12 research outputs found
Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry
In this paper we examine the role of crystal chemistry factors in creating
conditions for formation of magnetoelectric ordering in BiFeO3. It is generally
accepted that the main reason of the ferroelectric distortion in BiFeO3 is
concerned with a stereochemical activity of the Bi lone pair. However, the lone
pair is stereochemically active in the paraelectric orthorhombic beta-phase as
well. We demonstrate that a crucial role in emerging of phase transitions of
the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order
types belongs to the change of the degree of the lone pair stereochemical
activity - its consecutive increase with the temperature decrease. Using the
structural data, we calculated the sign and strength of magnetic couplings in
BiFeO3 in the range from 945 C down to 25 C and found the couplings, which
undergo the antiferromagnetic-ferromagnetic transition with the temperature
decrease and give rise to the antiferromagnetic ordering and its delay in
regard to temperature, as compared to the ferroelectric ordering. We discuss
the reasons of emerging of the spatially modulated spin structure and its
suppression by doping with La3+.Comment: 18 pages, 5 figures, 3 table
Physical and Numerical Simulation of Heat Transfer and Flow in Double-Cavity Diffuser-Type Dimples
Interaction of optical phonons with magnons in orthorhombic crystals and the effect of magnetic field on structural phase transitions
Neural Network Modeling of Thermal-Hydraulic Efficiency of Promising Surface Heat Transfer Intensifiers
Structural and magnetic phases of Bi 1−x Ax FeO 3− δ (A=Sr, Pb) perovskites
The Bi1-xAxFeO3-δ (A = Sr, Pb)
systems have been studied using the X-ray, neutron powder
diffraction and magnetization measurements in a magnetic field up to
14Â T. It was found that around x ~ 0.06 the crystal symmetry
changes from a rhombohedral (space group R3c) to
pseudo-tetragonal. In the composition range
0.07 ≤ x ≤ 0.14 the phases with different symmetry of
the unit cell coexist independent of synthesis conditions. The
neutron powder diffraction shows that the iron ions have average
oxidation state close to 3+. The magnetic structure for
Bi0.5Sr0.5FeO3-δ is found to be G-type
antiferromagnetic with magnetic moment of about
3.8 μB/Fe3+. The weak ferromagnetic state due to
magnetoelectric interactions was revealed in the lightly doped
rhombohedrally distorted compositions. No evidence for a spontaneous
magnetization was observed for the pseudo-tetragonal phases. These
compositions show irreversible nonlinear magnetization vs. field
behavior apparently due to small local deviations from the
collinearity of the magnetic moments.
Flexomagnetoelectric interaction in multiferroics
75.80.+q Magnetomechanical and magnetoelectric effects, magnetostriction, 75.50.Ee Antiferromagnetics,