Modification induced by electronic excitation in CoFe2O4 thin films: Structural, morphological, and magnetic properties

The present study focuses on the modification induced by 200 MeV Ag¹⁵⁺ and 100 MeV O⁷⁺ ion irradiations on the structural, surface morphological, and magnetic properties of radio frequency sputtered CoFe₂O₄ (CFO) thin films grown on SiO₂/Si (100) substrates. X-ray diffraction shows amorphization of the CFO thin films when irradiated with Ag ions and varies with fluences. This effect is absent in the case of O ion irradiated CFO films. These results are consistent with the measurements from the Raman spectroscopy, where the intensities of E_g and T_2g modes are significantly reduced and further disappear in the high fluence. The surface morphology of the O ion irradiated films is dramatically different from the pristine and Ag ion irradiated films where the surfaces appear in nanopillars-like patterns. The topography of the O ion irradiated films appears to be like hill and valley structures, the roughness first increases (from 10.11 to 24.39 nm). Then it decreases to 18.93 nm on further increasing ion fluence. The coercivity, remnant magnetization, and saturation magnetization increase upon irradiation at low fluence 5 × 10¹¹ions/cm² for both the ion beams and then downturn with the increase of fluence 5 × 10¹²ions/cm². The changes in the magnetic and structural characteristics are ascribed to the defects induced by ion irradiation. These results are understood based on the structural and surface modifications induced by the electronic excitation of Ag and O ions. The study depicts that a controlled selection of ions and beam fluence can tailor the structure, morphology, and magnetic properties of ferrite films.