New perovskite-based manganite Pb2Mn2O5

The microstructure of the charge/orbital ordering Ruddleden-Popper phase PrCa 2 Mn 2 O 7 was studied by transmission electron microscopy along both the [001] and the [110] orientation. Three coexisting charge/orbital ordering phases CO1, CO2, and CO3 were observed along the [001] orientation at room temperature. Different from the one-dimensional modulation in the CO1 and CO2 phase, the CO3 phase is characterized by two sets of mutually perpendicular structural modulations. From [110] high angle annular dark field-scanning transmission electron microscopy, we found that the Pr atoms locate in-between the bilayer MnO 6 octahedra, which is different from the previous reports. The strongly correlated electronic systems of perovskite manganites have received great attention because of their fascinating physical properties such as colossal magnetoresistance and high spin polarity, which could find potential applications in spintronics or magnetic tunnel junction. [1][2][3][4][5][6][7][8][9] The physical mechanism of these properties was ascribed to the complicated interplays between the four degrees of freedom of lattice, charge, orbital, and spin, and the consequent ordering as well as possible phase separation. 6,[10][11][12] Recently, two distinct charge/orbital ordering (CO/OO) states were found in the Ruddlesden-Popper (RP) compound Pr(Sr 1Àx Ca x ) 2 Mn 2 O 7 . 13 Pr(Sr 1Àx Ca x ) 2 Mn 2 O 7 has a layer structure (AO) (ABO 3 ) n (n ¼ 2), where two (ABO 3 ) perovskite layers are separated by a AO rock salt layer along the long axis. The two reported CO/OO phases in Pr(Sr 0.1 Ca 0.9 ) 2 Mn 2 O 7 are the high-temperature phase CO1 phase at 330 K > T > 295 K (lattice parameters a ¼ 0.5412, b ¼ 1.0921, c ¼ 1.9234 nm, and space group Pbnm) and the lower-temperature CO2 phase at T < 295 K (a ¼ 1.0812, b ¼ 0.5475, c ¼ 1.9203 nm, and space group Am2m, Ref. 13). The CO1 phase is centrosymmetric without any spontaneous electric polarization, but the CO2 phase is a noncentrosymmetric phase with spontaneous electric polarization. 13 The thermally induced rotation of orbital stripes between these two ordering phases has attracted extensive interest. [14][15][16][17][18] However, the limited information about its microstructures has obstructed a better understanding of the macro properties and physics underneath. Therefore, we carried out a transmission electron microscopy (TEM) study on PrCa 2 Mn 2 O 7 to reveal the different aspects of the microstructure. The phases and micro domains viewed along the [001] zone axis are discussed. The heavy Pr atoms were found to locate inbetween the bilayer MnO 6 octahedra.Bulk PrCa 2 Mn 2 O 7 samples were synthesized using a traveling solvent floating zone method with high oxygen background pressure. 17,18 Powdered samples, deposited on a Cu grid coated with a holey carbon film, as well as Ar-ion milled TEM samples were used for TEM investigation. A Tecnai G 2 electron microscope equipped with a Gatan cooling and heating holder operated at 200 kV was used to record electron diffractio...

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“…[23][24][25][26][27][28][29][30][31][32][33][34][35] Fig. 4(a) is a [001] HRTEM image of the CO1 phase.…”

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confidence: 99%

Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering

Tian

Deng

et al. 2013

Applied Physics Letters

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“…An interesting feature about this series is the magnetic frustration at the crystallographic shear plane separating the perovskite blocks, due to competing FM and AFM interactions. [2] Also incommensurately modulated perovskites can be obtained, for example (Pb,Bi)1-xFe1+xO3-y. These arise by 3+ 2+ replacing Biwith Pb, which introduces an oxygen deficiency, which is then accommodated by periodically spaced CS planes to reduce the coordination of the A-cations at the interface.…”

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confidence: 99%

New modular oxide structures through the use of lone-pair cations as 'chemical scissors'

Hadermann¹,

Batuk²,

Batuk³

et al. 2013

Acta Cryst Sect A

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“…The oxygen K edge of MnO has been published in a number of papers [363,387,390,[436][437][438][439][440][441][442]. MnO is sensitive to the x-ray and electron beams of the XAS and EELS measurements and also MnO is sometimes modified by defects; some MnO samples are deliberately doped with defects, for example the MnO(1%Li) sample [437].…”

Section: Manganese Oxidesmentioning

confidence: 99%

“…The e g state is half occupied creating a Jahn-Teller ground state implying significant site distortions. The oxygen K edge of Mn 2 O 3 has been published in a number of papers [390,436,438,440,441]. The oxygen K edge has three peaks that can be assigned respectively to e g -up, t 2g -down and e g -down.…”

Section: Manganese Oxidesmentioning

confidence: 99%

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Oxygen K-edge X-ray Absorption Spectra

Frati¹

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New perovskite-based manganite Pb2Mn2O5

Cited by 12 publications

References 19 publications

Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering

Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering

New modular oxide structures through the use of lone-pair cations as 'chemical scissors'

Oxygen K-edge X-ray Absorption Spectra

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