1/f noise studies of swift heavy ion irradiated magnetite thin films

Abstract

The effect of 190MeV 107Ag ion irradiation on antiphase boundaries (APBs) of epitaxial Fe3O4 thin films (thickness ∼70nm) grown on MgO (100) oriented substrate has been investigated. The X-ray diffraction shows that at low fluence values upto 5×1011ions/cm2, the strain in the films is relaxed whereas at high fluence 1×1012ions/cm2, the epitaxial relationship with the substrate is decreasing. The low frequency conduction noise (1/f noise) and electrical transport properties are found to depend on the value of ion fluence. The variation in Verwey transition temperature (Tv) has been observed for low fluence, but it disappears at higher fluence (1×1012ions/cm2). In the low fluence regime the Sv (V2/Hz) decreases which is an evidence of the decrease in density of APBs. But higher fluence creates disorder in the system and hence increase in Sv and the density of APBs. The conduction noise is proportional to the square of the bias current (Sv∝I2) for all films at room temperature, which confirms that the noise arises from the conduction fluctuations. On the basis of our observations we conclude that the strain created due to swift heavy ion (SHI) irradiation plays a major role in controlling the density of APBs.