Abstract
Single-phase lanthanum orthoferrite (LaFeO3) was prepared by an auto-combustion method. The analysis of synchrotron room temperature X-ray diffraction (XRD) data confirmed the orthorhombic LaFeO3 perovskite of space group Pnma without any impurity phase. The Scherrer's formula and Williamson-Hall plot based on XRD data were employed to estimate the crystallite size of the prepared sample. For a deeper insight into the crystal structure, high-resolution transmission microscopy imaging (HRTEM) was performed. The estimated values of crystallite size from HRTEM and synchrotron XRD data were coincident. The HRTEM images confirmed the polycrystalline nature of the prepared sample through the obvious lattice planes which are related to (121) plane. Furthermore, the M(H) hysteresis loop of the investigated sample was characterized by a vibrating sample magnetometer (VSM). The magnetic properties obtained through analyzing the magnetization versus temperature M(T) and magnetization versus magnetic field M(H) curves indicated that LaFeO3 possessed weak ferromagnetism at room temperature.
Highlights
Multiferroics are a group of smart materials that display ferroelectric and magnetic properties in a single phase; these materials are considerably rare compared to conventional classes of compositions
The crystallite size of the LaFeO3 sample was calculated by the X-ray line broadening method using the Scherrer's formula: D = kλ/βDcosθ [32], where D is the crystallite size in nanometers, λ is the beam wavelength (λ = 0.7 Å), k is a constant equal to 0.94, βD is the integral breadth, and θ is the peak position
We considered different possible spin magnetic orderings at the Fe3+ sites in the LaFeO3 structure and found that the ground state corresponds to an antiferromagnetic G-type ordering, as shown in Fig. 5, which agrees with the experimentally reported antiferromagnetic ordering at a Néel temperature of TN = 747 K [34]
Summary
Multiferroics are a group of smart materials that display ferroelectric and magnetic properties in a single phase; these materials are considerably rare compared to conventional classes of compositions. In LaFeO3, the 3d electrons configuration contributes to magnetic ordering of the transition metal ions within the material, resulting in lattice distortion due to the creation of a strong local electric field Due to this locally induced field, a ferroelectric arrangement is developed in this type of material. Among the rare-earth perovskites, lanthanum orthoferrite )LaFeO3) is a famous antiferromagnetic composition with a high Néel temperature (TN∼740 °C) [16,17] and possesses a distorted perovskite structure with a Pbnm (or Pnma) space group (SG) [18,19] due to tilting of the octahedral [FeO6] units This perovskite possesses high thermal stability and a well-defined structure. Orthorhombic structured LaFeO3 shows G-type weak antiferromagnetic ordering below 735 K and transitions to ferroelectric ordering at 475 K [20]
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