Magnetic Properties Of Perovskite Research Articles

Existence of Magneto-Resistance and Magneto-Dielectric Effect in Composite of Perovskite Pb0.79Nd0.21TiO3 and Sr -Based U-Type Hexaferrite (Sr1–3xNd2x)4Co2Fe36O60

The increasing demand of multipurpose equipment materials leads us to study the behaviour of composite consisting of ferroelectrics with high dielectric properties and ferrites with magnetic properties. The coupling among the properties of these materials with one another will favor many application paths. Based upon the dielectric and magnetic properties of perovskite and U-type hexaferrite, composite of these materials have been selected for this study. The composites, (1-x)PbNdTiO3-x(Sr1–3x Nd2x )4Co2Fe36O60 where x = 0.42, 0.44, 0.46, 0.48 are manufactured using the solid state reaction process, and analyzed for phase formation. The magnetic, dielectric and magneto-dielectric properties have been considered. The coupling between the electric and magnetic domains on imposing electric and magnetic forces on the materials has been established under this work. All of the samples showed magneto-electric coupling, according to the magneto-dielectric investigation. The sample, however, indicates the highest coupling for x = 0.46 with MDR% values of 90.68% which may be due to the appearance of high magneto-resistance (68.23%) in this sample.

Cu powder doping effects on the structure and electro-magnetic properties of La0.7Ca0.3MnO3

The structure, electronic and magnetic properties of perovskite (1 − x)La0.7Ca0.3MnO3(LCMO)/xCu (x is a mass percentage, x = 1%, 3%, 5%, 7%, 9%, 15%, 20%) have been studied. The nano-scale metal Cu powder was doped into the LCMO matrix. The results showed that some Cu element substituted for Mn ion in LCMO and the remainder resided in the grain boundaries in the form of a CuO phase because of the oxidation process when the Cu powder was sintered at high temperature in air. Cu existed in the form of Cu3+ ions in the samples at a low doping level (x ⩽ 3%) and Cu2+ ions appeared when x > 3%. Because of the larger ionic radius of Cu2+ ions compared with the average Mn radius, it is likely that the Cu2+ ions in the proximity of the grain boundaries tend to separate into the boundaries. An amorphous phase of the Cu element was formed in the grain boundaries, which respond to the unusual electrical and magnetic behaviours of the heavily doped samples. A maximum MR value (∼50%) around 210 K was observed in a magnetic field of 3000 Oe for the 5% doped samples. Besides the effect of Cu substituting for Mn ions in LCMO, the MR behaviour is also attributed to the properties of dopants which reside in the grain boundaries of the matrix grains.

Electrical and magnetic properties of perovskite at low temperature

Electrical and magnetic properties of have been extensively investigated at low temperature down to 1.8 K. The irreversibility of magnetic susceptibility between zero field cooling and field cooling increases with increasing Y content. The metal-insulator transition temperature shifts towards lower temperature and the peak resistivity and magnetoresistance increase with the increase of x. Electrical conduction above is dominated by the variable range hopping mechanism. The increase in resistivity at low temperature has been interpreted in terms of electron-electron interaction. The enhancement of magnetoresistance with the increase of Y content is due to the reduction in Mn-O-Mn bond angle and the mobility of charge carriers.

A quantum mechanical investigation of the electronic and magnetic properties of perovskite

The ground-state electronic structures of ferromagnetic and antiferromagnetic perovskite in the ideal cubic phase have been investigated using the ab initio periodic Hartree - Fock approach. The system is a wide-gap insulator. The antiferromagnetic phase is correctly predicted to be the more stable (0.07 eV per Mn atom at the equilibrium geometry), but the superexchange interaction is substantially overestimated. The energy difference between the two phases increases slowly and linearly under compression, at variance with that for , that shows an exponential behaviour when the M - M distance is reduced. As regards the electronic structure, three unpaired electrons occupy very localized -type d orbitals on Mn. About 1.8 electrons (according to a Mulliken partition scheme for the electronic charge) occupy Mn -type states ( and Mn d orbitals), which however overlap significantly with oxygen p orbitals; the degree of spin polarization of these bond states is very low. The electronic structure of the system is discussed in terms of the density of states and charge- and spin-density maps.

Magnetic properties of perovskites R(Mn0.5A0.5)O3 (R = Nd, Eu; A = Co, Ni)

The magnetic properties of perovskites R(Mn0.5A0.5)O3 (R = Nd, Eu; A = Co, Ni) are reported. It is shown that these compounds are ferromagnets with relatively high Curie temperature. The magnetic anisotropy of the Ni-containing perovskites is much less than that for the Co-containing ones. Magnetic measurement data are interpreted assuming the charge state of cations to be Co2+(Ni2+) and Mn4+ and the ferromagnetism to be governed by superexchange interactions between the Co(Ni) and the Mn ions.