Magnetic properties of cobalt substituted M-type barium hexaferrite prepared by co-precipitation

• Published in: Journal of magnetism and magnetic materials Vol. 312; no. 2; pp. 418 - 429
• Main Authors: Mallick, Kajal K., Shepherd, Philip, Green, Roger J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-05-2007; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Electrical property; Electron microscopy; Exact sciences and technology; Ferrite; Magnetic properties and materials; Magnetic property; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Physics; Magnetic property; Electrical property; Ferrite; Electron microscopy; Hexagonal ferrites; Curie point; Magnetization; Doping; Thermogravimetry; Magnetic hysteresis; Differential thermal analysis; XRD; Iron loss; Synthesis; Magnetic permeability; Barium oxides; Iron oxides; Coprecipitation; Magnetic properties
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2006.11.130

The co-precipitation and solid state methods were used in the synthesis of barium hexaferrite (BaM). Phase pure BaM was obtained with 1, 2, 3, 5, 10, 15, 20 and 30
wt% cobalt oxide (Co
3O
4). The addition of Co
2+/3+ ions to the BaM increased the permeability and magnetic loss tangent to a value of 3.5 at 5% and reduced to 1 at 30% doping. With increased Co doping,
M
s was reduced from 87-58
emu/g,
M
r increased from 11 to 40
emu/g with 3–5
wt% Co and 9
emu/g for 30% doping.
H
c sharply increased from 540 to 2200
Oe with a reduction to 280
Oe at 10
K with increasing temperature to 300
K.
T
c increased from 740 to 750
K for 30% Co doping. DTA–TGA studies of green body showed decarboxilation to occur at around 825
°C and the transformation of residual Co
3O
4 to Co
2O
3 at around 577
°C. The XRD data confirmed the Co ions substituting into Fe sites until a 10–15% doping level where the structure altered to W-type hexaferrite. The densities of the compounds varied with doping to a maximum of 4.45 g/cm
3.