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Superparamagnetic Properties of Ni0.7Zn0.3Fe2O4 Nanoparticles
Journal of Magnetics, Volume 10, Number 3, 30 Sep 2005, Pages 84-88
Abstract
Nanoparticles Ni0.7Zn0.3Fe2O4 is fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with XRD, SEM, Mössbauer spectroscopy, and VSM. Ni0.7Zn0.3Fe2O4 powders annealed at 300℃ have a spinel structure and behaved superparamagnetically. The estimated size of Ni0.7Zn0.3Fe2O4 nanoparticle is about 11 nm. Ni0.7Zn0.3Fe2O4 annealed at 400 and 500℃ has a typical spinel structure and is ferrimagnetic in nature. The isomer shifts indicate that the iron ions were ferric at the tetrahedral (A) and the octahedral (B). Blocking temperature (TB) of Ni0.7Zn0.3Fe2O4 nanoparticle is(TB) of Ni0.7Zn0.3Fe2O4 about 260 K. The magnetic anisotropy constant of (TB) of Ni0.7Zn0.3Fe2O4 annealed 300℃ were calculated to be 1.7×106 ergs/cm3. Also, temperature of the sample increased up to 43℃ within 7 minutes under AC magnetic field of 7 MHz.
Keywords: Superparamagnetism; Nanoparticle; Mössbauer spectroscopy; Magnetic anisotropy constant
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