title: The origin of the non-monotonic field dependence of the blocking temperature in magnetic nanoparticles.
abstract: The dependence of the peak temperature (T(P)) of the zero-field-cooled (ZFC) magnetization curves on the field in a magnetic nanoparticle system was studied using a diluted magnetic fluid composed of FePt nanoparticles. We found that the peak temperature increases with increasing applied field below 3 kOe; it then decreases when the applied field is increased further. We attribute the non-monotonic field dependence of the peak temperature to the anisotropic energy barrier distribution of the particles and to the slow decrease of high-field magnetization above the blocking temperature. Numerical simulations, based on magnetic dynamics, agree well with our experimental results.
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China.
authors.forename: R K
authors.initials: RK
authors.lastname: Zheng
authors.forename: Hongwei
authors.initials: H
authors.lastname: Gu
authors.forename: Bing
authors.initials: B
authors.lastname: Xu
authors.forename: X X
authors.initials: XX
authors.lastname: Zhang