Jahn-Teller distortion induced charge ordering in the CE phase of manganites

Dong, Shuai; Dai, Shaotao; Yao, Xincheng; Wang, K. F.; Zhu, Chong; Liu, Jun‐Min

doi:10.1103/physrevb.73.104404

Cited by 19 publications

(4 citation statements)

References 25 publications

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“…The theoretical treatment based only on electronic mechanism of orbital ordering 12,13 gives a rather good description of half-doped manganites, which reproduces the original assignment of occupied 3x 2 − r 2 /3y 2 − r 2 orbitals. However, to get a better insight into an actual physical situation, one should also include explicitly electron-lattice interaction as well as crystal-field effects.…”

Section: Introductionmentioning

confidence: 77%

Relationship between orbital structure and lattice distortions in Jahn-Teller systems

et al. 2011

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Analyzing the orbital structure and lattice distortions in the CE phase of half-doped manganites, we demonstrate that the usual approach directly relating the orbital occupation of Jahn-Teller ions to the displacements of neighboring ligands may be misleading. For the correct identification of orbital structure, it is necessary to take self-consistently into account the electron-lattice interactions, kinetic energy of charge carriers, and crystal-field effects. In certain situations, e.g. in the CE phase of single-layered manganite La0.5Sr1.5MnO4, the type of orbital ordering strongly deviates from that, which one would deduce from the local lattice distortions.

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Section: Introductionmentioning

confidence: 77%

Relationship between orbital structure and lattice distortions in Jahn-Teller systems

et al. 2011

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“…Here the CO phase is specified as the CE-type CO phase, which is the common ground state in the half-doped (T 1/2 D 1/2 MnO 3 ) narrow bandwidth manganites. 15 In the CE ground state, Mn cations form FM zigzag chains in X-Y plane, with antiferromagnetic (AFM) couplings between the neighboring chains in X-Y plane and neighboring sites along Z axis. 16 For this spin structure, each Mn has four AFM and two FM coupling bonds with its nearest neighbors (NN).…”

Section: 6mentioning

confidence: 99%

Surface phase separation in nanosized charge-ordered manganites

Dong

Gao

Wang

et al. 2007

Applied Physics Letters

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117

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Recent experiments showed that the robust charge-ordering in manganites can be weakened by reducing the grain size down to nanoscale. Weak ferromagnetism was evidenced in both nanoparticles and nanowires of charge-ordered manganites. To explain these observations, a phenomenological model based on surface phase separation is proposed. The relaxation of superexchange interaction on the surface layer allows formation of a ferromagnetic shell, whose thickness increases with decreasing grain size. Possible exchange bias and softening of the ferromagnetic transition in nanosized charge-ordered manganites are predicted.PACS numbers: 75.50. Tt, 75.47.Lx, 61.30.Hn Perovskite manganites are typical strongly correlated electron systems with a general formula T 1−x D x MnO 3 , where T is a trivalent rare earth element and D is a divalent alkaline earth element. Fascinating properties of manganites, e.g. phase separation (PS), charge-ordering, insulator-metal transition (IMT), etc, were revealed in the last decade.1 Due to the competitive interactions engaged in manganites, various electronic phases of very different magnetotransport behaviors are quite close in free energy, allowing us opportunities to regulate these properties by external perturbations. For instance, both colossal magnetoresistance (CMR) 2 and colossal electroresistance (CER) 3 in manganites are the results of IMT. In general, the sequence of CMR or CER in chargeordered (CO) manganites can be regarded as a melting of the CO phase into ferromagnetic (FM) metal under magnetic or electrical field. However, the required field for such a sequence is too high for practical applications even though the energy gap between the CO and FM phases is small. Recently, nanosized manganites were synthesized and some exotic phenomena associated with the size effect were observed. 5,6,7,8,9,10,11,12,13 One of the most important observations was that the robust charge ordering in bulk manganites was weakened in both nanoparticles and nanowires, accompanied with an appearance of weak ferromagnetism. 5,6,7,8,12,13 Additionally, our experiments showed that the charge ordering observed in bulk La 1/3 Sr 2/3 FeO 3 can be suppressed in nanoparticles.14 An earlier explanation on the size effect in nanosized FM La 0.7 Ca 0.3 MnO 3 , 11 which attributed the enhancement of ferromagnetism to the contraction of lattice volume, seems not applicable to nanosized CO manganites where slight expansion of the lattice volume was observed. 5,6Therefore, an alternative explanation seems to be required for understanding the size effect in nanosized CO manganites.In this Letter, a phenomenological model based on the surface PS state is proposed. Here the CO phase is specified as the CE-type CO phase, which is the common ground state in the half-doped (T 1/2 D 1/2 MnO 3 ) narrow bandwidth manganites.15 In the CE ground state, Mn cations form FM zigzag chains in X-Y plane, with antiferromagnetic (AFM) couplings between the neighboring chains in X-Y plane and neighboring sites along Z axis.16 For...

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“…In addition, it is well known that perovskite oxides may be sensitive to external factors. [6][7][8] For example, recently the use of epitaxial strain has attracted great attentions due to many unexpected effects on thin films, [8][9][10][11][12] which has been proved to be a useful route to design potential devices.…”

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confidence: 99%

Magnetic orders of LaTiO3 under epitaxial strain: A first-principles study

Weng¹,

Huang²,

Tang³

et al. 2014

Journal of Applied Physics

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Perovskite LaTiO 3 bulk is a typical Mott-insulator with G-type antiferromagnetic order. In this work, the biaxial strain effects on the ground magnetic order of LaTiO 3 films grown on various substrates have been studied. For the compressive strain, LaTiO 3 films grown on LaAlO 3 , LaGaO 3 , and SrTiO 3 substrates undergo a phase transition from the original G-type antiferromagnet to A-type antiferromagnet. The underlying physical mechanisms are the lattice distortions tunned by strain. While for the tensile strain, the BaTiO 3 and LaScO 3 substrates have been tested, which show a tendency to transit the LaTiO 3 to the C-type antiferromagnet. Furthermore, our calculations find that the magnetic transitions under epitaxial strain do not change the insulating fact of LaTiO 3 .Perovskite oxides ABO 3 have attracted continuing attention and been intensively investigated due to their novel physical properties and a broad range of technical applications. 1 Among abundant perovskite compounds, the canonical Mott insulator RTiO 3 (R 3+ denotes a rareearth ions) are physically interesting due to the complex couplings between the orbital, spin, lattice degrees of freedom of Ti's 3d electron which is localized by the strong Coulombic interaction. In RTiO 3 perovskites, the ligand crystal field from the oxygen octahedron splits the 5-fold 3d levels into two groups: the 3-fold t 2g orbitals and the 2-fold e g orbitals. The Fermi level is located in the t 2g levels, and the t 2g orbitals are highly localized due to the p-d hybridization. Moreover, the GdFeO 3 -type structure distortions, which combine the tilts and rotations of the oxygen octahedrons, are prominent in the orthorhombic RTiO 3 . According to previous studies, 2-4 the ground magnetic phase of RTiO 3 transits from the ferromagnetism to G-type antiferromagnetism, with increasing size of R or in other words with weaking GdFeO 3 -type distortions, 5 as shown in Fig. 1(a).In the RTiO 3 bulks, compounds with small GdFeO 3 -type distortions exhibit the G-type antiferromagnetic (AFM) ordering, e.g. LaTiO 3 , and the large ones tend to lead the FM ordering, e.g. YTiO 3 . In addition, it is well known that perovskite oxides may be sensitive to external factors. 6-8 For example, recently the use of epitaxial strain has attracted great attentions due to many unexpected effects on thin films, 8-12 which has been proved to be a useful route to design potential devices.In this work, the effects of epitaxial strain on the ground magnetic order of LaTiO 3 films will be studied using the first-principles calculations, as illustrated in Fig. 1(b). Our calculations predict that a robust Atype AFM phase can be stabilized by the compressive strain. In contrast, LaTiO 3 films remain G-type AFM under moderate tensile strain, but have a tendency to become the C-type AFM with further increasing the tensile strain. LaTiO 3 has the orthorhombic structure (space group Pbnm) 9,13 with the experimental lattice constants of a=5.636Å, b=5.618Å, and c=7.916Å, containing 4 formula units. 14 In t...

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Jahn-Teller distortion induced charge ordering in the CE phase of manganites

Cited by 19 publications

References 25 publications

Relationship between orbital structure and lattice distortions in Jahn-Teller systems

Relationship between orbital structure and lattice distortions in Jahn-Teller systems

Surface phase separation in nanosized charge-ordered manganites

Magnetic orders of LaTiO3 under epitaxial strain: A first-principles study

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