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Keywords:

  • Ferromagnetic materials;
  • Magnetic materials;
  • Nanorods;
  • Phase transitions

Abstract

A series of ϵ-InxFe2–xO3 nanorods are prepared by combining the reverse-micelle and the sol–gel methods. Metal replacement was achieved in the region of 0 ≤ x ≤ 0.24. The crystal structures are orthorhombic structures (space group: Pna21), which are pyroelectric with an electric polarization along the c axis. The transmission electron microscopy images show that the particle sizes are (80 ± 40) × (23 ± 5) nm (x = 0), (65 ± 30) × (30 ± 10) nm (x = 0.12), and (80 ± 40) × (35 ± 15) nm (x = 0.24). The magnetization versus temperature curves of the samples with x = 0, x = 0.12, and x = 0.24 show spontaneous magnetization with Curie temperatures of 495 K, 456 K, and 414 K, respectively. Their coercive fields at 300 K are 20 kOe (x = 0), 14 kOe (x = 0.12), and 9 kOe (x = 0.24). These samples show a spin reorientation with reorientation temperatures (Tp) of 102 K (x = 0), 149 K (x = 0.12), and 180 K (x = 0.24). In particular, the samples with x = 0.12 and x = 0.24 show antiferromagnetic behavior below Tp. This series of ϵ-InxFe2–xO3 is the first example of a pyroelectric material that exhibits a phase transition between ferrimagnetism and antiferromagnetism.