Control of magnetization in spinel-type Fe₃O₄ thin films by N₂ ion implantation

Abstract

The magnetism of a typical spinel ferromagnetic oxide, Fe3O4, was controlled via ion implantation. Nitrogen ions were accelerated at 6–10 kV and irradiated to the 13-nm-thick Fe3O4 thin films with dosages of 2 × 1016 to 6 × 1016 ions/cm2. The magnetization decreased with the increase in ion dosage, and there was almost no magnetization when 6 × 1016 ions/cm2 of nitrogen was irradiated, irrespective of the acceleration voltages. The results of the temperature dependence of the magnetization and the Mössbauer study suggest that the transition from ferromagnetic to nonmagnetic phases in the Fe3O4 thin film upon N2 ion irradiation proceeds abruptly without the formation of intermediate states.

Magnetization control for bit pattern formation of spinel ferromagnetic oxides by Kr ion implantation

“…These suggest that the ferromagnetic components in the ion-implanted films have an almost uniform magnetic transition temperature throughout the layer, similar to the N 2 -implanted case. 13 Our TEM observations support the evidence for this similarity in their microstructure.…”

“…3, together with the corresponding data for N 2 irradiation. 13 It decreases with the increase in dosage and reaches almost zero at dosage of 2 Â 10 15 , which is much smaller than the value for N 2 ion irradiation, 6 Â 10 16 ions/cm 2 . The Fe content estimated from XRF data was almost constant through the Kr ion implantation.…”

“…Previously, we demonstrated the effectiveness of N 2 ion implantation in magnetization control in these materials. 13 In this paper, we report our efforts to control the magnetization of the "typical" spinel ferromagnetic oxide, Fe 3 O 4 , using Kr ion irradiation. Gathering these results is the first step toward the synthesis of nanopatterned oxide magnetic materials for use in storage devices.…”

“…Solid circles and open circles show the magnetization for the samples with C coated and without C coated layer, respectively. Closed squares show the magnetization of the sample with C coated layer irradiated by N 2 ions 13.…”

Process–structure–property relationships in nanocomposites based on piezoelectric-polymer matrix and magnetic nanoparticles

“…The nanoparticles of Fe 3 O 4 exhibit super paramagnetism when their particle size is below 10-30 nm, i.e., smaller than the average size of magnetic domains (Lu et al, 2007;Gawande et al, 2013;Kita et al, 2014;Castellanos-Rubio et al, 2014;Qi et al, 2013;Zou et al, 2014;Gage et al, 2013). Super paramagnetism is governed particularly by a magnetization reversal mechanism for fine particles driven by the thermal energy.…”