Examination the Grain Size Dependence of Exchange Coupling in Oxide-Based SrFe12O19/Ni0.7Zn0.3Fe2O4 Nanocomposites

• Published in: Journal of superconductivity and novel magnetism Vol. 26; no. 7; pp. 2411 - 2417
• Main Authors: Radmanesh, S. M. A., Seyyed Ebrahimi, S. A.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-07-2013; Springer
• Subjects: Annealing; Characterization and Evaluation of Materials; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dispersion; Exact sciences and technology; Exchange and superexchange interactions; Ferrite; Grain size; Joining; Magnetic Materials; Magnetic properties; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetism; Nanocomposites; Original Paper; Physics; Physics and Astronomy; Strongly Correlated Systems; Studies of specific magnetic materials; Superconductivity; Transmission electron microscopy; Grain size; Nanocomposites; Hysteresis; Exchange-coupling; Temperature dependence; Hexagonal ferrites; Annealing; Oxides; Magnetic nanomaterial; Nanoparticles; Manganese phosphide; Magnetic particles; Composite materials; Iron Strontium Oxides Mixed; Magnetic materials; Sol-gel process; Exchange interactions; Magnetic properties
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-012-1819-3

Magnetic hard/soft SrFe
12
O
19
/Ni
0.7
Zn
0.3
Fe
2
O
4
nanocomposites were fabricated by a two-step chemical procedure. Strontium hexaferrite NPs were synthesized via sol–gel self-propagation and then dispersed in nickel–zinc ferrite sol to prepare oxide nanocomposites by the glyoxilate precursor method. The initial product was annealed at different temperatures to study the effect of grain size on the magnetic properties of composite hard/soft ferrites. The magnetic nanoparticles (MNPs) were characterized by XRD, FTIR, TEM, and VSM techniques. Magnetic measurements indicated concave hysteresis loops for these two-phase nanocomposites due to non-complete exchange coupling at the interfaces of hard and soft ferrites. This phenomenon could be attributed to the overcritical size, 46 nm, of the hard phase, based on the critical limit of 22 nm predicted by theoretical calculation. At high annealing temperature with increasing the size of the soft phase as well as the hard phase, the dipolar interaction became dominant and the magnetic behavior of hard/soft nanocomposites approached two-phase uncoupled magnets.