First-to-second-order magnetic-phase transformation in La0.7Ca0.3-xBaxMnO3 exhibiting large magnetocaloric effect

In this study, high-density La1-xSrxMnO3:Ag0.2 (x = 0.1, 0.125, 0.15, 0.175, and 0.2) ceramics were prepared by the conventional sol-gel method. The peak values of temperature coefficient of resistivity (TCR) in all La1-xSrxMnO3:Ag0.2 samples were systematically controlled by changing the Sr content. A significant improvement in peak TCR have been observed through adjusting the Sr content. At doping molar ratio of x = 0.15 in La1-xSrxMnO3:Ag0.2 ceramics, the peak TCR value reached 14.7% K−1, and peak TCR temperature (TK, 288.2 K) was estimated to room-temperature (290 K). Visibly, it is encouraging to get such a high room-temperature TCR value. These findings suggested that La0.85Sr0.15MnO3:Ag0.2 ceramics could be used to prepare room-temperature uncooled infrared bolometers.

La1-xSrxMnO3:Ag0.2 (0.1 ≤ x ≤ 0.2) ceramics with large room-temperature TCR for uncooled infrared bolometers

We prepared a polycrystalline sample of orthorhombic La0.7Ca0.2Sr0.1MnO3 and then investigated its magnetic properties. Detailed studies and analyses in the vicinity of the ferromagnetic (FM)-paramagnetic phase-transition temperature prove the sample undergoing a second-order phase transition, where variations of the saturation magnetization and the initial susceptibility versus temperature obey asymptotic relations. Basing on the modified Arrott plot, we have determined the critical parameters (TC, β, γ, and δ) in the two characteristic regions of low- and high-magnetic fields, and in the cases of no-subtracting and subtracting the demagnetization field (Hd). The experimental results reveal that values of the critical parameters depend remarkably on analysis routes of isothermal-magnetization data. Intrinsically, β keeps close to the value expected for the 3D Heisenberg ferromagnets with ferromagnetic short-range interactions, while γ is close to the value of the mean-field theory. These results are diff...

Critical behavior and magnetic-entropy change of orthorhombic La0.7Ca0.2Sr0.1MnO3

Structure, magnetic and transport properties of La0.7Ca0.3-xSrxMnO3 thin films by sol-gel method

Critical behavior of La0.7Ca0.3Mn1−xNixO3 manganites exhibiting the crossover of first- and second-order phase transitions

A systematic investigation of the structural, magnetic and electrical properties of a series of nanocrystalline La 0.7 Sr x Ca 0.3− x MnO 3 materials, prepared by high energy ball milling method and then annealed at 900 °C has been undertaken. The analysis of the XRD data using the Win-metric software shows an increase in the unit cell volume with increasing Sr ion concentration. The La 0.7 Sr x Ca 0.3− x MnO 3 compounds undergo a structural orthorhombic-to-monoclinic transition at x =0.15. Electric and magnetic measurements show that both the Curie temperature and the insulator-to-metal transition temperature increase from 259 K and 253 K correspondingly for La 0.7 Ca 0.3 MnO 3 ( x =0) to 353 K and 282 K, respectively, for La 0.7 Sr 0.3 MnO 3 ( x =0.3). It is argued that the larger radius of Sr 2+ ion than that of Ca 2+ is the reason to strengthen the double-exchange interaction and to give rise to the observed increase of transition temperatures. Using the phenomenological equation for conductivity under a percolation approach, which depends on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the resistivity versus temperature data measured in the range of 50–320 K and found that the activation barrier decreased with the raising Sr 2+ ion concentration.

Structural, magnetic and magnetotransport behavior of La0.7SrxCa0.3−xMnO3 compounds

Magnetic and transport behaviors of Co substitution in La0.7Sr0.3MnO3 perovskite

Dependence of specific absorption rate on concentration of Fe3O4 nanoparticles: from the prediction of Monte Carlo simulations to experimental results

This work investigates the structure, optical and electrical conductivity properties of BaTi1−xCoxO3 (0≤ x ≤0.1) ceramics prepared by the hydrothermal method. The X-ray diffraction and Raman scattering analysis demonstrates that the prepared samples have a single-phase tetragonal structure with P4mm symmetry. The UV-vis diffuse reflectance spectrum confirms the influence of Co concentration on the direct optical band gap of BaTi1−xCoxO3 ceramics. The optical band gap shifts from 3.14 eV to 3.44 eV as the Co concentration increases from 0 to 0.1. The dielectric constant increases with the depletion of frequency according to the Maxwell–Wagner and Koops model. The AC conductivity versus frequency curve indicates that the conduction mechanism is determined by using the correlated barrier hopping (CBH) model. The Cole–Cole plot of the complex impedance was investigated for the prepared samples. The compounds showed dielectric relaxation of the non-Debye type.

/pdf/structural-optical-and-conductivity-properties-in-tetragonal-3b77mxch.pdf

L.H. Nguyen

Papers

Structural, magnetic and magnetotransport behavior of La0.7SrxCa0.3−xMnO3 compounds

Magnetic and transport behaviors of Co substitution in La0.7Sr0.3MnO3 perovskite

Dependence of specific absorption rate on concentration of Fe3O4 nanoparticles: from the prediction of Monte Carlo simulations to experimental results

Structural, optical and conductivity properties in tetragonal BaTi1−xCoxO3 (0≤ x ≤0.1)

Facile development of carbon quantum dot deposited titanate-based materials for environmental application