Predicted energetics and properties of rare-earth ferrites films grown on cubic (1 1 1)- and hexagonal (0 0 0 1)-oriented substrates

Zhao, Hong Jian; Xu, Changsong; Yang, Yurong; Duan, Wenhui; Chen, Xiang Ming; Bellaïche, L.

doi:10.1088/0953-8984/27/48/485901

Cited by 7 publications

(16 citation statements)

References 35 publications

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“…As further indicated in the phase diagram of Figure a, the YMnO 3 ‐type phase, which is of P6 3 cm symmetry and thus hexagonal and polar, becomes the ground state of our investigated epitaxial BFO films, for a IP ranging between 6.13 and 6.21 Å. Such range of lattice constants strongly suggests that it is possible to experimentally observe for the first time hexagonal BFO films by growing them on a rhombohedral Cr 2 O 3 (0001) substrate, since this latter system has an effective lattice constant of 6.19 Å . The observation of the P6 3 cm phase of BFO should be feasible even if the corresponding strain (with respect to BFO bulk) is larger than 10% because this phase is a polymorph form of BFO, in the same manner than the so‐called T‐like state was experimentally seen in (001) BFO films for compressive strains being larger than 7% in magnitude .…”

Section: Resultssupporting

confidence: 52%

“…Figure a shows that this polarization changes from 6.24 µC cm −2 for a IP = 6.0 Å to 9.82 µC cm −2 for a IP = 6.40 Å, that is it increases by about 57.4%. Such enhancement is rather surprising and original when realizing that the (out‐of‐plane) polarization of hexagonal rare‐earth manganites and ferrites have been reported to decrease, rather than increase, with tensile strain. To shed more light into such unusual evolution of the polarization in the P6 3 cm phase of BFO, Figure b reports the behavior of different phonon modes of this state as a function of a IP .…”

Section: Resultsmentioning

confidence: 99%

“…Three of them (namely, R3c , Cc‐I , and Cc‐II ) crystallize in the perovskite structure and are grown along their pseudocubic [111] direction, which can be practically accomplished by using cubic (111) or hexagonal (0001) substrates—as schematized in Figure d and described in ref. . The out‐of‐plane direction of the remaining three states (that are P6 3 cm , P

\overset{3}{true}

c1 , and a phase we coined here as “hex‐like” P1 ) is basically along the hexagonal [0001] axis, which can also be made possible by growing them on cubic (111) substrates (such as yttrium stabilized zirconium oxide (YSZ)), or hexagonal (0001) substrates (e.g., Cr 2 O 3 and Fe 2 O 3 ) .…”

Section: Resultsmentioning

confidence: 99%

“…. The out‐of‐plane direction of the remaining three states (that are P6 3 cm , P

\overset{3}{true}

Section: Resultsmentioning

confidence: 99%

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Novel Multiferroic Phases and Phenomena in Epitaxial (111) BiFeO₃ Films

Xiang

Bellaïche

2017

Adv Elect Materials

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For example, bismuth ferrite (BiFeO 3 or BFO) perovskite, which is likely the most studied multiferroic system to date because of its large polarization and high ordering temperatures, [9,10] has a relatively weak magnetoelectric coupling in its bulk form [11] (which adopts the so-called R-phase [12] ), which hinders its technical application. Similarly, the other intensively studied class of multiferroics formed by hexagonal ReMnO 3 and ReFeO 3 materials, where Re is a rare-earth or the Y ion (see, e.g., refs. [13] and [14] and references therein), has a relatively small value for their out-of-plane polarization (e.g., ≈6 µC cm −2 in YMnO 3 [15,16] ) due to their improper character, which may be a disadvantage to their utilization in devices.As a result, searching for novel multiferroic materials or even novel phases in already known multiferroics constitutes an active research activity. [12,[17][18][19][20][21][22][23] For instance, the discovery of a novel multi ferroic phase, the so-called T-phase, in BFO systems grown as thin films along the pseudocubic [001] direction and under large compressive strain [12,24] has generated a large interest, especially since large magnetoelectric effects have been predicted to occur near the strain-induced boundary between the R and T phases. [25,26] Based on the aforementioned findings and the fact that paraelectric magnetic perovskites made of ReFeO 3 have been recently predicted to transform into polar hexagonal YMnO 3 -type phases (and thus to become multiferroic) when grown on top of (111) cubic or (0001) hexagonal substrates exercising a large enough tensile strain, [27] it is legitimate to wonder if such latter, rather atypical for now, conditions of growth and epitaxial strain can also give rise to novel multiferroic phases and effects in BFO films.The goal of this paper is to reveal that epitaxial (111) BiFeO 3 films are indeed predicted to adopt new multiferroic phases when placed under large enough tensile strain. For instance, they can exhibit not only the polar hexagonal YMnO 3 -type configuration but also another brand new crystal structure of triclinic symmetry. These hexagonal and triclinic states are further numerically found to display unusual properties, such as an out-of-plane polarization anomalously increasing when increasing tensile epitaxial strain (due to the appearance of a proper ferroelectric character) and an electrically controllable spiral magnetism, respectively. In particular, the presently determined triclinic structure appears to be rather promising to induce strong or novel magnetoelectric effects, due to the fact Multiferroics are attracting much interest because they simultaneously possess ordered electric and magnetic dipoles. In particular, numerous recent studies are devoted to find novel multiferroic phases, as, for example evidenced by the flurry of activities that accompanied the discovery of the so-called T-phase in BiFeO 3 systems, when these latter are made in forms of (001) epitaxial films and subject to high-enough compressi...

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

\overset{3}{true}

Section: Resultsmentioning

confidence: 99%

“…. The out‐of‐plane direction of the remaining three states (that are P6 3 cm , P

\overset{3}{true}

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Novel Multiferroic Phases and Phenomena in Epitaxial (111) BiFeO₃ Films

Xiang

Bellaïche

2017

Adv Elect Materials

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“…a) Computed Kohn–Sham energy plotted as a function of the formula‐cell volume of LFO for both hexagonal ( P 6 3 cm ) and orthorhombic ( Pbnm ) phases. Unlike similar previous calculations, we did not examine detailed epitaxial strain effects since this simplified treatment does not alter our prediction of the morphotropic phase coexistence to a significant degree. b) 2 θ–θ x‐ray diffraction (XRD) patterns of the 300‐nm‐thin LFO film grown on a Pt/Al 2 O 3 (0001) substrate under several different deposition conditions.…”

mentioning

confidence: 99%