Features of the intermediate state appearing between the C- and A-type orbital-ordered states in the highly-correlated electronic system Sr1-xNdxMnO3

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 603-608 ◽  
Author(s):  
Ayumi Shiratani ◽  
Hiroki Sato ◽  
Yasuhide Inoue ◽  
Yasumasa Koyama
Keyword(s):  
Electronic System ◽  
Oxide System ◽  
The State ◽  
State Change ◽  
Orbital Ordering ◽  
Type Orbital ◽  
Transmission Electron ◽  
Displacement Pattern ◽  
Highly Correlated ◽  
Image Position

ABSTRACTThe presence of the C- and A-type orbital-ordered states has been reported in the highly-correlated electronic system Sr1-xNdxMnO3 (SNMO). The interesting feature of the oxide system is that an increase in the Nd content leads to the (C-type → A-type) state change across a temperature-independent morphotropic phase boundary (MPB). Although structural fluctuations can be expected near the MPB, the detailed features of the state change have not been understood sufficiently. Thus, the crystallographic features of the state change in SNMO with 0.35 ≤ x ≤ 0.49 have been investigated mainly at 300 K, by x-ray powder diffraction and transmission electron microscopy. It was found that the C-type orbital-ordered state with the tetragonal-I4/mcm symmetry and the disordered orthorhombic-Imma state were present for 0.35 ≤ x ≤ 0.43 and for 0.45 ≤ x ≤ 0.49 at 300 K, respectively. The notable feature of the state change is that disordered regions with the cubic-Pm$\bar 3$ m symmetry were also found locally for x = 0.43, in addition to the C-type state. Because the rotational-displacement pattern for oxygen octahedra involved in the disordered-Imma state is the same as that in the A-type state, furthermore, the former disordered state may be regarded as a precursor state to the A-type orbital ordering.

Crystallographic Features of the C-Type Orbital-Ordered, and Charge- and Orbital-Ordered States in the Simple Perovskite Manganite Ca1-xLaxMnO3

2012 ◽  
Vol 706-709 ◽  
pp. 1612-1617
Author(s):  
Yasuhide Inoue ◽  
Masazumi Arao ◽  
Daisuke Shiga ◽  
Yasumasa Koyama
Keyword(s):  
Three Dimensional ◽  
Electronic System ◽  
Lattice System ◽  
Perovskite Manganite ◽  
Orbital Ordering ◽  
Transverse Lattice ◽  
Type Orbital ◽  
Antiferromagnetic Ordering ◽  
Monoclinic Distortion ◽  
Highly Correlated

The C-type orbital-ordered (CTOO), and charge-and orbital-ordered (COO) states are present in the simple perovskite manganite Ca1-xLaxMnO3, which has a three-dimensional highly-correlated electronic system. In this study, the crystallographic features of the CTOO and COO states have been investigated mainly by transmission electron microscopy to understand responses of a lattice system to these orderings. Of these two states, the cooling from the disordered orthorhombic Pnma (DO) state around x = 0.20 resulted in the CTOO state with the monoclinic P21/m symmetry. As a result of the monoclinic distortion as a response of the lattice system, the CTOO state consisted of a banded structure that was characterized by an alternating array of two monoclinic domains with different β values. In 0.30 < x < 0.50, on the other hand, the appearance of the COO state from the DO state on cooling accompanied a transverse lattice modulation with q = []DO as a response to orbital ordering in the COO state. The subsequent cooling in the COO state led to the antiferromagnetic ordering with a large lattice dilatation. In other words, no change in the crystal symmetry occurs in the appearance of the antiferromagnetic ordering.

Features of Electronic States in the Highly-Correlated Electronic System Sr1-xNdxMnO3 around x = 0.50

2016 ◽  
Vol 879 ◽  
pp. 1766-1771 ◽  
Author(s):  
Rina Shimasaki ◽  
Ayumi Shiratani ◽  
Hiroki Sato ◽  
Yasuhide Inoue ◽  
Yasumasa Koyama
Keyword(s):  
Electronic States ◽  
Electronic System ◽  
Electron System ◽  
The State ◽  
Charge Ordering ◽  
Type Orbital ◽  
Charge Modulations ◽  
Highly Correlated ◽  
A Charge ◽  
Ordered State

In the highly-correlated electron system Sr1-xNdxMnO3 (SNMO) having the simple perovskite structure, there are interesting electronic states, which are related to degrees of charge, orbital, and spin freedoms for eg electrons in Mn ions. Among these states, in the case of SNMO, the C-, A-and CE-type antiferromagnetic states were reported for 0.20 ≤ x ≤ 0.38, for 0.38 ≤ x ≤ 0.48, and for 0.48 ≤ x ≤ 0.52, respectively. The points to note here are that these antiferromagnetic states are directly associated with corresponding orbital orderings, and that the CE-type state also accompanies charge ordering. Because of these features, we were interested in the (A → CE) state change in SNMO. The crystallographic features of prepared SNMO samples with 0.46 ≤ x ≤ 0.50 have thus been investigated mainly by means of a transmission electron microscope equipped with a low-temperature holder. As a result, the state around 100 K for x = 0.48 was first understood to be identified as the Imma state, which includes a large number of orbital-modulated (OM) regions with an average size of about 10 nm. The feature of such regions is that the orbital modulation has an incommensurate periodicity and a charge modulation is absent in them. On the other hand, the CE-type state having the commensurate orbital and charge modulations was also confirmed to be present for x = 0.50. In addition to these two states, the state around 100 K for x = 0.46 was found to be characterized by the coexistence state consisting of the C-type orbital-ordered state and the Imma states including OM regions. In other words, the presence of the A-type orbital-ordered state could not be confirmed in the temperature range between 300 K and about 100 K for 0.46 ≤ x ≤ 0.50 in this study.

Formation of the C-type Orbital-Ordered State in the Simple Perovskite Manganite Sr1-xSmxMnO3

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 615-620 ◽  
Author(s):  
Misato Yamagata ◽  
Ayumi Shiratani ◽  
Yasuhide Inoue ◽  
Yasumasa Koyama
Keyword(s):  
Electronic System ◽  
The State ◽  
Tetragonal Symmetry ◽  
Perovskite Manganite ◽  
Orbital Ordering ◽  
Teller Distortion ◽  
Rotational Displacement ◽  
Type Orbital ◽  
Jahn Teller ◽  
Jahn Teller Distortion

ABSTRACTThe simple perovskite manganite Sr1-xSmxMnO3 (SSMO) has been reported to have a highly-correlated electronic system for eg-electrons in a Mn ion. According to the previous studies, the C-type orbital-ordered (COO) state with the I4/mcm symmetry was found to be formed from the disordered-cubic (DC) state on cooling. The feature of the COO state is that its crystal structure involves both the Jahn-Teller distortion to orbital ordering and the R25-type rotational displacement of oxygen octahedra. Because of the involvement of both the distortion and the displacement, their competition should be expected in the formation of the COO state. However, the detailed features of the competition have not been understood yet. Thus, the crystallographic features of the COO state in SSMO have been examined by x-ray powder diffraction and transmission electron microscopy. It was found that, when the Sm content increased from x = 0 at room temperature, the DC state changed into the COO state with the tetragonal symmetry around x = 0.13. The notable feature of the COO state is that the state is characterized by a nanometer-scaled banded structure consisting of an alternating array of two tetragonal bands. One tetragonal band consisted of the COO state involving both the Jahn-Teller distortion and the R25-type rotational displacement. But, there was only the latter displacement in the other, the state of which could be identified as a disordered tetragonal (DT) state. Based on this, it is understood that the COO-state formation from the DC state should take place via the appearance of the DT state, which may involve fluctuations of the C-type orbital ordering.

Crystallographic Features of the Charge-Orbital-Ordered State in the Highly-Correlated Electronic System Ca1-xPrxMnO3

2014 ◽  
Vol 922 ◽  
pp. 376-382
Author(s):  
Kentaro Kojima ◽  
Yasuhide Inoue ◽  
Masazumi Arao ◽  
Yasumasa Koyama
Keyword(s):  
Electronic System ◽  
Careful Analysis ◽  
The State ◽  
Transverse Lattice ◽  
Antiferromagnetic Ordering ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Highly Correlated ◽  
A Charge ◽  
Content Range

The charge-exchange-type orbital-ordered (CEOO) state accompanying antiferromagnetic ordering has been reported in the highly-correlated electronic system Ca1-xPrxMnO3(CPMO) with the simple perovskite structure. The feature of the CEOO state in CPMO is that the state is present in the wide Pr-content range of 0.30 ≤x≤ 0.70. Although the Zener-polaron model was proposed for the CEOO state atx= 0.60, the detailed features of the CEOO state, particularly for lower Pr contents, have not been understood sufficiently. We have thus investigated the crystallographic features of the CEOO state in CPMO with 0.40 ≤x≤ 0.50, mainly by transmission electron microscopy. It was found that, when the temperature was lowered from the disordered state, incommensurate satellite reflections characterizing the CEOO state appeared in electron diffraction patterns below about 250 K in CPMO. The careful analysis of the reflections indicated that the CEOO state for 0.40 ≤x≤ 0.45 was different from that for 0.45 ≤x≤ 0.50. Concretely, the former CEOO state accompanied only a transverse lattice modulation, while both transverse and longitudinal modulations with different wave vectors appeared in the latter state. This implies that the state for 0.40 ≤x≤ 0.45 can be regarded as an orbital-modulated (OM) state without a charge modulation. It is thus understood that an increase in the Pr content leads to the OM-to-CEOO state change below about 250 K aroundx= 0.45.

Crystallographic Features of the A-Type and CE-Type Antiferromagnetic States in the Simple-Perovskite Manganite System Sr1-xNdxMnO3

2011 ◽  
Vol 409 ◽  
pp. 532-537
Author(s):  
Yusuke Onezawa ◽  
Yasuhide Inoue ◽  
Masazumi Arao ◽  
Yasumasa Koyama
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Electronic System ◽  
Paramagnetic State ◽  
Heating Process ◽  
In Situ Observation ◽  
Perovskite Manganite ◽  
Transmission Electron ◽  
Highly Correlated

The electronic states of Sr1-xNdxMnO3 with the simple perovskite structure are characterized by a three-dimensional highly-correlated electronic system. To understand the detailed features of the A-and CE-type antiferromagnetic states in this system, their crystallographic features for x = 0.47, 0.48, and 0.50 have been investigated mainly by both x-ray powder diffraction and transmission electron microscopy. It was found at room temperature that the crystal structure for x = 0.47 was determined to have the monoclinic C2/m symmetry, while the orthorhombic Imma structure was confirmed for x = 0.48 and 0.50. The in-situ observation for x = 0.47 indicated that, in the heating process from room temperature, the C2/m-to-Imma transition occurred in the paramagnetic state, and that the A-type antiferromagnetic state appeared below about 200 K on cooling. In addition, the cooling from room temperature for x = 0.48 and 0.50 resulted in the direct transitions from the orthorhombic Imma state to the A-and CE-type antiferromagnetic states, respectively. Based on these features, we simply discussed the physical origin of the appearance of the paramagnetic state with the monoclinic symmetry for x = 0.47.

Possible Orbital-Ordered State in the Highly-Correlated Electronic Material Sr1-xCexMnO3

2014 ◽  
Vol 922 ◽  
pp. 230-236
Author(s):  
Takehiro Hanaoka ◽  
Yasuhide Inoue ◽  
Yasumasa Koyama
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Electronic System ◽  
Careful Analysis ◽  
Perovskite Manganite ◽  
Orbital Ordering ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Diffraction Patterns ◽  
Highly Correlated

The simple perovskite manganite Sr1-xCexMnO3 (SCMO) has a highly-correlated electronic system with a three-dimensional character. Because the presence of orbital-ordered states of eg electrons can be expected in SCMO, the crystallographic features of SCMO samples with 0.09 ≤ x ≤ 0.20 have been investigated mainly by transmission electron microscopy. In addition to fundamental reflections due to the simple perovskite structure, their electron diffraction patterns at room temperature exhibited both the presence of superlattice reflections at k = ()c in the cubic notation and the splitting of fundamental and superlattice reflections. The careful analysis of these reflections indicated that the superlattice reflections originated from the R25-type rotational displacement of oxygen octahedra about one of the <100>c directions. On the other hand, the splitting of the reflections was found to be due to a {110}c banded structure consisting of two tetragonal bands with different c/a values.　Because one of two tetragonal bands had the c/a value of about 1.028, the splitting reflects the introduction of the Jahn-Teller distortion as a response of a lattice system to orbital ordering. It is thus understood that the C-type orbital ordering of eg electrons should be involved in the state at room temperature for 0.09 ≤ x ≤ 0.20 in SCMO.

Crystallographic features of orbital ordering related to the C-type antiferromagnetic state in the simple perovskite manganite Ca1-xPrxMnO3

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 579-584 ◽  
Author(s):  
Kentaro Kojima ◽  
Yasuhide Inoue ◽  
Yasumasa Koyama
Keyword(s):  
State Formation ◽  
Powder Diffraction ◽  
Electronic System ◽  
Perovskite Manganites ◽  
Perovskite Manganite ◽  
Orbital Ordering ◽  
X Ray ◽  
Notable Feature ◽  
Type Orbital ◽  
Antiferromagnetic Ordering

ABSTRACTIn the highly-correlated electronic system Ca1-xPrxMnO3 having the simple perovskite structure, it has been reported that there exists the C-type orbital-ordered (COO) state accompanying an antiferromagnetic ordering for 0.10 ≤ x ≤ 0.25. According to the previous studies concerning orbital-ordered states in simple perovskite manganites, the COO state was understood to be characterized by a spatial array of (3z2-r2)-type orbitals for 3d electrons in Mn ions. The notable feature of the COO state in Ca1-xPrxMnO3 is that the state with the monoclinic-P21/m symmetry appears as a result of the structural transition from the disordered state with the orthorhombic-Pnma symmetry. Compared with the COO-state formation from the cubic-Pm$\overline 3$m state, however, the formation from the disordered-Pnma state has not been understood yet. We have thus examined the crystallographic features of the formation of the COO state in Ca1-xPrxMnO3, mainly by x-ray powder diffraction and transmission electron microscopy. In the case of x = 0.16, for instance, the COO state was found to appear from the disordered-Pnma state around 90 K on cooling. The notable feature of the formation is that, in the Pnma state just before the COO-state formation, characteristic diffuse scattering appeared around each reflection in electron diffraction patterns, together with the splitting of the 200c reflection in x-ray powder diffraction profiles in the pseudo-cubic notation. Based on these experimental data, it is understood that the formation of the COO state in Ca1-xPrxMnO3 accompanies remarkable fluctuations of the C-type orbital ordering in the disordered-Pnma state.

Crystallographic Features of the State Appearing in the Multiferroic Material Bi1-xLaxFeO3 around x = 0.20

2016 ◽  
Vol 879 ◽  
pp. 2222-2227
Author(s):  
Haruka Yoshida ◽  
Masashi Nomoto ◽  
Takumi Inoshita ◽  
Yasuhide Inoue ◽  
Yoichi Horibe ◽  
...  
Keyword(s):  
Mixed Oxide ◽  
Reciprocal Lattice ◽  
Oxide System ◽  
The State ◽  
Oxide Systems ◽  
Modulated Structure ◽  
Transmission Electron ◽  
Multiferroic Bifeo ◽  
Structure State ◽  
State Boundary

The simple-perovskite system Bi1-xLaxFeO3 (BLFO) is one of mixed-oxide systems having the multiferroic BiFeO3 as an end material, which shows the ferroelectric and antiferromagnetic orders in its ground state. Because of the paraelectric nature of LaFeO3 as another end material, the ferroelectric-to-paraelectric state change can be expected to occur in the mixed-oxide system BLFO. The interesting feature of BLFO is that there are both the PbZrO3-type and incommensurately modulated (IM) states in the intermediate La-content range between the ferroelectric-R3c and paraelectric-Pnma states. Although the detailed features of these two states have not been understood sufficiently, in this study, we focus on the IM state around x = 0.20, and have investigated the crystallographic features of prepared BLFO samples with 0.15 ≤ x ≤ 0.35, mainly by transmission electron microscopy. It was found that six kinds of superlattice reflections were, for instance, present in the reciprocal lattice of the state at 300 K for x = 0.20, in addition to fundamental reflections due to the cubic simple-perovskite structure. To understand the appearance of these superlattice reflections, we regarded the state as a modulated-structure state in this study. Concretely, the modulated structure was assumed to be characterized by the appearance of both the incommensurate wave with qI = <1/(4+δ) 1/(4+δ) 0>c and the commensurate wave with qII = <1/4 0 0>c in the normal-Imma structure. In addition, the appearance of the two modulation waves could also produce the superlattice reflections at the <1/4 1/4 1/4>c-, <1/2 0 0>c-, and <1/2 1/2 0>c-type positions in the reciprocal lattice. From the comparison with the experimental data obtained in this study, our modulated-structure model seems to be appropriate for the IM state in the vicinity of the PbZrO3-type/IM state boundary.

A Magnetic Spectrometer for a Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 436-437
Author(s):  
A. Kosiara ◽  
J. W. Wiggins ◽  
M. Beer
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Magnetic Spectrometer ◽  
Fringe Field ◽  
Curvature Radius ◽  
Magnetic Pole ◽  
Quadrupole Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Under Construction ◽  
Image Position

A magnetic spectrometer to be attached to the Johns Hopkins S. T. E. M. is under construction. Its main purpose will be to investigate electron interactions with biological molecules in the energy range of 40 KeV to 100 KeV. The spectrometer is of the type described by Kerwin and by Crewe Its magnetic pole boundary is given by the equationwhere R is the electron curvature radius. In our case, R = 15 cm. The electron beam will be deflected by an angle of 90°. The distance between the electron source and the pole boundary will be 30 cm. A linear fringe field will be generated by a quadrupole field arrangement. This is accomplished by a grounded mirror plate and a 45° taper of the magnetic pole.

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

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