scholarly journals Magnetic-Field-Induced Suppression of Jahn-Teller Phonon Bands in (La0.6Pr0.4)0.7Ca0.3MnO3: the Mechanism of Colossal Magnetoresistance shown by Raman Spectroscopy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
S. Merten ◽  
O. Shapoval ◽  
B. Damaschke ◽  
K. Samwer ◽  
V. Moshnyaga
Keyword(s):  
Magnetic Field ◽  
Raman Spectroscopy ◽  
Colossal Magnetoresistance ◽  
Jahn Teller

STUDY OF MAGNETIZATION IN MANGANITE SYSTEM IN THE PRESENCE OF LATTICE DISTORTION

2006 ◽  
Vol 20 (15) ◽  
pp. 2093-2116 ◽  
Author(s):  
G. C. ROUT ◽  
N. PARHI ◽  
S. N. BEHERA
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Colossal Magnetoresistance ◽  
Lattice Distortion ◽  
Zeeman Splitting ◽  
Model Parameters ◽  
Coupling Constant ◽  
Magnetic Exchange ◽  
Magnetic Exchange Coupling ◽  
Jahn Teller

The manganites of the type Re1-xAxMnO3( Re = La , Nd , A = Ca , Sr , Ba ) are believed to be half metallic magnets exhibiting colossal magnetoresistance (CMR). The manganite system is described by a simple model Hamiltonian consisting of the hopping of the itinerant d-electrons in the doubly degenerate egband of Mn ions which is split by a static J-T lattice distortion due to band Jahn-Teller (J-T) effect. An external magnetic field results in further Zeeman splitting of the same egband. The ferromagnetism is assumed to originate from the exchange interaction between the spins of the localized core t2gelectrons. The J-T split itinerant (eg) bands are assumed to hybridize rather strongly with the on-site localized (t2g) levels. In the model under consideration the magnetization (m) as well as the lattice strain (e) are expected to depend on the model parameters of the system: i.e. the position of the localized level (d) with respect to the Fermi level, the strength of hybridization (v), the magnetic exchange coupling constant (g1), J-T coupling constant (g), external magnetic field (b) and the impurity concentration (x). The equations for the magnetization and the lattice distortion are solved self-consistently. The effect of different interactions on the quasiparticle bands and the density of states (DOS) are analyzed in detail to understand the evolution of the physical properties of the system on switching the interactions. The temperature dependence of the magnetization due to the localized electrons and that induced in the conduction band are studied.

scholarly journals Striping of orbital-order with charge-disorder in optimally doped manganites

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wei-Tin Chen ◽  
Chin-Wei Wang ◽  
Ching-Chia Cheng ◽  
Yu-Chun Chuang ◽  
Arkadiy Simonov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Doping Level ◽  
Colossal Magnetoresistance ◽  
Phase Segregation ◽  
Crystallographic Analysis ◽  
Prototype System ◽  
Jahn Teller ◽  
Doped Manganites ◽  
Natural Mechanism ◽  
Lattice Modes

AbstractThe phase diagrams of LaMnO3 perovskites have been intensely studied due to the colossal magnetoresistance (CMR) exhibited by compositions around the $${\frac{3}{8}}^{th}$$ 3 8 t h doping level. However, phase segregation between ferromagnetic (FM) metallic and antiferromagnetic (AFM) insulating states, which itself is believed to be responsible for the colossal change in resistance under applied magnetic field, has prevented an atomistic-level understanding of the orbital ordered (OO) state at this doping level. Here, through the detailed crystallographic analysis of the phase diagram of a prototype system (AMn$${}_{3}^{A^{\prime} }$$ 3 A ′ Mn$${}_{4}^{B}$$ 4 B O12), we show that the superposition of two distinct lattice modes gives rise to a striping of OO Jahn-Teller active Mn3+ and charge disordered (CD) Mn3.5+ layers in a 1:3 ratio. This superposition only gives a cancellation of the Jahn-Teller-like displacements at the critical doping level. This striping of CD Mn3.5+ with Mn3+ provides a natural mechanism though which long range OO can melt, giving way to a conducting state.

scholarly journals Colossal magnetoresistance and anomalous Hall effect in nonmagnetic semiconductors

2018 ◽  
Vol 185 ◽  
pp. 06011
Author(s):  
Sergei Obukhov ◽  
Tatiana Panysheva
Keyword(s):  
Magnetic Field ◽  
Colossal Magnetoresistance ◽  
Anomalous Hall Effect ◽  
Uniaxial Stress ◽  
Charge Carriers ◽  
Teller Distortion ◽  
Excitonic Insulator ◽  
Jahn Teller ◽  
Magnetic Ions ◽  
Jahn Teller Distortion

Colossal Magnetoresistance (CMR) in nonmagnetic semiconductors and magnetic materials has been investigated as a function of magnetic field, charge carriers concentration and temperature. Both types of materials demonstrated qualitative and quantitative coincidence of CMR dependence on magnetic field, charge carriers concentration and temperature. The findings support the CMR interpretation in the framework of the Excitonic Insulator (EI) model and transition of an insulating EI phase to conducting state under magnetic field for all types of materials under study. It is suggested that Jahn-Teller distortion caused by magnetic ions and external uniaxial stress could initiate EI phase formation

scholarly journals Описание колоссального магнитосопротивления La-=SUB=-1.2-=/SUB=-Sr-=SUB=-1.8-=/SUB=-Mn-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- на основе "спин-поляронного" и "ориентационного" механизмов проводимости в парамагнитной области температур

2020 ◽  
Vol 62 (5) ◽  
pp. 669
Author(s):  
С.А. Гудин ◽  
Н.И. Солин
Keyword(s):  
Magnetic Field ◽  
Colossal Magnetoresistance ◽  
Main Role ◽  
Spin Polaron ◽  
Temperature Range ◽  
Conduction Mechanisms ◽  
Theoretical Investigations ◽  
Temperature Dependences ◽  
The Magnetic Field ◽  
Good Agreement

Experimental and theoretical investigations of the resistance of the La1.2Sr1.8Mn2O7 single crystal in magnetic fields from 0 to 90 kOe and in the temperature range from 75 to 300 K has been studied. The magnetoresistance is determined by the “spin-polaron” and “orientation” conduction mechanisms. Using the method of separating contributions to the magnetoresistance from several conduction mechanisms, the observed magnetoresistance of La1.2Sr1.8Mn2O7 manganite in the temperature range of 75-300 K is described, good agreement between the calculated and experimental data is obtained. In a magnetic field of 0 and 90 kOe, the temperature dependences of the size of the spin polaron (in relative units) are calculated for the temperature range 75–300 K. It is shown, that the КМС value is determined by an increase in the linear size of the spin polaron (along the magnetic field), i.e. the main role in the magnitude of the colossal magnetoresistance is made by the change in the size of the magnetic inhomogeneities of the crystal.

scholarly journals Probing Phase Separation and Local Lattice Distortions in Cuprates by Raman Spectroscopy

2019 ◽  
Vol 4 (4) ◽  
pp. 87
Author(s):  
Liarokapis
Keyword(s):  
Raman Spectroscopy ◽  
Phase Separation ◽  
High Temperature ◽  
Colossal Magnetoresistance ◽  
High Temperature Superconductors ◽  
Relaxor Ferroelectrics ◽  
Order Parameters ◽  
Characteristic Family ◽  
Local Lattice ◽  
Lattice Distortions

It is generally accepted that high temperature superconductors emerge when extra carriers are introduced in the parent state, which looks like a Mott insulator. Competition of the order parameters drives the system into a poorly defined pseudogap state before acquiring the normal Fermi liquid behavior with further doping. Within the low doping level, the system has the tendency for mesoscopic phase separation, which seems to be a general characteristic in all high Tc compounds, but also in the materials of colossal magnetoresistance or the relaxor ferroelectrics. In all these systems, metastable phases can be created by tuning physical variables, such as doping or pressure, and the competing order parameters can drive the compound to various states. Structural instabilities are expected at critical points and Raman spectroscopy is ideal for detecting them, since it is a very sensitive technique for detecting small lattice modifications and instabilities. In this article, phase separation and lattice distortions are examined on the most characteristic family of high temperature superconductors, the cuprates. The effect of doping or atomic substitutions on cuprates is examined concerning the induced phase separation and hydrostatic pressure for activating small local lattice distortions at the edge of lattice instability.

Resonance Raman spectroscopy of the B1u region of benzene: Analysis in terms of pseudo‐Jahn–Teller distortion

1992 ◽  
Vol 96 (4) ◽  
pp. 2617-2628 ◽  
Author(s):  
Roseanne J. Sension ◽  
Richard J. Brudzynski ◽  
Shijian Li ◽  
Bruce S. Hudson ◽  
Francesco Zerbetto ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Jahn Teller Distortion

scholarly journals Magnetic Field Measurements during Magnetic Pulse Welding Using CMR-B-Scalar Sensors

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5925
Author(s):  
Voitech Stankevic ◽  
Joern Lueg-Althoff ◽  
Marlon Hahn ◽  
A. Erman Tekkaya ◽  
Nerija Zurauskiene ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Colossal Magnetoresistance ◽  
Welding Process ◽  
Nondestructive Method ◽  
Magnetic Field Measurement ◽  
Magnetic Pulse ◽  
Magnetic Pulse Welding ◽  
Pulse Welding ◽  
The Magnetic Field

The possibility of applying CMR-B-scalar sensors made from thin manganite films exhibiting the colossal magnetoresistance effect as a fast-nondestructive method for the evaluation of the quality of the magnetic pulse welding (MPW) process is investigated in this paper. This method based on magnetic field magnitude measurements in the vicinity of the tools and joining parts was tested during the electromagnetic compression and MPW of an aluminum flyer tube with a steel parent. The testing setup used for the investigation allowed the simultaneous measurement of the flyer displacement, its velocity, and the magnitude of the magnetic field close to the flyer. The experimental results and simulations showed that, during the welding of the aluminum tube with the steel parent, the maximum magnetic field in the gap between the field shaper and the flyer is achieved much earlier than the maximum of the current pulse of the coil and that the first half-wave pulse of the magnetic field has two peaks. It was also found that the time instant of the minimum between these peaks depends on the charging energy of the capacitors and is associated with the collision of the flyer with the parent. Together with the first peak maximum and its time-position, this characteristic could be an indication of the welding quality. These results were confirmed by simultaneous measurements of the flyer displacement and velocity, as well as a numerical simulation of the magnetic field dynamics. The relationship between the peculiarities of the magnetic field pulse and the quality of the welding process is discussed. It was demonstrated that the proposed method of magnetic field measurement during magnetic pulse welding in combination with subsequent peel testing could be used as a nondestructive method for the monitoring of the quality of the welding process.

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