Manganite System Research Articles

The production system and structural characterization of CAMNi-xTIxO3 with x values ranging from 0.0 to 1.0 are investigated

In this work, we report the production of new composite perovskite manganite system CaMn ,Ti,O, with doping x = 0.25, 0.5 and 0.75, reaction sintering method solid state. Structural characterization was performed using the technique of X-ray Diffraction (XRD) and the Rietveld method, obtaining a tetragonal structure, with Prima spatial group (# 62) (a=5.3586a y a=5.2997A: b=7.5041 A y b=7.5526a; c+5.3l82& y c=5.3278A). In this paper takes the discussion on possible structural changes with changes in the system titanium CaMn, ,Ti,O,.

A study on the kinetic arrest of magnetic phases in nanostructured Nd0.6Sr0.4MnO3 thin films

The Nd0.6Sr0.4MnO3 (NSMO) manganite system exhibits a phase transition from paramagnetic insulating (PMI) to ferromagnetic metallic (FMM) state around its Curie temperature T C = 270 K (bulk). The morphology-driven changes in the kinetically arrested magnetic phases in NSMO thin films with granular and crossed-nano-rod-type morphology are studied. The manganite thin films at low temperatures possess a magnetic glassy state arising from the coexistence of the high-temperature PMI and the low-temperature FMM phases. The extent of kinetic arrest and its relaxation was studied using the ‘cooling and heating in unequal field (CHUF)’ protocol in magnetic and magnetotransport investigations. The sample with rod morphology showed a large extent of phase coexistence compared to the granular sample. Further, with a field-cooling protocol, time-evolution studies were carried out to understand the relaxation of arrested magnetic phases across these morphologically distinct thin films. The results on the devitrification of the arrested magnetic state are interpreted from the point of view of homogeneous and heterogeneous nucleation of the ferromagnetic phase in the paramagnetic matrix with respect to temperature.

Magnetocaloric effect in PrGd1-xBaxMn2O6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system

Magnetocaloric effect in PrGd1-xBaxMn2O6 (0.0 ≤ x ≤ 1.0) double perovskite manganite system

The symmetry aspect of magnetocaloric effect in LaxBi0.3-xCa0.7MnO3 manganites

Manganites exhibit many novel properties, such as giant magnetoresistance and a large magnetocaloric effect (MCE). In this work, we report the magnetic properties and magnetocaloric effects of polycrystalline Bi0.3-xLaxCa0.7MnO3 (x = 0, 0.1, 0.2) ceramics from perspective of symmetry, where Raman active modes and corresponding phonons are used as probes to detect charge disorder and local structure distortion. Further, the large MCE is elucidated by the La doping induced Jahn-Teller distortion and valence perturbations. The orthorhombic and rhombohedral structural transition in doping manganites has shown a link between the complex magnetic phase transition and magnetic entropy. We attribute these intriguing behaviors to the temperature-dependent competition between the orbital order and charge order. Our results provide an approach to improve the MCE of manganite systems for future magnetic refrigeration applications.

Tuning Colossal Magnetoresistance Effect Through Chemical Substitution In Perovskite Manganites

Objective: This research is focused on the colossal magnetoresistance (CMR) effect tunability via chemical substitution in perovskite manganites. The objective is to learn how changing the chemical structure of these compounds affect their magnetic and electronic characteristics particularly the CMR effect. Methods: Perovskite manganite materials were prepared by the chemical substitution method to tune the composition of transition metal ions and rare-earth elements. The structural, magnetic, and electronic characterizations were done by the means of X-ray diffraction, magnetization measurements, and electrical transport measurements. Results: The study showed that the selective chemical substitution within the perovskite structure could be used to modulate the CMR effect in manganite materials. Due to the differences in chemical structure the magnetic ordering, charge carrier concentration and electronic band structure are altered which in turn influence the magnitude of the CMR effect. For example, specific chemical substitutions were shown to remarkably strengthen the CMR effect, leading to better magnetoresistance characteristics. Conclusion: This study demonstrates the possibility of tuning the CMR effect by the chemical substitution of Mn perovskite materials. By manipulating the chemical composition, it is achievable to fine-tune the magnetic and electronic characteristics for various spintronics, magnetic sensors and other devices that need high magnetoresistance effects. The results help to gain more knowledge about CMR in manganite systems and provide the guidance for the research on improving their performance.

Investigation of magnetic properties and colossal magnetoresistance in nanocrystalline doped manganite

Here in, we report structural, magnetic, and magneto-transport properties of nanocrystalline La0.6Ag0.2Bi0.2MnO3 prepared using citrate sol–gel method. By using scanning and transmission electron microscopy measurements, the morphology and particle size of the sample have been confirmed. The Mn2p x-ray photoelectron spectroscopy spectra revealed the nanoparticles contained the coexistence of Mn3+ and Mn4+ ions with Mn3+/Mn4+ ratio of 2:1. Field-cooled and zero field-cooled magnetization protocols with temperature span of 5 K–300 K, confirm the paramagnetic (PM) to ferromagnetic (FM) phase transition at critical temperature, ∼ 146 K. The complete investigation of isothermal magnetization (), Arrott plots, and magnetocaloric effect as well as quantitative analysis of second-order phase transition has been studied. The criticality at the PM-FM transition was examined for the sample, and the obtained critical exponents were verified for their reliability through the utilization of the scaling hypothesis and Kouvel-Fisher plot. We observed a large magnetic entropy change (∼7 J-Kg−1K−1) at upon 5 T magnetic field strength. The renormalized magnetic entropy change plots are found to collapse onto a single curve, thus verifying the universality of the sample. Above the metal–insulator transitions the electrical resistivity shows a small polaron hopping conduction mechanism, however, at low temperatures scattering mechanism dominates and the whole range was explained by the universal percolation model. The colossal value of negative MR is found to be 88% at 168 K under an applied field strength of 2 T. As a result of our experimental data, we can grasp the intuitive understanding of magnetic as well as transport properties in Bi-doped manganite systems potential for magnetic sensors and spintronics applications.

Ultrafast activation of the double-exchange interaction in antiferromagnetic manganites

In doped manganite systems, strong electronic correlations result in rich phase diagrams where electron delocalization strongly affects the magnetic order. Here, we employ a femtosecond all-optical pump-probe scheme to impulsively photodope the antiferromagnetic parent manganite system CaMnO3 and unveil the formation dynamics of a long-range ferromagnetic state. We resonantly target intense charge transfer electronic transitions in CaMnO3 to photodope the system and probe the subsequent dynamics of both charges and spins using a unique combination of time-resolved terahertz spectroscopy and time-resolved magneto-optical Faraday measurements. We demonstrate that photodoping promotes a long-lived population of delocalized electrons and induces a net magnetization, effectively promoting ferromagnetism resulting from light-induced carrier-mediated short-range double-exchange interactions. The picosecond set time of the magnetization, much longer than the electron timescale, and the presence of an excitation threshold are consistent with the formation of ferromagnetic patches in an antiferromagnetic background.

Strain fields and critical phenomena in manganites I: spin-lattice Hamiltonians

We use a model Hamiltonian to study critical phenomena in manganites. This Hamiltonian includes long-range strain interactions, and a coupling between the magnetic order parameter and the strain field. We perform a perturbative renormalization group (RG) analysis and calculate the static critical exponents, correct to the one-loop level. We compare our RG results with many experiments on doped manganite critical systems. Our theory is in excellent agreement with the experimental values for the critical exponents.

Structural, conductivity, and complex impedance properties of the La0.7Ag0.3Mn1−xZnxO3 (x = 0 and x = 0.025) samples

In this paper, the structural and dielectric properties of La0.7Ag0.3Mn1−xZnxO3 (x = 0 and 0.025) manganite system are investigated. The x-ray diffraction analysis confirms that all compounds crystallized in the rhombohedral structure with R3̄C space group. The effects of Zn substitution on the crystal structure and the dielectric properties were studied by using the impedance spectroscopy technique at room temperature and over a wide range of frequencies. Electrical conductance curves are found to obey the Jonscher universal power law. We note a decrease in the conductivity when increasing the Zn content from x = 0 to x = 0.025. This behavior can be associated with the introduction of a very low concentration of a non-magnetic Zn ion, which distorts the octahedral MnO6 neighbor. The analysis of the complex impedance spectra reveals a single semicircular arc reflecting a non-Debye-type relaxation process. We conclude from the best fits that the equivalent circuit formed in our case is defined as a grain resistance Rg in series with a parallel combination of grain boundary resistance Rgb and constant phase element impedance (ZCPE).

In-situ investigation on the oxygen vacancy-driven topotactic phase transition in charge-orbital ordered Nd0.5Sr0.5MnO3 films

The topotactic phase transition from perovskite to oxygen vacancies ordered brownmillerite structure in transition metal oxides intrigues various new application possibilities. However, the in-situ observation of the oxygen vacancies formation process accompanying the phase transition is still rare. Here in this article, we report the topotactic phase transition from the perovskite to a brownmillerite phase transition in the intermediate bandwidth- (101)-Nd0.5Sr0.5MnO3-δ films. The oxygen vacancies migration process in the films was identified by the TEM technique during the in-situ high vacuum annealing process. The TEM results demonstrate a vertical brownmillerite structure with the oxygen vacancies channel perpendicular to the film plane in the (101)-oriented films. Moreover, the in-situ investigation reveals that oxygen atoms in the {010}PV plane of the perovskite phase migrate out of the film along the out-of-plane <101>PV direction at first, and the formed oxygen vacancies become ordered by elongating the high-vacuum annealing process to 42 h, transforming to the brownmillerite structure. Further studies reveal that the associated physical properties of the topotactic phases can be controlled by the phase transition. The charge-orbital ordered antiferromagnetic insulating ground state transfers to a highly insulating state with a novel magnetic phase that is distinct from that of brownmillerite structure of other manganites. The present studies thus pioneered topotactic phase transition in a new manganite system and provide useful information for developing perovskite-based functional materials by defect engineering.

Baroentropy change estimation using modified Maxwell equation through magnetization and resistivity measurements under pressure: An indirect method of barocaloric effect

We investigate the baroentropy change on manganites (Δ S b M and Δ S b M- ρ ) using modified form of Maxwell’s equation through magnetization and magnetization-resistivity measurements. Hence, we choose two Mn-site doped pervoskite manganites Pr 0.6 Ca 0.4 Mn 0.96 Co 0.04 O 3 and Pr 0.6 Ca 0.4 Mn 0.96 Cr 0.04 O 3 due to strong correlation between magnetic and electrical properties. The two external perturbations such as magnetic field and hydrostatic pressure have a similar influence on magnetic and transport properties of manganite systems due to its strong coupling between spin, charge, and orbital degrees of freedom. Baroentropy change, similar to magneto entropy change, could be estimated by replacing magnetic field in Maxwell’s equation by pressure in perovskite manganites. The estimated values of Δ S b M and Δ S b M-ρ using proposed equations well agree with each other, justifying the use of these equations. As these values are deduced from pressure dependent magnetization and resistivity measurements, this method of baroentropy change estimation is very useful as well as reliable in order to select application-oriented systems from the manganites family. • H and P have a similar influence on magnetic and transport properties of manganites. • Two modified forms of Maxwell’s equation are proposed to estimate baroentropy changes. • ΔS b M and ΔS b M-ρ values completely rely on magnetization and resistivity of a system. • P and H increase the baroentropy change of selected Co and Cr doped systems. • These are reliable for manganites in which analogue in magnetic and transport properties.

Investigation of the effect of sintering temperature on structural, magnetic and magnetocaloric properties in PrCaMn2O6 double perovskite manganite system

Investigation of the effect of sintering temperature on structural, magnetic and magnetocaloric properties in PrCaMn2O6 double perovskite manganite system

Structural and Transport Properties of La&lt;sub&gt;0.85&lt;/sub&gt;Te&lt;sub&gt;0.15&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt; Manganite and its Composite with Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

The manganite systems investigated during the present work are pure La0.85Te0.15MnO3 (LTMO) and its composite with 12% concentration of Al2O3 nano powder (LTMO + Al2O3). The materials were prepared by the modified auto combustion technique. The samples were characterized by X-ray diffraction. The powder X-ray diffraction pattern of pure LTMO at room temperature shows that sample is in single phase with no detectable secondary phases and the sample have a rhombohedral structure in hexagonal with the space group R3c. The XRD pattern of LTMO + 12% Al2O3 indicates the clear presence of Al2O3 nano phase in the composite. In the present study, the FTIR Spectroscopy of both samples was carried out. It is clear from the Vibrational assignment for the value of corresponding peak position of FTIR spectra that no extra unwanted impurity is present in samples. A quantitative analysis of the energy dispersive spectroscopy (EDS) data indicates that the observed concentration of elements are very close to the calculated values from its chemical formula. R-T measurements reveals that the addition of secondary phase in manganite strongly influenced on electronic and magnetoresistance behaviour. We summarise some of the salient features of the results.

Quenched Disorder–Controlled Resistive Relaxation in Near-Half-Doped Manganite Systems

Quenched Disorder–Controlled Resistive Relaxation in Near-Half-Doped Manganite Systems

Extended “orbital molecules” and magnetic phase separation in Bi0.68Ca0.32MnO3

The low-temperature structure of ${\mathrm{Bi}}_{0.68}{\mathrm{Ca}}_{0.32}{\mathrm{MnO}}_{3}$ has been solved from electron and neutron diffraction data. The quantitative simultaneous refinement indicates an ordering of the Mn cations in a ``stripe/chess''-like pattern. The ordering is accompanied by the formation of short Mn---Mn distances and the rearrangement of the Mn---O bonds indicating the development of complex extended ``orbital molecules.'' The primary order parameter breaks inversion symmetry and allows the generation of a spontaneous electrical polarization as the secondary order parameter. The neutron data at low temperature indicate the coexistence of a pseudo-CE long-range-ordered structure with a strongly reduced moment and short-range ferromagnetic correlations. These results indicate an intricate competition between the charge, orbital, and magnetic degrees of freedom and the ${\mathrm{Bi}}^{3+}$ stereoactivity in this manganite system.

Structural and magneto-transport features of cobalt-substituted mixed-valence manganites

We report the results of a detailed investigation of the role of cation substitution Co → Mn on the structural, microstructural, magnetic, and transport properties of the manganite system La2/3Ca1/3Mn1−xCoxO3 (x = 0.0, 0.1, 0.2 and 0.3). It is found that the replacement of Mn with Co does not change the crystal structure of the parent compound La2/3Ca1/3MnO3 which crystallizes in orthorhombic structure with Pbnm space group. From a systematic analysis of the magneto-transport measurements, it has been shown that the cobalt substitution leads to a decrease in the system magnetization and lowering of Curie and metal–insulator transition temperatures. The magnetoresistance percentage (MR%), which is found to change significantly by Co substitution and exceeds 100% for x = 0.3 sample at low temperatures, is also reported at 1 T applied magnetic field.

Exotic Long-Range Surface Reconstruction on La0.7Sr0.3MnO3 Thin Films.

Due to an extremely diverse phase space, La1-xSrxMnO3, as with other manganites, offers a wide range of tunability and applications including colossal magnetoresistance and use as spin-polarized electrodes. Here, we study an unprecedented, exotic surface reconstruction (6 × 6) in La1-xSrxMnO3 (x = 0.3) observed via low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) shows the surface is relatively flat, with unit-cell step heights, and X-ray photoelectron spectroscopy (XPS) reveals a strong degree of Sr segregation at the surface. By combining electron diffraction and first-principles computations, we propose that the long-range surface reconstruction consists of a Sr-segregated surface with La (6 × 6) ordering. This study expands our understanding of manganite systems and underscores their ability to form interesting surface reconstructions, driven largely by cation segregation that can potentially be controlled for tuning surface ordering.

Structure analysis of electromagnetic waves absorbing material a lanthanum manganite system of (La0.8Ba0.2)(Mn(1-x)/2ZnxFe(1-x)/2)O3

Solid compound of lanthanum manganite system of (La0.8Ba0.2)(Mn(1-x)/2ZnxFe(1-x)/2)O3 has been synthesized via conventional solid state reaction route using lanthanum oxide (La2O3), barium carbonate (BaCO3), zinc oxide (ZnO), ferric oxide (Fe2O3) and manganese carbonate (MnCO3) powders as it raw materials. High energy ball milling was used to mix the material for 5 hours. It is then sintered at 1000°C for 5 hours. X-ray powder diffraction method (XRD) and scanning electron microscopy (SEM) was used to analyze the change of structure of the solid compound. The refinement pattern result of the XRD shown that a single phase was occurred in the form of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3. It has trigonal lattice crystal structure of (r-3c) point group with lattice parameter of a = b = 5.515 Å and c = 13.551 Å, α = β = 90° and γ = 120°, a volume unit cell of V = 356.904 Å3 and a density of ρ = 6.745 g.cm−3. The SEM result shown that the surface morphology of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3 has a homogeneous sphere structure. The XRD and SEM structure analysis result of the lanthanum manganite system of (La0.8Ba0.2)(Mn0.4Zn0.2Fe0.4)O3 shown that the compound is feasible for further studied.

Strain-Dependent Resistivity of Granular Manganite Systems: A Simple Quantitative Approach

The effects of an applied strain tensor on the electrical resistivity of a manganite granular system are investigated using a simple approach describing the induced deformation in terms of the tilt angle between adjacent grains. The results obtained assuming the resistivity of each grain as given by a metallic part, coming from the inner grain, and a surface-related tunnel contribution, allow us to estimate appreciable resistivity variations even in the case of small deformation angles.

Usefulness of theoretical approaches and experiential conductivity measurements for understanding manganite-transport mechanisms

Experimental measurements and numerous theoretical models have been employed to comprehend the dynamics of charge carriers in manganite system. The present work highlights the electrical transport of La0.5Ca0.4Ag0.1MnO3 compound in the temperature range [80 K–700 K]. It is found that the conductivity spectra of the studied sample present a double Jonscher variation, universal Jonscher evolution and Drude variation respectively for low, intermediate and high temperature ranges. The temperature dependence of the frequency exponent confirms the efficiency of the quantum mechanical tunneling, the non-overlapping small polaron tunneling and the correlated barrier hopping mechanisms at separated dispersive regions. DC conductivity analysis confirms the semiconductor behavior of the studied sample. Then, the transport properties have been explained in term of a thermally activated small polaron hopping and Mott-variable range hopping processes respectively at high and low temperature sides. Also, the disorder energy is predicted to decrease with rising frequency which could be due to variation in the separation path between the hop centers. Moreover, Greaves variable range hopping model is the suitable one that describes the transport properties in the intermediate temperature range. The scaling approach indicates that the time temperature superposition principle is valid in the temperature side [180 K–360 K].