Spin dynamics and criteria for onset of exchange bias in superspin glass Fe/γ-Fe2O3 core-shell nanoparticles

摘要: A detailed study is presented on Fe/γ -Fe2O3 core-shell structured nanoparticles (mean size ∼10 nm) to understand the spin dynamics of core and shell independently their role in triggering exchange bias (EB) phenomena. The particle critically slow down at Tg ∼ 68 K, below which they exhibit memory effect field-cooled zero-field-cooled protocols associated with a superspin glass state. field dependence mean blocking temperature fits de Almeida-Thouless line shows two different linear responses low high regimes corresponding shell, respectively. We show that energy barrier distribution estimated from decay isothermal remanent magnetization maxima mark freezing temperatures (Tf-cr 48 K) (Tf-sh 21 K). Last, hysteresis measurements after cooling reveal strong EB indicated by loop shift unidirectional anisotropy. onset 35 K when ferromagnetic frozen moments ferrimagnetic begin block, resulting enhanced coupling.