Abstract
The structural, magnetic, and dielectric properties of ceramic samples of Yb-doped PbFe2/3W1/3O3 have been investigated by a variety of methods including x-ray powder diffraction, magnetometry, and dielectric spectroscopy. In addition, theoretical investigations were made using first-principles density functional calculations. All the doped samples Pb(Fe1 − xYbx)2/3W1/3O3 (PFYWO) (0.1 ≤ x ≤ 0.5) were found to crystallize in an ordered cubic (Fm3¯m) structure with partial ordering in the B-perovskite sites. Observed changes in the cationic order were accompanied by differences in the dielectric and magnetic responses of the system. While pure PbFe2/3W1/3O3 is antiferromagnetic, the doped Pb(Fe1 − xYbx)2/3W1/3O3 PFYWO samples display excess moments and ferrimagnetic-like behavior, associated with differences in B′ and B″ site occupancies of the magnetic Fe3+ cations. The magnetic transition temperature of the ferrimagnetic phase is found to decrease with increasing Yb content, from TN ∼350 K of the undoped sample down to 137 K for x = 0.5. All PFYWO compounds display a ferroelectric relaxor behavior akin to that of PbFe2/3W1/3O3, albeit our results show significant changes of the frequency and temperature dependence of the dielectric properties. The changes of the properties of PFYWO with increasing Yb substitution can be explained by the changes in the cation size/charge mismatch and the size difference of the two ordered positions.
Highlights
PbFe2/3W1/3O3 (PFWO) was the first reported MF material in the double perovskite family PbB32+/3B61+/3O3.12 The initial idea behind the preparation of PFWO was based on the search for ferrimagnetic perovskites with some kind of order of the B-site cations creating two sublattices corresponding to the formula Pb[Fe]0.5[Fe1/3W2/3]0.5O3
Structural refinements of the X-ray powder diffraction (XRPD) powder diffraction patterns of Pb(Fe1 − xYbx)2/3W1/3O3 (PFYWO) with x < 0.1 confirm that these samples stabilize in the cubic Pm3m symmetry at room temperature
Cationic order was observed over the full concentration range of Yb susbstitution (0.1 ≤ x ≤ 0.5)
Summary
Studies of dielectric and magnetic properties of Pb-based perovskites have revealed several new multiferroic (MF) materials. The consequences and cause of cationic order on the B-site in such perovskites have been discussed in the literature. Ionization potentials, cation coordination geometry, and the A-cation/B-cation size ratio are factors that influence the degree of ordering. PbFe2/3W1/3O3 (PFWO) was the first reported MF material in the double perovskite family PbB32+/3B61+/3O3.12 The initial idea behind the preparation of PFWO was based on the search for ferrimagnetic perovskites with some kind of order of the B-site cations creating two sublattices corresponding to the formula Pb[Fe]0.5[Fe1/3W2/3]0.5O3. The consequences and cause of cationic order on the B-site in such perovskites have been discussed in the literature.. PbFe2/3W1/3O3 (PFWO) was the first reported MF material in the double perovskite family PbB32+/3B61+/3O3.12 The initial idea behind the preparation of PFWO was based on the search for ferrimagnetic perovskites with some kind of order of the B-site cations creating two sublattices corresponding to the formula Pb[Fe]0.5[Fe1/3W2/3]0.5O3. In this case, the magnetic moments of two sublattices directed oppositely to each other are not compensated, and the ferroelectric material becomes ferrimagnetic. PFWO is a Pb-based 2:1 perovskite that combines magnetically active Fe3+ cations and ferroelectrically active W6+ cations.
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