Effect of oxygen content on magnetization and magnetoresistance properties of CMR manganites

The influence of oxygen content on the magnetization and electrical resistivity of Ln₀.₅A₀.₅MnO₃ (Ln=La,Pr,Nd; A=Ca,Ba) manganites with the perovskite structure is investigated. It is shown that the La₀.₅Ca₀.₅MnO₃₋γ compound undergoes a sequence of transitions from an antiferromagnetic (γ=0) to a spin-glass (γ=0.17) state and then to an inhomogeneous ferromagnetic (γ=0.3) state. A transition from an antiferromagnetic charge-ordered state to a ferromagnetic charge-disordered state in Nd₀.₅Ca₀.₅ MnO₃₋γ is observed as the oxygen content is reduced to where γ=0.07. The Nd₀.₅Ba₀.₅ MnO₃₋γcompound shows an increase of the Curie point from 110 K (γ=0) up to 310 K (γ=0.3). In addition, a large magnetoresistance is revealed which develops below their Curie temperature despite the absence of Mn³⁺√Mn⁴⁺ pairs. A Zener double-exchange interaction is usually used in literature to explain the magnetic and electrical properties of hole-doped perovskite manganites. The data obtained support the mechanism of superexchange interactions between magnetic moments of the manganese ions via oxygen

Critical properties of a ferroelectric superlattice described by a transverse spin-1/2 Ising model

The phase transition properties of a ferroelectric superlattice with two alternating layers A and B described by a transverse spin-1/2 Ising model have been investigated using the effective field theory within a probability distribution technique that accounts for the self spin correlation functions. The Curie temperature T-c, polarization and susceptibility have been obtained. The effects of the transverse field and the ferroelectric and antiferroelectric interfacial coupling strength between two ferroelectric materials are discussed. They relate to the physical properties of antiferroelectric/ferroelectric superlattices

Weak ferromagnetism in BiFeO3 doped with titanium

The Bi(1-x)A(x)Fe(1-x)Ti(x)O(3) (A-Ca, Sr, Pb, Ba) and BiFe1-xTixO3+delta systems have been studied using X-ray, neutron powder diffraction and magnetization measurements in a magnetic field up to 14 T. It was found that all Bi(1-x)A(x)Fe(1-x)Ti(x)O(3) solid solutions are rhombohedral up to x = 0.3. In the case of BiFe1-xTixO3+delta the rhombohedral distortion preserved up to x = 0.11. A homogeneous weakly ferromagnetic state was found for Bi1-xCaxFe1-xTixO3 (0.15 0.1 seem to be collinear antiferromagnets. (C) 2009 Elsevier B.V. All rights reserved.Belarussian Fund for Fundamental Research [T09-090

Electric-pulse-induced resistance switching effect in the bulk of La0.5Ca0.5MnO3 ceramics

In the majority of contributions, the electrical–pulse-induced resistance (EPIR) switching effect of perovskite manganites is thought to originate from the extrinsic interfacial Schottky barrier between the metal electrode and the surface of sample. In this work, La0.5Ca0.5MnO3 (LCMO) ceramic samples were synthesized by solid state reaction and the transport properties, especially, the EPIR effect and memristor behavior were investigated under 4-wire method using silver-glue as electrodes. Although the I-V characteristic of LCMO shows an ohmic linearity under the 4-wire mode at room temperature, a stable and remarkable EPIR can still be observed when the pulse voltage is more than a critical value. This bulk EPIR effect is novel for rare - earth doped manganites

Electric-pulse-induced resistance switching effect in the bulk of La 0.5

In the majority of contributions, the electrical–pulse-induced resistance (EPIR) switching effect of perovskite manganites is thought to originate from the extrinsic interfacial Schottky barrier between the metal electrode and the surface of sample. In this work, La0.5Ca0.5MnO3 (LCMO) ceramic samples were synthesized by solid state reaction and the transport properties, especially, the EPIR effect and memristor behavior were investigated under 4-wire method using silver-glue as electrodes. Although the I-V characteristic of LCMO shows an ohmic linearity under the 4-wire mode at room temperature, a stable and remarkable EPIR can still be observed when the pulse voltage is more than a critical value. This bulk EPIR effect is novel for rare - earth doped manganites

Effect of oxygen content on magnetization and magnetoresistance properties of CMR manganites

The influence of oxygen content on the magnetization and electrical resistivity of Ln₀.₅A₀.₅MnO₃ (Ln=La,Pr,Nd; A=Ca,Ba) manganites with the perovskite structure is investigated. It is shown that the La₀.₅Ca₀.₅MnO₃₋γ compound undergoes a sequence of transitions from an antiferromagnetic (γ=0) to a spin-glass (γ=0.17) state and then to an inhomogeneous ferromagnetic (γ=0.3) state. A transition from an antiferromagnetic charge-ordered state to a ferromagnetic charge-disordered state in Nd₀.₅Ca₀.₅ MnO₃₋γ is observed as the oxygen content is reduced to where γ=0.07. The Nd₀.₅Ba₀.₅ MnO₃₋γcompound shows an increase of the Curie point from 110 K (γ=0) up to 310 K (γ=0.3). In addition, a large magnetoresistance is revealed which develops below their Curie temperature despite the absence of Mn³⁺√Mn⁴⁺ pairs. A Zener double-exchange interaction is usually used in literature to explain the magnetic and electrical properties of hole-doped perovskite manganites. The data obtained support the mechanism of superexchange interactions between magnetic moments of the manganese ions via oxygen