Unfolding of Vortices into Topological Stripes in a Multiferroic Material

Wang, Xueyun; Mostovoy, Maxim; Han, Myung Geun; Horibe, Y.; Aoki, Toshihiro; Zhu, Yimei; Cheong, Sang‐Wook

doi:10.1103/physrevlett.112.247601

Cited by 56 publications

(49 citation statements)

References 24 publications

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“…This two-step nature of the ferroelectric transition in RMnO 3 has been observed experimentally [25]. The lattice responds to external electric field is in agreement with experimental results [15,16,26].…”

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confidence: 87%

A Monte-Carlo Study on the Coupling of Magnetism and Ferroelectricity in the Hexagonal Multiferroic RMnO3

2018

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The ferroelectric phase transition in RMnO 3 breaks both Z 3 and Z 2 symmetries, giving rise to 6 structural domains. Topological protected vortices are formed at the junctions of all 6 domains, and the ferroelectric phase transition is closely related to these Z 6 vortices. In this work, Monte-Carlo studies on both the ferroelectric and magnetic transition have been performed on RMnO 3 system. The magnetic simulation results on lattices with different structural domain distributions induced by external electric field and simulated quenching show different magnetic transition temperature T s , indicating that the coupling of magnetism and ferroelectricity is through the Z 6 structural domain. At extreme case, lattice quenched from above the ferroelectric transition results in high vortex density, which can drive the system into spin glass.Multiferroics are materials that host magnetism and ferroelectricity in a single phase [1]. The potential of having magnetism and ferroelectricity coupling makes these materials of great importance both technologically and scientifically. Judging by the source of magnetism and ferroelectricity, multiferroics can be categorized into type-I and type-II: in type-I multiferroics the magnetism and ferroelectricity have different origins and are often well separated in transition temperatures, whereas in type-II multiferroics the magnetism is the cause of ferroelectricity [2][3][4]. As a typical type-I multiferroic, the hexagonal RMnO 3 (R = Y, Lu, Sc, · · · ) becomes ferroelectric below T C ∼ 570-990 K when the crystal breaks the Z 3 symmetry of the high temperature P6 3 mmc phase through a structural instability of the Mn and O atoms due to trimerization [5][6][7]. The trimerization then leads to the rare earth atom splitting into two atomic sites which breaks the Z 2 symmetry and gives rise to polarization, as illustrated in Figure 1b. The space group of the ferroelectric phase is P6 3 cm [8]. Since the Mn atoms form triangular lattice in the xy-plane, the system becomes geometrically frustrated [9]. Below T N ∼ 90 K, the magnetic moment of Mn orders in a 120 • arrangement [8,10]. The weak interaction between magnetism and ferroelectricity in RMnO 3 was observed through in-plane dielectric anomaly [11].The Z 3 × Z 2 symmetry breaking in the ferroelectric transition of RMnO 3 creates 6 structural domains. As shown in Figure 1a-c, RMnO 3 consists of corner sharing MnO 5 bipyramid layers separated by the rare earth atom layers. From the top view, each MnO 5 bipyramid is surrounded by 3 rare earth atoms (α, β, γ). The trimerization involves tilting of the bipyramids towards one of the 6 symmetry equivalent directions: α + , β + , γ + , α − , β − , γ − , each of which corresponds to a structural domain [6]. This has been confirmed by observations using optics second harmonic generation, SEM, STM and AFM [6,[12][13][14][15][16]. Both the magnetic and ferroelectric order parameters are confined in the xy-plane due to the crystal geometry [17]. Based on this feature, a 2D 6-fold clock mode...

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confidence: 87%

A Monte-Carlo Study on the Coupling of Magnetism and Ferroelectricity in the Hexagonal Multiferroic RMnO3

2018

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“…However, when a h-RMnO 3 crystal with stripe domains is heated above and cooled down across T c , vortex domains form everywhere in the crystal, and the density of vortices decreases with the decreasing cooling rate across T c . [21][22][23] It turns out that the zoo of Z 2 × Z 3 vortices is, in fact, a forest of thermally excited three-dimensional vortex lines spanning the entire crystal, which result from the emergent continuous U(1) symmetry near the critical temperature. 24 It appears that the Kibble-Zurek mechanism, [25][26][27][28] which is initially proposed to explain the early universe formation, is also responsible for the network formation of multiferroic vortices through a continuous phase transition.…”

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confidence: 99%

Self-poling with oxygen off-stoichiometry in ferroelectric hexagonal manganites

Wang

Huang

et al. 2015

APL Materials

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“…The control of vortices, such as the transformation of vortices into stripes, has not been achieved with external electric fields, probably because of the tendency toward charge cancellation at vortex cores 31 . Instead, shear strain with a strain gradient applied at high temperatures has been demonstrated to be an effective tool for vortex control 107 . Shear strain induces a Magnus-type force 110 acting in opposite ways on vortices and antivortices along the direction normal to the shear strain.…”

Section: Unfolding Of Z6 Vortex Coresmentioning

confidence: 99%