Synthesis, structure, and magnetic and dielectric properties of magnetoelectric BaDyFeO4 ferrite

Abstract BaDyFeO4 was prepared by a conventional solid-state method in air at 1573 K. It crystallizes in space group Pnma (No. 62) with a = 13.16861(1) A, b = 5.70950(1) A, and c = 10.26783(1) A, and it is isostructural with BaYFeO4. Three magnetic transitions were found in BaDyFeO4 at TN3 = 9 K, TN2 = 23 K, and TN1 = 47 K in zero magnetic field in comparison with two magnetic transitions observed in BaYFeO4. Magnetic-field-induced transitions were also detected in BaDyFeO4 at 18 and 28 kOe (at T = 1.8 K). Frequency-dependent broad dielectric peaks were observed in BaDyFeO4 spanning between TN2 and TN1 and centred at 35 K – this temperature does not coincide with any TN. No dielectric anomalies were found at TN1 and TN3, while very weak frequency-independent dielectric anomalies were detected at TN2. Positive and negative magnetodielectric effects were measured in BaDyFeO4 (within a range of −0.8 and + 0.4% up to 90 kOe) reflecting magnetic-field dependence of dielectric constant. Pyroelectric current measurements did not detect any ferroelectricity in BaDyFeO4 under measurement conditions used. No dielectric anomalies and no magnetodielectric effects were found in BaYFeO4.