1000% colossal magnetoresistance at room temperature in the A-site ordered perovskite manganites, Sm1−xLax+yBa1−yMn2O6

2005 ◽  
Vol 98 (4) ◽  
pp. 046108 ◽  
Author(s):  
Tomohiko Nakajima ◽  
Yutaka Ueda
Keyword(s):  
Colossal Magnetoresistance ◽  
Room Temperature ◽  
Perovskite Manganites ◽  
A Site

scholarly journals Investigation of Lattice Effects in Rare Earth Manganites by 18O-isotope Exchange

1999 ◽  
Vol 52 (2) ◽  
pp. 235 ◽  
Author(s):  
R. Mahesh ◽  
M. Itoh
Keyword(s):  
Rare Earth ◽  
Colossal Magnetoresistance ◽  
Charge Ordering ◽  
Perovskite Manganites ◽  
Lattice Effects ◽  
Jahn Teller ◽  
18O Isotope ◽  
Ionic Size ◽  
Rare Earth Manganites ◽  
A Site

The strong coupling between the electron spin and lattice arising from the Jahn-Teller effect of manganese ions plays an important role in the mechanism of colossal magnetoresistance and related properties of the rare earth manganites. The lattice effects in this class of oxides have been extensively studied through the application of hydrostatic as well as chemical pressures and magnetic fields. The recently observed giant 18O isotope effect provides direct evidence for the formation of lattice polarons in manganites. Here we report the preliminary results of our investigations on a variety of normal as well as 18O isotope-exchanged perovskite manganites exhibiting colossal magnetoresistance and charge ordering. The observed isotope shift of Tc as well as that of Tco is correlated with the key parameters controlling the lattice such as the Mn 3+ content, the average ionic radius of the A-site cation ⟨rA⟩ , and the A-site ionic size disorder σ2 .

scholarly journals Effect of the Grain Size on the Magnetic Phase Separation in La0.8Sr0.2MnO3 by Magnetic Force Microscopy

2012 ◽  
Vol 18 (S5) ◽  
pp. 101-102
Author(s):  
P. De Sousa ◽  
N. Panwar ◽  
I. Bdikin ◽  
A. L. Kholkin ◽  
C. M. Fernandes ◽  
...  
Keyword(s):  
Grain Size ◽  
Phase Separation ◽  
Colossal Magnetoresistance ◽  
Room Temperature ◽  
Magnetic Phase ◽  
Magnetic Domain ◽  
Charge Ordering ◽  
Perovskite Manganites ◽  
Fundamental Study ◽  
Metallic Clusters

Perovskite manganites have been the focus of worldwide research during the last two decades because of the observation of colossal magnetoresistance (CMR) effect. These materials have potential applications in magnetic field sensors, spin filters, infrared bolometers and cathodes for solid oxide fuel cells. Such manganites are also important from the fundamental study viewpoint as they offer interplay among various degrees of freedom viz. spin, lattice and charge ordering. Moreover, phase separation may occur in manganites with low concentration of the dopant. In such scenario, ferromagnetic metallic clusters are embedded in antiferromagnetic insulating matrix. The fraction of these magnetic phases may vary from the nano- to micro-scale. With higher dopant concentration, the percolation of these magnetic metallic clusters leads to the apparent CMR effect. In this study we focus our attention to the low doped La0.8Sr0.2MnO3 (LSMO) manganite and investigate the possible magnetic phase separation and effect of variation in grain size on the magnetic domain size. La0.8Sr0.2MnO3 possesses Curie temperature (TC) higher than room temperature, therefore the material is supposed to be in the magnetic state at room temperature.

Transition Insulator-Metal and Antiferromagnetic-Paramagnetic Cu Doped in La0.47Ca0.53MnO3

2015 ◽  
Vol 1123 ◽  
pp. 73-77 ◽  
Author(s):  
Yohanes Edi Gunanto ◽  
K. Sinaga ◽  
B. Kurniawan ◽  
S. Poertadji ◽  
H. Tanaka ◽  
...  
Keyword(s):  
High Resolution ◽  
Low Temperature ◽  
Magnetic Structure ◽  
Room Temperature ◽  
Paramagnetic Phase ◽  
Perovskite Manganites ◽  
Antiferromagnetic Phase ◽  
Temperature Transition ◽  
Cu Doping ◽  
Metal State

The study of the perovskite manganites La0.47Ca0.53Mn1-xCuxO3 with x = 0, 0.06, 0.09, and 0.13 has been done. The magnetic structure was determined using high-resolution neutron scattering at room temperature and low temperature. All samples were paramagnetic at room temperature and antiferromagnetic at low temperature. Using the SQUID Quantum Design, the samples showed that the doping of the insulating antiferromagnetic phase La0.47Ca0.53MnO3 with Cu doping resulted in the temperature transition from an insulator to metal state, and an antiferromagnetic to paramagnetic phase. The temperature transition from an insulator to metal state ranged from 23 to 100 K and from 200 to 230 K for the transition from an antiferromagnetic to paramagnetic phase.

The rich physics of A-site-ordered quadruple perovskite manganites AMn7O12

2021 ◽  
Author(s):  
Alexei A. Belik ◽  
Roger D Johnson ◽  
Dmitry Khalyavin
Keyword(s):  
Perovskite Structure ◽  
Double Exchange ◽  
Perovskite Manganites ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Jahn Teller ◽  
The Rich ◽  
A Site ◽  
Small Polarons

Perovskite-structure AMnO3 manganites played an important role in the development of numerous physical concepts such as double exchange, small polarons, electron-phonon coupling, and Jahn−Teller effects, and they host a variety...

scholarly journals Physical and Topological Properties of Circular DNA

1966 ◽  
Vol 49 (6) ◽  
pp. 103-125 ◽  
Author(s):  
Jerome Vinograd ◽  
Jacob Lebowitz'
Keyword(s):  
Room Temperature ◽  
Melting Behavior ◽  
Neutral Salt ◽  
Winding Number ◽  
Complementary Strand ◽  
Circular Dna ◽  
Tumor Viruses ◽  
Weakly Closed ◽  
A Site ◽  
Melting Experiments

Several types of circular DNA molecules are now known. These are classified as single-stranded rings, covalently closed duplex rings, and weakly bonded duplex rings containing an interruption in one or both strands. Single rings are exemplified by the viral DNA from ϕX174 bacteriophage. Duplex rings appear to exist in a twisted configuration in neutral salt solutions at room temperature. Examples of such molecules are the DNA's from the papova group of tumor viruses and certain intracellular forms of ϕX and λ-DNA. These DNA's have several common properties which derive from the topological requirement that the winding number in such molecules is invariant. They sediment abnormally rapidly in alkaline (denaturing) solvents because of the topological barrier to unwinding. For the same basic reason these DNA's are thermodynamically more stable than the strand separable DNA's in thermal and alkaline melting experiments. The introduction of one single strand scission has a profound effect on the properties of closed circular duplex DNA's. In neutral solutions a scission appears to generate a swivel in the complementary strand at a site in the helix opposite to the scission. The twists are then released and a slower sedimenting, weakly closed circular duplex is formed. Such circular duplexes exhibit normal melting behavior, and in alkali dissociate to form circular and linear single strands which sediment at different velocities. Weakly closed circular duplexes containing an interruption in each strand are formed by intramolecular cyclization of viral λ-DNA. A third kind of weakly closed circular duplex is formed by reannealing single strands derived from circularly permuted T2 DNA. These reconstituted duplexes again contain an interruption in each strand though not necessarily regularly spaced with respect to each other.

Giant magnetoimpedance and colossal magnetoresistance in La[sub 0.75]Sr[sub 0.25]MnO[sub 3] at room temperature

2002 ◽  
Vol 91 (12) ◽  
pp. 10003 ◽  
Author(s):  
Hongwei Qin ◽  
Jifan Hu ◽  
Juan Chen ◽  
Yizhong Wang ◽  
Zhenxi Wang
Keyword(s):  
Colossal Magnetoresistance ◽  
Room Temperature ◽  
Giant Magnetoimpedance

Phase Diagram of the W-doped Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 System Around a Morphotropic Phase Boundary Composition

2002 ◽  
Vol 17 (5) ◽  
pp. 1085-1091 ◽  
Author(s):  
W. Z. Zhu ◽  
M. Yan ◽  
A. L. Kholkin ◽  
P. Q. Mantas ◽  
J. L. Baptista
Keyword(s):  
High Temperature ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical Neutrality ◽  
Phase Boundary Composition ◽  
A Site ◽  
Successive Phase

The morphotropic phase boundary (MPB) composition that is characterized by the coexistence of rhombohedral and tetragonal phases in the Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 system was modified by W-doping at the B site of a perovskite structural block. To maintain the electrical neutrality, creation of A-site vacancies was intentionally introduced in the formulation of the examined compositions. Incorporation of W ions was revealed to stabilize the tetragonal phase against the rhombohedral one, shifting the MPB toward the PZN-rich end at room temperature. High-temperature x-ray diffraction examination in combination with dielectric measurements discloses two successive phase transitions as a sample is cooled from high temperature, namely, paraelectric cubic to ferroelectric rhombohedral followed by ferroelectric rhombohedral to ferroelectric tetragonal. W addition appears to suppress the first transition while promoting the second one.

A-site K-doping to enhance room-temperature TCR of polycrystalline La0.8Sr0.2-K MnO3 ceramics

2020 ◽  
Vol 847 ◽  
pp. 156417
Author(s):  
Hongjiang Li ◽  
Kaili Chu ◽  
Xingrui Pu ◽  
Shuai Zhang ◽  
Gang Dong ◽  
...  
Keyword(s):  
Room Temperature ◽  
A Site

A-Site Distribution in La1−xSrxMnO3: a Computational Study

2008 ◽  
Vol 1074 ◽  
Author(s):  
Yun Hee Jang ◽  
François Gervais ◽  
Yves Lansac
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Colossal Magnetoresistance ◽  
Computational Study ◽  
Mixed Valence ◽  
Magnetic Tunnel Junction ◽  
Md Simulations ◽  
Site Distribution ◽  
Mixed Valence Manganites ◽  
A Site

ABSTRACTThe possibility of an A-site (La3+/Sr2+) ordering in a colossal magnetoresistance manganite (CMR) La3/4Sr1/4MnO3 was explored using molecular dynamics (MD) simulations with a newly developed force field (FF) and quantum mechanics (QM) calculations on the structures obtained from MD. The calculated degrees of stabilization (enthalpy gain) of various patterns of A-site ordering are not significant enough to overcome the accompanying entropy loss, supporting the random A-site distribution in La3/4Sr1/4MnO3. This approach combining MD and QM as well as the versatile FF developed in this study should be useful to investigate the structures and functions of magnetic tunnel junction devices involving mixed-valence manganites.

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