor and emergence of the strong anisotropy of the magnetic hyperfine field H hf at the 57 Fe nuclei. The large and temperatureindependent anharmonicity parameter, m » 0.78, of the cycloidal spin structure obtained from the experimental spectra results from easy-axis anisotropy in the plane of rotation of the iron spin.Analysis of different mechanisms of spin and hyperfine interactions in 3R-AgFeO 2 and its structural analogue CuFeO 2 points to a specific role played by the topology of the exchange coupling and the oxygen polarization in the delafossite structures.

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mentioning

confidence: 73%

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Sobolev¹,

Rusakov²,

Moskvin³

et al. 2017

J. Phys.: Condens. Matter

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“…The frustration may be more effective for inner Cu spins than outer Cu spins as expected in Cu 3 Mo 2 O 9 . In addition to Cu 3 (OH) 4 AO 4 (A = S or Se), a part of spins are perfectly or nearly disordered in the ordered state in several frustrated Heisenberg antiferromagnets such as the spinel antiferromagnet GeNi 2 O 4 [52], the pyrochlore antiferromagnet Gd 2 Ti 2 O 7 , [53] and the triangular lattice antiferromagnets CuFeO 2 [54] and Ag 2 CrO 2 [55]. Exchange interactions in long M − M bonds, where M represents a magnetic ion, play an important role in the occurrence of the PD states.…”

Section: Discussionmentioning

confidence: 99%

Magnetic structure of thespin−12frustrated quasi-one-dimensional antiferromagnetCu3Mo2O9
Hase
¹
,
Kuroe
²
,
Pomjakushin
³

et al. 2015
Phys. Rev. B
17
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13
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We investigated the crystal and magnetic structures of the spin-1/2 frustrated antiferromagnet Cu3Mo2O9 in which the spin system consists of antiferromagnetic chains and dimers. The space group at room temperature has been reported to be orthorhombic P nma (No. 62). We infer that the space group above TN = 7.9 K is monoclinic P 21/m (No. 11) from the observation of reflections forbidden in P nma in x-ray powder diffraction experiments at room temperature. We determined the magnetic structure of Cu3Mo2O9 in neutron powder diffraction experiments. Magnetic moments on dimer sites lie in the ac planes. The magnitudes are 0.50 ∼ 0.74µB. Moments on chain sites may exist but the magnitudes are very small. The magnetic structure indicates that a partial disordered state is realized. We consider the origin of the magnetic structure, weak ferromagnetism, and electric polarization.

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“…In some cases, a number of superposed symmetryrelated k modes within the first Brillouin zone form a socalled multiple-k order [6,7,13,14]. A particular interesting form of such modulated magnetism is a partially ordered state (POS) with periodically arranged "paramagnetic" sites [15][16][17][18]. These fluctuating magnetic moments decimate a fraction of the energy-costly frustrated bonds while retaining an extensive entropy, hence lowering the free energy.…”

Section: A) B)mentioning

confidence: 99%

Fluctuation-Driven Selection at Criticality in a Frustrated Magnetic System: The Case of Multiple-kPartial Order on the Pyrochlore Lattice

et al. 2015

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We study the problem of partially ordered phases with periodically arranged disordered (paramagnetic) sites on the pyrochlore lattice, a network of corner-sharing tetrahedra. The periodicity of these phases is characterized by one or more wave vectors k = { 1 2 1 2 1 2 }. Starting from a general microscopic Hamiltonian including anisotropic nearest-neighbor exchange, long-range dipolar interactions and second-and third-nearest neighbor exchange, we identify using standard mean-field theory (s-MFT) an extended range of interaction parameters that support partially ordered phases. We demonstrate that thermal fluctuations ignored in s-MFT are responsible for the selection of one particular partially ordered phase, e.g. the "4-k" phase over the "1-k" phase. We suggest that the transition into the 4-k phase is continuous with its critical properties controlled by the cubic fixed point of a Ginzburg-Landau theory with a 4-component vector order-parameter. By combining an extension of the Thouless-Anderson-Palmer method originally used to study fluctuations in spin glasses with parallel-tempering Monte-Carlo simulations, we establish the phase diagram for different types of partially ordered phases. Our results elucidate the long-standing puzzle concerning the origin of the 4-k partially ordered phase observed in the Gd2Ti2O7 dipolar pyrochlore antiferromagnet below its paramagnetic phase transition temperature. Highly frustrated magnetism is one of the paradigms of modern condensed matter physics [1]. In frustrated magnets, the combination of lattice geometry and competing interactions often leads to degenerate classical states. The degeneracies are generally accidental as they are not protected by the symmetries of the spin Hamiltonian. Yet, the degenerate states may be related by transformations that form an emergent symmetry group. Near a continuous phase transition, these approximate symmetries provide "organizing principles" in determining the critical properties by distinguishing relevant perturbations from irrelevant ones. In the most interesting case, the leading degeneracy-lifting perturbations, which may be relevant or irrelevant in the renormalization group sense, are thermal or quantum fluctuations -a phenomenon called order-by-disorder (ObD) [2][3][4][5]. The competition among diverse degeneracy-lifting effects can result in a modulated long-range ordered state at nonzero wave vector k, which may or may not be commensurate with the lattice [6][7][8][9][10][11][12]. In some cases, a number of superposed symmetryrelated k modes within the first Brillouin zone form a socalled multiple-k order [6,7,13,14]. A particular interesting form of such modulated magnetism is a partially ordered state (POS) with periodically arranged "paramagnetic" sites [15][16][17][18]. These fluctuating magnetic moments decimate a fraction of the energy-costly frustrated bonds while retaining an extensive entropy, hence lowering the free energy.In this Letter, we study the convergence of the aforementioned phenomena (emergent symmet...

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Successive Magnetic Ordering in CuFeO₂–A New Type of Partially Disordered Phase in a Triangular Lattice Antiferromagnet–

Cited by 142 publications

References 17 publications

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Magnetic structure of thespin−12frustrated quasi-one-dimensional antiferromagnetCu3Mo2O9
Hase
¹
,
Kuroe
²
,
Pomjakushin
³

et al. 2015
Phys. Rev. B
17
1
13
0
View full text Add to dashboard Cite

Fluctuation-Driven Selection at Criticality in a Frustrated Magnetic System: The Case of Multiple-kPartial Order on the Pyrochlore Lattice

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Successive Magnetic Ordering in CuFeO2–A New Type of Partially Disordered Phase in a Triangular Lattice Antiferromagnet–

Cited by 142 publications

References 17 publications

57Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO2

57Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO2

Magnetic structure of thespin−12frustrated quasi-one-dimensional antiferromagnetCu3Mo2O9Hase1, Kuroe2, Pomjakushin3 et al. 2015Phys. Rev. B171130View full textAdd to dashboardCite

Fluctuation-Driven Selection at Criticality in a Frustrated Magnetic System: The Case of Multiple-kPartial Order on the Pyrochlore Lattice

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Successive Magnetic Ordering in CuFeO₂–A New Type of Partially Disordered Phase in a Triangular Lattice Antiferromagnet–

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Magnetic structure of thespin−12frustrated quasi-one-dimensional antiferromagnetCu3Mo2O9
Hase
¹
,
Kuroe
²
,
Pomjakushin
³

et al. 2015
Phys. Rev. B
17
1
13
0
View full text Add to dashboard Cite