Relation between ferroelectric and antiferromagnetic order in

Noda, Yukio; Kimura, Hiroyuki; Kamada, Youichi; Osawa, Toshihiro; Fukuda, Y.; Ishikawa, Yoshihisa; Kobayashi, Satoru; Wakabayashi, Yusuke; Sawa, Hiroshi; Ikeda, Naoshi; Kohn, Kay

doi:10.1016/j.physb.2006.05.179

Cited by 34 publications

(41 citation statements)

References 9 publications

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“…The peak positions at the Mn L 2,3 -and O K edges coincide for all temperatures and are in good agreement with the reported positions by neutron scattering [14][15][16]18]. Thanks to the high resolution and the high count rate of the peak, there was no problem in distinguishing the coexisting C-and LTIC-peaks around T 3 (Fig.…”

Section: Temperature Dependencesupporting

confidence: 88%

“…As a function of temperature, YMn 2 O 5 undergoes a sequence of phase transitions, which demonstrate the strong coupling between the magnetic and the FE order: Upon cooling, a transition from paramagnetic to high-temperature incommensurate (HTIC) antiferromagnetic (AFM) occurs at T 1 = 45 K [14]. At T 2 = 39 K the AFM order becomes commensurate (C) with q C = (1/2, 0, 1/4) [14][15][16] and a finite P appears [17]. Upon further cooling, low-temperature incommensurate (LTIC) AFM order sets in at T 3 = 19 K with q LTIC = (0.48, 0, 0.29) [14,18].…”

Section: Introductionmentioning

confidence: 99%

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Resonant soft X-ray scattering studies of multiferroic YMn2O5

Partzsch

Wilkins

Schierle

et al. 2012

Eur. Phys. J. Spec. Top.

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Abstract. We performed soft X-ray resonant scattering at the Mn L 2,3-and OK edges of YMn 2O5. While the resonant intensity at the Mn L2,3 edges reflects the magnetic order parameter, the resonant scattering at the O K edge is found to be directly related to the macroscopic ferroelectric polarization. The latter observation reveals the important role of the spin-dependent Mn-O hybridization for the multiferroicity of YMn 2O5. We present details about how to obtain correct energy dependent lineshapes and discuss the origin of the resonant intensity at the O K edge.

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Section: Temperature Dependencesupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Resonant soft X-ray scattering studies of multiferroic YMn2O5

Partzsch

Wilkins

Schierle

et al. 2012

Eur. Phys. J. Spec. Top.

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“…the cycloidal spin structure of Mn 4+ spins propagating along the c-axis. 6,7,[19][20][21] This structure is also consistent with b-axis polarization.…”

Section: +supporting

confidence: 79%

Role of magnetic chirality in polarization flip upon a commensurate-incommensurate magnetic phase transition in YMn2O5

et al. 2013

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We have performed simultaneous measurements of magnetic chirality by using polarized neutrons and electric polarization along the b-axis of single crystals of YMn 4+ (Mn1−xGax) 3+ O5 with x = 0.047 and 0.12, in which nonmagnetic Ga-ions dilute Mn 3+ spins. The x = 0.047 sample exhibits high-temperature incommensurate (HT-ICM), commensurate (CM), and low-temperature incommensurate (LT-ICM) magnetic phases in order of decreasing temperature, whereas the x = 0.12 sample exhibits only HT-ICM and LT-ICM phases. Here, the CM and LT-ICM phases are ferroelectric and weak-ferroelectric, respectively. Measurements conducted under zero field heating after various field-cooling conditions evidence that the microscopic mechanisms of the spin-driven ferroelectricity in the CM and LT-ICM phases are different: the magnetic chirality of Mn 4+ cycloidal spins plays a dominant role in the LT-ICM phase, whereas the magnetic exchange striction by the Mn 4+ -Mn 3+ chain plays a dominant role in the CM phase. The polarization of YMn2O5 flips upon CM to LT-ICM phase transition because the ferroelectricity driven by the magnetic chirality and the exchange striction provides opposite directions of polarization.Many of the multiferroic compounds that have attracted much attention in recent years exhibit a giant magnetoelectric effect owing to the strong coupling between magnetism and ferroelectricity. The presence of this effect makes these multiferroic compounds potential candidates for industrial device applications. In addition, the coupling mechanism underlying the giant magnetoelectric effect is one of the central issues in this research field.Multiferroic material RMn 2 O 5 (R: rare earth, Bi, and Y)1 provides a unique opportunity for studying the coupling mechanism between magnetism and ferroelectricity. RMn 2 O 5 , which has an orthorhombic structure with the P bam space group, consists of edge-shared Mn 4+ O 6 octahedral chain along the c-axis and pairs of Mn 3+ O 5 pyramids connecting the Mn 4+ O 6 octahedral chains.2 Frustrated spin exchange interactions result in noncollinear magnetic structures and complex magnetic phases.3 RMn 2 O 5 generally exhibits a magnetic phase transition from a paramagnetic to an incommensurate magnetic (HT-ICM) phase at T N 1 , which is typically ∼ 45 K, followed by a successive magnetic phase transition into a commensurate (CM) phase at T CM , typically a few kelvins below T N 1 . Then, at lower temperature, the magnetic structure becomes incommensurate again (a phase referred to as LT-ICM) at T N 2 .4,5 These three magnetic phases exhibit different dielectric properties. The HT-ICM phase is paraelectric, whereas the CM phase exhibits spontaneous polarization concomitantly, and therefore, the CM phase is ferroelectric (FE). The LT-ICM phase is still ferroelectric, however the polarization is suppressed below the CM to LT-ICM phase transition temperature. Thus, the LT-ICM phase is recognized as weak ferroelectric (WFE). Remarkably, a rich variety of magnetoelectric effects have been identified in th...

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confidence: 99%

“…5,10 [16][17][18][19] This spiral-spin order also breaks the inversion symmetry 3,20 and it was considered as an alternative mechanism for ferroelectricity in these compounds. [16][17][18]21 The essential difference between the two proposed mechanisms is the microscopic nature of the exchange coupling that has to be involved. In the spin current ͑spiral͒ model, 22,23 the weak antisymmetric DzyaloshinskiiMoriya interaction ͑ϳS ជ i ϫ S ជ j ͒ creates the magnetoelectric coupling, whereas in the exchange striction model, the FE polarization has its origin in the ionic displacements lifting the frustration of spins interacting via the symmetric exchange ͑or superexchange͒ interactions ͑ϳS ជ i · S ជ j ͒.…”

mentioning

confidence: 99%

Pressure-induced polarization reversal in multiferroicYMn2O5

et al. 2008

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The low-temperature ferroelectric polarization of multiferroic YMn 2 O 5 is completely reversed at a critical pressure of 10 kbar and the phase transition from the incommensurate to the commensurate magnetic phase is induced by pressures above 14 kbar. The high-pressure data correlate with thermal-expansion measurements, indicating a significant lattice strain at the low-temperature transition into the incommensurate phase. The results support the exchange striction model for the ferroelectricity in multiferroic RMn 2 O 5 compounds and they show the importance of magnetic frustration as well as the spin-lattice coupling. DOI: 10.1103/PhysRevB.77.220104 PACS number͑s͒: 77.80.Ϫe, 75.30.Ϫm, 75.50.Ee, 77.84.Bw Multiferroic magnetoelectric compounds in which ferroelectricity and magnetic order coexist and mutually interact have been in the focus of attention very recently because of a wealth of novel physical phenomena observed in these complex materials.1-4 Among the family of multiferroics, the RMn 2 O 5 ͑R ϭ rare earth, Y, Bi͒ manganites are of significant interest because of their extreme complexity with transitions between different commensurate magnetic structures ͑CM͒ and incommensurate ͑IC͒ magnetic structures ͑ICM͒, some of which exhibit ferroelectricity induced by frustrated magnetic orders.5-10 Their common phase sequence upon decreasing temperature T includes transitions from the high-T paramagnetic and paraelectric ͑PE͒ to an antiferromagnetic ͑AFM͒ but still PE phase at T N1 Ӎ 44 K, with an IC magnetic modulation along the orthorhombic a and c axes. At T C1 Ӎ 39 K, a lock-in transition takes place into a CM magnetic phase ͓q ជ = ͑0.5, 0 , 0.25͔͒, which is ferroelectric ͑FE͒. At lower temperature T C2 , all RMn 2 O 5 compounds experience another transition where q ជ unlocks again into different IC values and the FE polarization shows a sharp drop ͑but not necessarily to zero͒. Additional changes of the magnetic order that are identified as spin reorientations in the CM phase have been reported for some RMn 2 O 5 , for example DyMn 2 O 5 ͑Ref. 9͒ and HoMn 2 O 5 .11 It is remarkable that all magnetic ͑and FE͒ phase transitions are clearly resolved in anomalies of the dielectric constant, the FE polarization, and the thermal expansivities, which proves the prominent role of the spin-lattice coupling in the multiferroic properties of these compounds.11,12 The origin of the phase complexity of RMn 2 O 5 lies in the peculiarities of the lattice structure with different magnetic ions ͑Mn 4+ ,Mn 3+ , rare earth͒ and a multitude of partially competing superexchange interactions, leading to a high degree of frustration in the magnetic system. 7 In particular, the smallest loop of nearest-neighbor Mn ions with AFM exchange interactions in the a-b plane has five members, which naturally leads to geometric frustration of the Mn spins.11 Frustrated systems are susceptible to small perturbations such as magnetic fields or pressure, since many different magnetic structures are close in energy and compete for the gro...

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Relation between ferroelectric and antiferromagnetic order in

Cited by 34 publications

References 9 publications

Resonant soft X-ray scattering studies of multiferroic YMn2O5

Resonant soft X-ray scattering studies of multiferroic YMn2O5

Role of magnetic chirality in polarization flip upon a commensurate-incommensurate magnetic phase transition in YMn2O5

Pressure-induced polarization reversal in multiferroicYMn2O5

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