Abstract
Mixed ferrites Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 with orthorhombic perovskite structure isotypic with GdFeO3 were synthesized by solid-state reaction technique in air at 1473 K. Structural parameters obtained at room temperature prove a formation of continuous solid solutions in the SmFeO3–PrFeO3 and SmFeO3–NdFeO3 pseudo-binary systems. Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 show strongly anisotropic nonlinear thermal expansion: thermal expansion in the b direction is twice lower than in the a and c directions. The average linear thermal expansion coefficients of Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 in the temperature range of 298–1173 K are in the limits of (9.0–11.1) × 10−6 K−1, which is close to the values reported for the parent RFeO3 compounds. Subtle anomalies in the lattice expansion of Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 detected at 650–750 K reflect magnetoelastic coupling at the magnetic ordering temperature TN.
Highlights
Complex oxides with perovskite structure RFeO3, where R is the rare earth(RE), represent an important class of functional materials
X-ray powder diffraction examination revealed that both samples synthesized possess orthorhombic perovskite structure isotypic with GdFeO3
The unit-cell dimensions of Sm0.5Pr0.5FeO3 and Sm0.5Nd0.5FeO3 at room temperature are in good agreement with the structural data of the parent SmFeO3, PrFeO3 and NdFeO3 [14, 15] compounds, (Fig. 1), proving possible formation of continuous solid solutions Sm1 − xPrxFeO3 and Sm1 - xNdxFeO3 in the SmFeO3–PrFeO3 and SmFeO3–NdFeO3 systems
Summary
Complex oxides with perovskite structure RFeO3, where R is the rare earth(RE), represent an important class of functional materials. Complementary, the interest in the rare earth ferrites is stimulated by their interesting fundamental physical properties, such as spin-reorientation transitions at 80–480 K and the para- to antiferromagnetic transitions at 620–750 K [7,8,9,10]. The interest to RE ferrite perovskites was renewed due to reported multiferroic properties of NdFeO3, SmFeO3 and other RFeO3 compounds [11,12,13]. No structural phase transitions were reported in the literature for RFeO3 compounds, with an exception of LaFeO3, which undergoes a high-temperature (HT) transition to rhombohedral structure at 1220–1280 K [16, 17].
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