title: Effects of dipolar interaction on magnetic properties of Fe(x)(SiO2)1-x nanocomposites.
abstract: The effects of dipolar interaction on the magnetic properties of the Fe(x)(SiO2)1-x nanocomposites (22 wt% < or = x < or = 51 wt%) synthesized by mechanochemical reduction reaction have been studied by Mössbauer spectroscopy and magnetic measurements. As the average particle size of the Fe particles in the Fe(x)(SiO2)1-x nanocomposites changes very little with increasing Fe content x, the dipolar interaction strength can be tuned by adjusting the distance between the Fe particles through controlling the Fe content x. Thus the effects of dipolar interaction on the magnetic properties of the Fe(x)(SiO2)1-x nanocomposites can be clearly studied. Due to the dipolar interaction, the Fe particles transit from superparamagnetic state to the blocked state. With x increasing from 22 wt% to 48 wt%, due to dipolar interaction, the Fe particle moment arrangements change from random orientation to ordered arrangements, which induced an additional anisotropy, leading to the increase in the coercivity H(c) and remanence ratio M(r)/M(s). For x increasing beyond 48 wt%, the dipolar interaction strength further increases, and the Fe particle moment arrangements tend to form the flux-closure configurations in order to reduce the dipolar interaction energy among the particles, which result in the decreases of H(c) and M(r)/M(s) with increasing x.
authors.affiliation: Institute of Materials Science and Engineering, MOE Key Laboratory for Magnetism and Magnetic Materials, Lanzhou University, Lanzhou 730000, China.
authors.forename: Ji
authors.initials: J
authors.lastname: Ma
authors.forename: Xia
authors.initials: X
authors.lastname: Ni
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Huang
authors.forename: Jiangong
authors.initials: J
authors.lastname: Li