Magnetic and Cytotoxicity Properties of La1−x Sr x MnO3 (0 ≤ x ≤ 0.5) Nanoparticles Prepared by a Simple Thermal Hydro-Decomposition

This study reports the magnetic and cytotoxicity properties of magnetic nanoparticles of La_1−x Sr _x MnO₃ (LSMO) with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 by a simple thermal decomposition method by using acetate salts of La, Sr, and Mn as starting materials in aqueous solution. To obtain the LSMO nanoparticles, thermal decomposition of the precursor was carried out at the temperatures of 600, 700, 800, and 900 °C for 6 h. The synthesized LSMO nanoparticles were characterized by XRD, FT-IR, TEM, and SEM. Structural characterization shows that the prepared particles consist of two phases of LaMnO₃ (LMO) and LSMO with crystallite sizes ranging from 20 nm to 87 nm. All the prepared samples have a perovskite structure with transformation from cubic to rhombohedral at thermal decomposition temperature higher than 900 °C in LSMO samples of x ≤ 0.3. Basic magnetic characteristics such as saturated magnetization (M _S) and coercive field (H _C) were evaluated by vibrating sample magnetometry at room temperature (20 °C). The samples show paramagnetic behavior for all the samples with x = 0 or LMO, and a superparamagnetic behavior for the other samples having M _S values of ~20–47 emu/g and the H _C values of ~10–40 Oe, depending on the crystallite size and thermal decomposition temperature. Cytotoxicity of the synthesized LSMO nanoparticles was also evaluated with NIH 3T3 cells and the result shows that the synthesized nanoparticles were not toxic to the cells as determined from cell viability in response to the liquid extract of LSMO nanoparticles.     

Hysteresis and vertical anisotropy of magnetoresistance in La0.67A0.33MnOz (A=Ca,Sr) polycrystalline films deposited on amorphous quartz substrates

Polycrystalline La_0.67A_0.33MnO_z (A=Ca, Sr) thin films with [202] preferred orientation were synthesized on amorphous quartz substrates by means of metal organic deposition (MOD) technology. The Curie temperature (T_C) and metal?insulator transition temperature (T_p) are 172 K, 247 K and 227 K, 335 K for La_0.67Ca_0.33MnO_z (LCMO) film and La_0.67Sr_0.33MnO_z (LSMO) film, respectively. The hysteresis and vertical anisotropy behaviors of MR are exhibited by the films below T_C, which strongly relies on the magnetization process. The magnitude of these magnetotransport properties would decline with increasing temperature. The in-plane hysteric MR behaviors could be explained by multiple-domain model. For vertical anisotropy of MR, demagnetization effect plays an important role. Especially, compared to LCMO film, LSMO film still presents the above hysteretic MR effect and vertical anisotropic MR at RT due to its higher T_C.     

Structural,ferroelectric, magnetic and magnetoelectric properties of (1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 -x La0.67Sr0.33MnO3 lead-free magnetoelectric composites

The influence of an additional La_0.67Sr_0.33MnO₃ (LSMO) magnetic phase on the structural, ferromagnetic, ferroelectric, and magnetoelectric properties of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) ferroelectric phase was studied for composites of (1-x)BCZT -xLSMO (x = 0, 25, 50, 75 and 100%). The ferroelectric BCZT sample showed a perovskite single phase formation with a tetragonal crystal structure of the P4mm space group, and the magnetic phase of LSMO presented a rhombohedral crystal structure of R3c space group as shown by XRD. The composite sample with 25% LSMO exhibited large ferroelectric and piezoelectric properties with remnant, saturation polarization, and coercive electric field P_r ~7.74 μC/cm², P_s ~11.69 μC/cm² and E_C ~12.22 kV/cm with a piezoelectric coefficient d₃₃ ~ 231 pC/N. The magnetic characterization for the composites showed that the sample containing 75% of LSMO revealed the highest remnant, saturation magnetization, and coercive field of M_r ~1.358 emu/g, M_s ~19.17 emu/g, and H_C ~33.19 Oe, respectively. Moreover, it revealed the largest magnetoelectric coupling coefficient α_ME ~2.51 mV/cm.Oe with high coupling quality at a lower applied magnetic field. The results highlight the value of these composites as lead-free room temperature magnetoelectric sensors and actuators.     

Structural characterization and magnetic properties of single-crystalline (La0.6Pr0.4)0.67Ca0.33MnO3 nanowires

Herein, structural and magnetic properties of single-crystalline (La_0.6Pr_0.4)_0.67Ca_0.33MnO₃ nanowires synthesized via a hydrothermal process are reported. The nanowires are crystallized in an orthorhombic structure (Pnma space group). Their lattice parameters follow the relationship a ≈ c ≈ b/√2 These nanowires exhibited a clean and smooth surface with diameters of 60-120 nm and an average length of approximately 2.0 μm. High-resolution transmission electron microscopy images confirmed the single-crystalline nature of the nanowires growing along the [100] direction. The nanowires demonstrated magnetic hysteresis loops at low temperatures and a weak exchange bias (EB) effect. Paramagnetic (PM)–ferromagnetic (FM) phase transition occurred at a Curie temperature (T_C) of 224 K, and strong irreversibility between zero-field-cooled (ZFC) and field-cooled (FC) magnetization (M_ZFC and M_FC, respectively) curves was observed at 273 K. The M_ZFC curve exhibited a significantly broad peak with a maximum at a freezing temperature (T_f) of 134 K. Relative difference between M_FC and M_ZFC in the nanowires [(M_FC − M_ZFC)/M_FC] rapidly increased below T_f and reached approximately 50% below 35 K. The effective magnetic moment deduced from the Curie constant is larger than the theoretical value, indicating short-range FM interactions in the nanowires. A positive PM T_C (θ_p) implies dominant FM interactions in the nanowires, and θ_p > T_C observed herein indicates the existence of short-range ordered states above T_C.     

Influence of Ce addition on the structural,magnetic, and magnetocaloric properties in La0.7−xCexSr0.3MnO3 (0≤x≤0.3) ceramic compound

We report improvement in the magnetocaloric properties of Ce-doped lanthanum manganites. Polycrystalline La_0.7−xCe_xSr_0.30MnO₃ (0≤x≥0.3) samples were prepared using the conventional solid-state reaction method with phase purity and structure confirmed using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order ferromagnetic transition in parent sample and as well as in doped sample with Curie temperature decreasing progressively with increasing Ce-concentration from ~370 K for x=0.0 to 310 K for x=0.30. Magnetic entropy change (ΔS_M) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field dependent magnetization curves. A large ΔS_M associated with the ferromagnetic–paramagnetic transition in La_0.7−xCe_xSr_0.30MnO₃ samples has been observed. The value of ΔS_M was found to increase with Ce-doping up to x=0.15 and the highest value of 2.12 J kg⁻¹ K⁻¹ (at ΔH=2 T) was observed for La_0.55Ce_0.15Sr_0.30MnO₃ sample near the Curie temperature of 356 K. Also, improved relative cooling power of ~122 J kg⁻¹ was observed for the same sample. Due to the large magnetic entropy change and high Curie temperature, the La_0.55Ce_0.15Sr_0.30MnO₃ sample is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature.     

Effects of different high-pressure syntheses on the magnetization reversal properties of Bi2FeMnO6 ceramics

Bi₂FeMnO₆ ceramics were prepared under atmospheric pressure and a high pressure of 1–6 GPa. The effects of different high-pressure syntheses on the microstructures were analyzed by X-ray diffraction and Rietveld refinement, scanning electron microscopy–energy-dispersive spectroscopy, X-ray photoelectron spectrometer, and Raman spectroscopy test. The temperature dependence of magnetization was systematically investigated for all samples. There was a transition from rhombohedral R3c structure to orthorhombic phase Pnam with increasing synthetic pressure. The samples synthesized under atmospheric pressure are rhombohedral R3c with antiferromagnetic (AFM) magnetic temperature (M–T curves). The samples synthesized under a high pressure of 5–6 GPa are orthorhombic phase Pnam with the magnetization reversal effect, whereas the lower high-pressure (1–3 GPa) synthesized samples might be in the transitional area between them. This structural transformation is accompanied by the transformation from normal AFM M–T curves to a typical magnetization reversal effect. The relationship between the lattice distortion and the internal magnetic competition mechanism of the material was discussed. The existence of magnetization reversal in these systems may ascribe to the competition between the single-ion magnetic anisotropy and the Dzyaloshinsky–Moriya interaction.     

Simultaneous oxidation of aromatic compounds using Sr-doped lanthanum manganites as catalysts

Strontium-doped lanthanum manganites, La_1-xSr_xMnO₃ (LSMO), are promising and affordable catalysts for oxidative degradation of volatile organic compounds. LSMO catalysts (x = 0, .1, .2, and .3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The phase composition was confirmed by X-ray diffraction and Rietveld refinement analysis, while the oxygen content was determined by Mohr's salt permanganate titration. Morphology and porosity of prepared catalysts was correlated to catalytic oxidation of benzene, toluene, ethylbenzene and o-xylene. It was observed that both synthesis methods yielded catalysts of similar average pore size diameter and specific surface area, but the pore size distribution differed: CNA-prepared catalysts had a multimodal pore size distribution, while the coprecipitated ones had a single maximum at 4 nm. Catalysts prepared by the CNA method have shown a higher catalytic activity in the temperature range 373–723 K, as the presence of Mn³⁺/Mn⁴⁺ mixed valences increased their reducibility.     

Magnetic and electric properties of wrinkled manganite films derived by sol‐gel method

Flat and wrinkled La_0.7Sr_0.3MnO₃ (LSMO) thin films were prepared by sol‐gel method, respectively, on Si (001) substrates by adjusting heating rate at drying stage. Wrinkled film has larger grains than flat film. Coercive field (about 27 Oe) of wrinkled film is higher than that of flat film, which is much low as around 5 Oe. Compared with flat films, wrinkled films have larger magnetization, higher Curie temperature (334 K) and peak resistivity temperature (243 K), and lower resistivity (0.18 Ohm·cm at 300 K). The introducing of wrinkles is an efficient way to induce compressive stress in sol‐gel derived polycrystalline LSMO films and enhance the magnetic and electric properties.     

Investigation of Optimal Growth Conditions of La0.7Sr0.3MnO3–Bi2Sr2Ca1Cu2O8 Heterostructures

The deposition conditions of less explored La_0.7Sr_0.3MnO₃ (LSMO) and Bi₂Sr₂Ca₁Cu₂O₈ (Bi‐2212) heterostructures are investigated in terms of two different deposition orders. One is in the order of Bi‐2212/LSMO and the other is LSMO/Bi‐2212. The experimental results indicate the metal‐insulator transition (T_MI) and Curie temperature (T_Curie) of LSMO as well as the superconducting critical transition (T_C) of the Bi‐2212 to be very sensitive to the order of deposition. In Bi‐2212/LSMO, due to factors such as strain, roughness, and degree of oxygenation, superconductivity is not stabilized to interact with LSMO. Whereas the LSMO/Bi‐2212 order of deposition displays both superconductivity and ferromagnetic behavior for a single post annealing condition. In LSMO/Bi‐2212, depositing Bi‐2212 as a top layer and post annealing in air is crucial to achieve optimal carrier concentration for exhibiting high T_C.     

Physical Properties of La1−xEuxPO4,0 ≤ x ≤ 1, Monazite‐Type Ceramics

Synthetic La_1?xEu_xPO₄ monazite‐type ceramics with 0 ≤ x ≤ 1 have been characterized by ultrasound techniques, dilatometry, and micro‐calorimetry. The coefficients of thermal expansion and the elastic properties are, to a good approximation, linearly dependent on the europium concentration. Elastic stiffness coefficients range from 182(1) to 202(1) GPa for c₁₁ and from 53.8(7) to 61.1(4) GPa for c₄₄. They are strongly dependent on the density of the sample. The coefficient of thermal expansion at 673 K is 8.4(3)  × 10^?6 K^?1 for LaPO₄ and 9.9(3)  × 10^?6 K^?1 for EuPO₄, respectively. The heat capacities at ambient temperature are between 101.6(8) J·(mol·K)^?1 for LaPO₄ and 110.1(8) J·(mol·K)^?1 for EuPO₄. The difference between the heat capacity of LaPO₄ and the Eu‐containing solid solutions is dominated by electronic transitions of the 4f‐electrons at temperatures above 75 K.     

Robust temperature coefficient of resistance of polycrystalline La0.6Ca0.4MnO3 under magnetic fields at room temperature

In the presence of magnetic field, reducing the loss in temperature coefficient of resistance (TCR) and increasing metal−insulator transition point (T_MI) to room temperature are the most important concerns for the application of perovskite manganites in high−precision thermistors. Based on emerging evidence, relevant factor to address these problems lies in the interaction between Jahn−Teller (JT) distortion and magnetic field, which results in spin−orbital coupling (SOC) effect and significantly influences TCR and T_MI. In this work, we studied the magnetic field induced SOC effect in polycrystalline La_1−xCa_xMnO₃ (x = 0.225–0.45) materials synthesized via sol−gel technique. Compounds undergo the JT distortions with increasing Ca dopant content, and the most pronounced distortion of 0.0144 at x = 0.40 is correlated with a basal−plane distortion mode. All samples exhibit T_MI values between 262 K and 288 K, indicating the enhancement of doping−induced double−exchange interaction. In the magnetic field of 1 T, SOC effect sufficiently suppresses the deterioration of TCR caused by deficient magnetization in La_0.6Ca_0.4MnO₃ to a value of 2.9%·K⁻¹ at room temperature (287 K).     

Synthesis of La0.7Sr0.3MnO3 at 800 °C using citrate gel method

Manganite systems have been of considerable interest in the recent past due to their potential to operate in wide property range and also to serve as effective magnetic sensing and storing devices when synthesized using stringent conditions. We report a novel citrate gel method, in which La_0.7Sr_0.3MnO₃ system has been synthesized at temperature 800 °C (LSMO800) with the synthesis duration is 6 h. The results have been compared with the sample synthesized at 1050 °C (LSMO1050). The synthesized bulk polycrystalline sample shows single-phase nature with the increase in particle size from ∼50 nm to 300 nm with the increase in the sintering temperature. The magnetization data for LSMO800 shows well-defined hysteresis with saturation magnetization at around 1800 Oe and Curie temperature at 360 K, which is slightly lower than that of LSMO1050, which is 375 K. The results can be well attributed to the grain boundary effects.     

The magnetic,thermal transport properties,magnetothermal effect and critical behavior of Co3Sn2S2 single crystal

Through the magnetic/thermal transport measurements combined with the analyses of magnetocaloric effect and critical behavior of Co₃Sn₂S₂ single crystal, the main results we obtained are as follows: in the case of the magnetic field H//c-axis, Co₃Sn₂S₂ exhibits the phase-separation state below T_c in the low-field region (H < 500 Oe). T_c increases slightly from 174 to 177 K with an increase in H from 100 to 10 kOe. The second-order magnetic phase transition near T_c and the itinerant ferromagnetism below T_c are identified. The magnetization below T_c matches well with the three-dimensional Ising model, instead of the mean-field model. In the case of H//ab, T_c changes between 175 and 178 K with varying H. Noticeably, M above T_c exhibits a small positive value, instead of the null M as commonly expected in the paramagnetic region. An extra phase transition below 166 K is observed. The magnetic transition near T_c seems not to be the second-order phase transition. All results show a significant characteristic of anisotropic magnetic phase transition for the Co₃Sn₂S₂ single crystal. They support mutually those in previous reports, moreover, some new phenomena are also observed. They also provide the experimental evidences for the deep insight into the magnetic phase–transition behavior of Co₃Sn₂S₂.     

Structure and properties of (1-x)La0.67Sr0.33MnO3/xMnOδ multicomponent composite

(1-x)La_0.67Sr_0.33MnO₃/xMnO_δ [(1-x)LSMO/xMnO_δ] multicomponent composites were prepared. Their structure and properties were investigated as function of composition. X-ray diffraction and x-ray photoelectron spectroscopy confirmed the coexistence of MnO, Mn₂O₃ and MnO₂. It was found that MnO_δ introduction led to decreased average grain size and metal-insulator transition temperature. But it can increase maximum resistivity and magnetoresistance. The corresponding values were 2.0 μm, 370 K, 0.017 Ω cm, −24.7% (10 K, 2 T) for x = 0 and 0.7 μm, 225 K, 1.899 Ω cm and −25.6% (10 K, 2 T) for x = 0.3. However, the ferromagnetic Curie temperature was almost composition-independent with the value of 305 K. These results indicate that forming multicomponent composite by introducing ferromagnetic second phases can suppress the drawbacks of conventional ferromagnetic materials.     

Effect of Gd doping on electrical transport properties of La0.8Sr0.2MnO3 polycrystalline ceramics

Gd doped La_0.8Sr_0.2MnO₃ (La_0.8-xGd_xSr_0.2MnO₃, LGSMO) ceramics were prepared by a sol-gel method. X-ray diffraction (XRD) patterns showed that all samples exhibited distorted perovskite structures, R_3c. When the Gd³⁺ content x > 0.03, the crystal structure changed to orthorhombic, Pnma. Scanning electron microscopy (SEM) images showed that the ceramics characterize high density and grain boundary connectivity, and higher Gd³⁺ doping decreased the grain size from 26.72 μm to 7.42 μm. The temperature dependence of resistivity showed a transition from a low-temperature metal to a high-temperature insulator. The resistivity increased with Gd doping content, and the metal-insulator transition temperature, T_P, increased first and then decreased, while the temperature coefficient of resistance (TCR) of the samples first decreased and then increased with Gd³⁺, and the magnetoresistance (MR) increased first and then decreased. The peak TCR at x = 0.06 was 5.18%·K^?1, and MR at 0.04 was 34.57%. The electrical transport properties of the ceramics were explained based on the double exchange (DE) interaction mechanism. The obtained material may have application prospects in magnetic devices and infrared detectors.     

Growth and characterization of epitaxial (La2/3Sr1/3)MnO3 films by pulsed laser deposition

High quality epitaxial (La_2/3Sr_1/3)MnO₃ (0 0 1) thin films were grown by pulsed laser deposition on SrTiO₃ (0 0 1) substrate at optimized growth parameters. The films quality was confirmed by both structural and physical properties characterization. Channeling Rutherford Backscattering Spectrometry characterization showed the minimal channeling coefficient as low as 4%. The LSMO thin films growth on SrTiO₃ substrate follows the island growth model. The Curie temperature of LSMO films is around 360 K, which is the one of the highest reported in literature. The resistivity of LSMO films showed the metal-insulate transition temperature coincides with the Curie temperature. This high quality LSMO is suitable for room temperature magnetic devices application.     

Analysis on the microstructure and magnetic properties of MgGaFeO4 spinel compound

The single phase of the spinel ferrite MgGaFeO₄ is successfully prepared by the high-temperature solid-state reaction. The crystal structure, cation distribution, valence state, and magnetic properties are systematically investigated through various techniques in this work. From the analysis of X-ray diffraction, the face-centered cubic structure with the space group Fd3m for the single-phase sample is obtained. The magnetic hysteresis loops M(H) shows a typical magnetic hysteresis behavior at 5 K, while an obvious paramagnetic behavior can be observed at room temperature. The characteristics of magnetic properties suggest that the intrinsic ferromagnetic (FM) interaction and magnetic frustration are cooperated in the system. The specific divergence and irreversibility in the temperature-dependent magnetization curves M(T) indicate a typical spin-glass (SG) behavior, which occurring around the freezing temperature T_f = 40 K. Further analysis of the isothermal remanent magnetization (M_IRM) suggests the existence of an intensive magnetic frustration state, which leads to stable residual magnetization without decaying under a long time span. More than that, based on the corresponding fitting parameters (τ₀ = 8 × 10⁻¹² s, zv = 6.32 and T₀ = 56.2 K), the SG state in the sample is further confirmed. The following detailed analyses reveal that the competitions between antiferromagnetic (AFM) and ferromagnetic (FM) interactions definitely exist in MgGaFeO₄, which should be the response to motivate the SG behavior.     

Comparison of structure and multiferroic performances of bilayer and trilayer multiferroic heterostructures

This paper reports on the comparison of structure and multiferroic performances for Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃/La_0.7Sr_0.3MnO₃ (BCZT/LSMO) bilayer and BCZT/LSMO/BCZT trilayer multiferroic heterostructures. The epitaxial growth and the strain states of the multiferroic heterostructures are confirmed by the XRD RSM, which demonstrates that both the BCZT layer and LSMO layer in the trilayer heterostructure suffer larger residual strain than the bilayer one. The room temperature multiferroic nature of the multiferroic heterostructures is proved by the simultaneous observed ferroelectric and ferromagnetic properties as well as the magnetoelectric effect, which shows strong dependence of the residual strain. As compared with the trilayer heterostructure, the bilayer heterostructure shows better electrical and ferromagnetic properties as well as the ME effect. The largest piezoelectric coefficient of 40.5 p.m./V, the highest remnant polarization of 23.3 μC/cm² and the biggest ferromagnetic Curie temperature of 316.7 K are obtained in the bilayer heterostructure because of the smaller residual strain. And the bilayer heterostructure also shows the strongest magnetoelectric effect with the α_E31 value of 215.5 mV/cm·Oe.     

Complex Effect of Sm3+/W6+ Codoping on α‐β Phase Transformation and Phonon Scattering of Oxygen‐Deficient La2Mo2O9

Lanthanum molybdate, La₂Mo₂O₉, has been attracted considerable attention owing to its high concentration of intrinsic oxygen vacancies, which could be reflected by enhanced phonon scattering and low thermal conductivity. A new series of La₂Mo₂O₉‐based oxides of the general formula La_2?xSm_xMo_2?xW_xO₉, where x ≤ 0.2, were synthesized by citric acid sol–gel process. The variation in thermal conductivity with Sm³⁺and W⁶⁺ fractions was analyzed based on structure information provided by X‐ray diffraction and Raman spectroscopy. The fully dense La_2?xSm_xMo_2?xW_xO₉ ceramics showed a minimum thermal conductivity value [κ = 0.84 W·(m·K)^?1,T = 1073 K] at the composition of La_1.8Sm_0.2Mo_1.8W_0.2O₉, which stems from the multiple enhanced phonon scatterings due to mass and strain fluctuations at the La³⁺ and Mo⁶⁺ sites as well as the high concentration of intrinsic oxygen vacancies embedded in the crystal lattice. The thermal conductivities present an abrupt decrease at the structural transition, which is due to the phase transformation from a low‐temperature ordered form (monoclinic α‐La₂Mo₂O₉) to a high‐temperature disordered form (cubic β‐La₂Mo₂O₉₎.