Magnetization Steps in Phase Separated La0.5Ca0.5Mn1−y Fe y O3

We report a low temperature magnetic study on the phase separated polycrystalline manganites La_0.5Ca_0.5Mn_1?y Fe _y O₃ (0.02≤y≤0.06). Several abrupt and sizeable magnetization steps are observed in the M(H) curves of all samples at 2 K, which are associated to avalanche-like growth of the ferromagnetic phase. This work contributes to confirm that this feature is inherent to phase separated manganites, and is not restricted to particular compounds or kinds of doping.     

Room temperature multiferroic properties of (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film

(Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film was prepared on a Pt(111)/Ti/SiO₂/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film. The (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film exhibited well saturated ferromagnetic (2 M_r of 18.1 emu/cm³ and 2H_c of 0.32 kOe at 20 kOe) and ferroelectric (2P_r of 60 μC/cm² and 2E_c of 813 kV/cm at 866 kV/cm) hysteresis loops with low order of leakage current density (4.5 × 10⁻⁶ A/cm² at an applied electric field of 100 kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.     

Enhanced room temperature multiferroic behaviour of Ni-doped Na0.5Bi0.5TiO3 ceramics

In this paper, room temperature multiferroic behaviour in Ni (Nickel)-doped NBT (Na_0.5Bi_0.5TiO₃) ceramics synthesized using solid state reaction technique have been investigated. Structural, dielectric, ferroelectric, magnetic and magneto-dielectric properties were consistently probed with the increment in transition metal doping. XRD peaks were indexed for the monoclinic Cc phase. SEM micrographs clearly depicted the reduction of grain size with addition of Ni content. Ferroelectric polarization (P) vs applied electric field (E) hysteresis curves shows an increase in lossy behaviour with an increase in Ni content. The room temperature magnetization (M) vs applied magnetic field (H) curves depict the weak ferromagnetic ordering on increasing the Ni doping. Enhanced magneto-dielectric change of 1.26% was observed in 25% Ni-doped NBT ceramic, which may be useful in the development of novel non-volatile lead-free multiferroic memory devices.

     

Comparison of Pb(Zr,Ti)O3 capacitors sandwiched with conductive La0.5Sr0.5CoO3 and non-conductive Bi3.25La0.75Ti3O12 layers

Ferroelectric capacitors of Bi_3.25La_0.75Ti₃O₁₂/PbZr_0.4Ti_0.6O₃/Bi_3.25La_0.75Ti₃O₁₂ (BLT/PZT/BLT) and La_0.5Sr_0.5CoO₃/PbZr_0.4Ti_0.6O₃/La_0.5Sr_0.5CoO₃ (LSCO/PZT/LSCO) are fabricated, respectively, on Si substrates in order to study the properties of PZT film sandwiched by conductive oxide and non-conductive oxide layers. It is found that the crystallinity of PZT film grown on LSCO electrode is much better than that on BLT film although the growth temperature of BLT/PZT/BLT is 100 °C higher than that of LSCO/PZT/LSCO. Remanent polarization of LSCO/PZT/LSCO capacitors measured at 10 V is 31.1 μC/cm², which is much higher than the value of 19.8 μC/cm² for BLT/PZT/BLT. Both kinds of the capacitors are fatigue-free up to 10¹⁰ switching cycles. The leakage current density measured at 5 V is about 4.7 × 10^− 6 A/cm² and 1.9 × 10^− 5 A/cm² for BLT/PZT/BLT and LSCO/PZT/LSCO, respectively. The differences for the two kinds of capacitors are discussed in the article.     

Structural and dielectric properties of La substituted polycrystalline Ca(Ti0.5Fe0.5)O3

Polycrystalline Ca_1?x La _x (Ti_0.5Fe_0.5)O₃ were prepared by the standard solid state reaction technique. Pellet shaped samples prepared from each composition were sintered at 1573 K for 5 h. The X-ray diffraction analysis indicated the formation of a single-phase orthorhombic structure. The lattice parameters as well as densities increased but the average grain sizes decreased with the increase of La content. The dielectric measurements were carried out at room temperature as a function of frequency and composition. The experimental results revealed that dielectric constant (?′) decreased but dielectric loss (tan δ) and ac electrical conductivity (σ _ac ) increased as frequency increased. The composition dependence of ?′ and tan δ indicated that they decreased with the increase of La content. The σ _ac was derived from the dielectric measurements and it is concluded that the conduction in the present samples is due to mixed polarons hopping.     

半掺杂Pr0.5Ca0.5Mn1-xCrxO3体系的电荷有序和磁电阻效应

研究了钙钛矿型半掺杂锰氧化物Pr0.5Ca0.5Mn1-xCrxO3(x=0、0.03、0.05、0.07、0.10)体系的输运性质、电荷有序和磁电阻效应.结果表明,Cr离子替代Mn位,增强了Pr0.5Ca0.5MnO3的铁磁性、金属电导和磁电阻值.在低掺杂情况下(x=0.03、0.05),Cr3 的掺杂使体系的铁磁性增强,当x＞0.05时(x=0.07、0.10),体系的铁磁性随x增大缓慢减弱.同时,随着掺杂量的增大,体系中的电荷有序相逐渐被抑制,磁电阻值也呈下降趋势,表明电荷有序相与磁电阻效应相关.Cr掺杂引起的各种磁耦合作用,包括Mn3 与Cr3 的铁磁双交换作用,Cr3 -Cr3 、Mn4 -Mn4 、Cr3 -Mn4 之间的反铁磁超交换耦合作用及相分离现象是产生上述结果的主要原因.     

Structural,vibrational and magnetic properties of Cu-substituted Mn0.5Zn0.5Fe2O4 nanoparticles

Journal of Materials Science: Materials in Electronics - Nanoparticles of quaternary Mn0.5?xCuxZn0.5Fe2O4 ferrite (x?=?0.05, 0.15, 0.25, and 0.35) have been investigated to...     

La3+掺杂Co0.5Ni0.5(Fe0.5Cr0.5)2O4尖晶石红外辐射材料的研究

用固相合成法制备La3+掺杂Co0.5Ni0.5(Fe0.5 Cr0.5)2O4尖晶石体系红外辐射材料,并通过DTA-TG、XRD和IRE-2型红外辐射测试等方法研究了材料的结构特征与红外辐射性能的关系,结果表明:随着La3+含量的增加,La3+以不同的形式进入Co0.5Ni0.5(Fe0.5 Cr0.5)2O4体系中,当La2O3掺杂浓度为5%(质量分数)时,样品的法向全波段辐射率达到0.91.     

La2O3、Y2O3掺杂对(Na0.5Bi0.5)0.94Ba0.06TiO3无铅压电陶瓷性能的影响

以(Na0.5Bi0.5)0.94Ba0.06TiO3为基体,研究了单、双组分掺杂La2O3、Y2O3对BNBT6陶瓷的压电和介电性能及微观结构的影响。XRD分析表明:掺杂La2O3、Y2O3均得到钙钛矿结构。SEM分析表明,分别掺杂0.2%La2O3和0.2%Y2O3使得陶瓷晶粒增大,压电常数提高,双组分掺杂La2O3、Y2O3在掺杂量0.12%La2O3+0.08%Y2O3时,压电常数d33增大到最大值144.6×10-12C/N,介质损耗降低到最小值0.039。     

Oscillating magnetoresistance of (Bi,Pb)2Sr2Ca2Cu3O x ceramics doped with Mn

The magnetoresistance nearT _c(T _cR=0=100 K) has been measured on ceramic samples of (Bi, Pb)₂Sr₂Ca₂(Cu_0.98Mn_0.02)₃O_x (X-Ray diffractions and measurements by a SQUID magnetometer give almost single 2223 phase) in magnetic fields, up to 60 kOe using a dc four-probe technique. We observed periodic oscillations superimposed on a monotonie growth of the magnetoresistance with the amplitude decreasing with increase in magnetic field. Fourier transforms of the magnetoresistance data gives two sharply pronounced periods, 10.7 and 14.7 kOe. Apparently these oscillations are connected with inhomogeneous distributions of Mn in superconducting grains with phase slippage at grain boundaries.     

Ferroelectric, electromechanical, and dielectric properties of (Na0.5Bi0.5)0.94Ba0.06TiO3 co-doped MnO2 and La2O3 lead-free ceramics

The modified (Na_0.5Bi_0.5)_0.94Ba_0.03La_0.02Ti_0.995Mn_0.005O₃ lead-free ceramics were prepared using a traditional solid-state reaction process, and their structures were characterized by X-ray diffraction, scanning electron microscope, and Raman spectroscopy, respectively. A double-like P–E loop was discussed at the room temperature for the co-doped ceramics by reason of the appearance of the anti-ferroelectric. The ferroelectric hysteresis loop and field-induced strain were studied at different temperatures. A large strain (S ₃₃ = 0.33 %, E = 50 kV/cm at 120 °C) was observed due to the transformation between ferroelectric and anti-ferroelectric phase at the phase transition temperature. Also, the depolarization temperature (T _d) of the co-doped ceramics was determined from the pyroelectric current density versus temperature plots, which was consistent with the result from the position of dielectric loss’s peak as a function of temperature.     

溶胶自燃烧法制备纳米Mn0.5Zn0.5Fe2O4和BaZn2Fe16O27粉体

以柠檬酸与硝酸盐为原料通过溶胶自燃烧法制备出纳米Mn0.5Zn0.5Fe2O4和BaZn2Fe16O27粉体.采用XRD、TG-DSC、TEM、AA、BET及VSM等方法对产物进行了表征,结果表明,在1000℃灼烧后分别得到了单相尖晶石型Mn0.5Zn0.5Fe2O4纳米粒子和六角磁铅石型BaZn2Fe16O27纳米粒子,其晶型完整,分散性好.     

La0.9Sr0.1MnO3/Fe2O3复合体系的异常磁电阻效应

采用软化学方法制备了不同粒径的La0.9Sr0.1MnO3和软磁材料γ-Fe2O3,并将两者按不同比例进行复合,分别用扫描电子显微镜和X射线技术观察了样品的形貌特征和相结构,发现掺杂后的复合体系的电阻率要远大于未掺杂样品的电阻率.掺入γ-Fe2O3后,样品表现出异常磁电阻效应,即加外磁场后样品的电阻率明显大于未加磁场时样品的电阻率.同时,掺杂样品磁电阻的磁场灵敏度显著提高,在室温附近观察到了磁电阻极大值.