Nanocrystalline orthoferrite powders: Synthesis and magnetic properties

• Published in: Journal of the European Ceramic Society 2006, Vol.26 (16), p.3675-3679
• Main Authors: Rajendran, M., Bhattacharya, A.K.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Ferrites; LaFeO 3; Magnetic properties; Magnetic properties and materials; Magnetic properties of nanostructures; Materials science; Nanocrystalline powders; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Physics; Sol–gel processes
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2006.01.008

Nanocrystalline orthoferrite powders were synthesised at low temperatures by employing an aqueous sol–gel process. Colloidal sols and water re-dispersible gels of orthoferrite precursors were prepared by room-temperature processing of inexpensive metal salts. The average diameter ( Z av) of the precursor particles was in the size range from 4 to 7 nm; the diameters had a narrow size distribution. Water re-dispersible translucent gel monoliths were obtained by concentrating the aqueous sols followed by drying them under reduced pressure (10 −2 Torr) at room temperature. The sol–gel transition was found to be completely reversible. Nanocrystalline fine powders of orthoferrites of general formula, LnFeO 3 (Ln = La, Sm, Gd, Dy, Er, Yb and Y) having a crystallite size of about 25 nm were prepared by heating the gel precursors at 650–700 °C in air. Powder X-ray diffraction and thermogravimetry, respectively, were employed to identify perovskite phase formation and delineate thermal events that lead to gel to crystallite conversion. Magnetic measurements were carried out on the resultant powders at room temperature and down to 40 K. Nanocrystalline orthoferrite powders exhibited weak ferromagnetic behaviour, and reduced magnetic moments.