186 research outputs found
Antiferromagnet-ferromagnet phase transition in lightly doped manganites
Magnetic and structural phase diagrams of the La₀.₈₈MnOx, La₁₋xSrx(Mn₁₋x/₂Nbx/₂)O₃,
Nd₁₋xCaxMnO₃, and Bi₁₋xCaxMnO₃ series constructed on the basis of x-ray, neutron powder diffraction,
Young’s modulus, magnetization and resistivity measurements are presented. It is shown
that the main factor controlling the antiferromagnet–ferromagnet phase transition in the manganites
is a type of an orbital state. The results are discussed in the framework of structurally driven
magnetic phase separation model
Selective dilution and magnetic properties of La_{0.7}Sr_{0.3}Mn_{1-x}M'_xO_3 (M' = Al, Ti)
The magnetic lattice of mixed-valence Mn ions in LaSrMnO
is selectively diluted by partial substitution of Mn by Al or Ti. The
ferromagnetic transition temperature and the saturation moment decreases with
substitution in both series. The volume fraction of the non-ferromagnetic
phases evolves non-linearly with the substitution concentration and faster than
theoretically expected. By presenting the data in terms of selective dilutions,
the reduction of is found to be scaled by the relative ionic
concentrations and is consistent with a prediction derived from molecular-field
theory.Comment: 6 pages, 5 figures, REVTex4.0. Submitted to PR
Orbital ordering and enhanced magnetic frustration of strained BiMnO3 thin films
Epitaxial thin films of multiferroic perovskite BiMnO3 were synthesized on
SrTiO3 substrates, and orbital ordering and magnetic properties of the thin
films were investigated. The ordering of the Mn^{3+} e_g orbitals at a wave
vector (1/4 1/4 1/4) was detected by Mn K-edge resonant x-ray scattering. This
peculiar orbital order inherently contains magnetic frustration. While bulk
BiMnO3 is known to exhibit simple ferromagnetism, the frustration enhanced by
in-plane compressive strains in the films brings about cluster-glass-like
properties.Comment: 8 pages, 4 figures, accepted to Europhysics Letter
Electromechanical and magnetic properties of BiFeO3-LaFeO3-CaTiO3 ceramics near the rhombohedral-orthorhombic phase boundary
BiFeO3-LaFeO3-CaTiO3 ceramics have been studied by X-ray diffraction, magnetization measurements, and piezoresponse force microscopy (PFM). The compositional ranges of the polar, antipolar, and non-polar phases have been estimated. PFM measurements testify gradual decrease of piezoelectric response in Bi(0.85-x)La(0.15)CaxFe(1-x)Ti(x)O(3) system with Ca/Ti content increase, except a narrow concentration region near polar-antipolar phase boundary where piezoelectric signal shows maximum value. It is found that increase of dopant concentration leads to apparent decrease of the off-center Bi-O displacement and, consequently, causes a reduction of piezoelectric response. It is concluded that notable remanent magnetization in polar and non-polar structural phases is a result of the Dzyaloshinsky-Moria interaction. (C) 2013 AIP Publishing LL
Pressure effect on magnetic susceptibility of LaCoO
The effect of pressure on magnetic properties of LaCoO is studied
experimentally and theoretically. The pressure dependence of magnetic
susceptibility of LaCoO is obtained by precise measurements of
as a function of the hydrostatic pressure up to 2 kbar in the
temperature range from 78 K to 300 K. A pronounced magnitude of the pressure
effect is found to be negative in sign and strongly temperature dependent. The
obtained experimental data are analysed by using a two-level model and DFT+U
calculations of the electronic structure of LaCoO. In particular, the fixed
spin moment method was employed to obtain a volume dependence of the total
energy difference between the low spin and the intermediate spin
states of LaCoO. Analysis of the obtained experimental dependence
within the two-level model, as well as our DFT+U calculations, have revealed
the anomalous large decrease in the energy difference with increasing
of the unit cell volume. This effect, taking into account a thermal expansion,
can be responsible for the temperatures dependence of , predicting its
vanishing near room temperature.Comment: 7 pages, 9 figure
First Principles Investigation of Ferromagnetism and Ferroelectricity in Bismuth Manganite
We present results of local spin density approximation (LSDA) pseudopotential
calculations for the perovskite structure oxide, bismuth manganite (BiMnO3).
The origin of the differences between bismuth manganite and other perovskite
manganites is determined by first calculating total energies and band
structures of the high symmetry cubic phase, then sequentially lowering the
magnetic and structural symmetry. Our results indicate that covalent bonding
between bismuth cations and oxygen anions stabilizes different magnetic and
structural phases compared with the rare earth manganites. This is consistent
with recent experimental results showing enhancement of charge ordering in
doped bismuth manganite
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