Exchange bias in iron-oxide particles nanocasted in periodic porous Silica

Abstract

Iron-oxide nanoparticles were nanocasted in the periodic mesoporous silica matrix, consisting of two-dimensional hexagonally ordered channel system with the mean diameter of the channels about 7 nm. The magnetic measurements of dc magnetization confirm behavior typical of a superparamagnetic system, such as the irreversibility of the zero-field-cooled and field-cooled curves, presence of a maximum in zero-field-cooled curve related with blocking temperature T B and revealing of coercivity HC below TB. The existence of negative exchange bias efect below TB was confirmed in our system represented by value of exchange bias field HEB = -970 Oe measured at the temperature 2 K.