Schematic of the nanocluster deposition system. TMP indicates turbo molecular pump.
XRD spectrum of nanocluster film on MgO (M1-D) before and after irradiation. Both datasets are subtracted from their backgrounds. Inset text shows the crystallite sizes obtained from XRD line broadening.
(a) Helium ion micrograph of sample M1-D cross-section prior to Si2+ ion irradiation and (b) 3.0 MeV He+ RBS spectrum for the samples, together with simulation data (SIMNRA).
TEM micrographs of unirradiated (a,c) and ion irradiated (b,d) core-shell nanoparticles from sample M1-D. Fe core in (c) is ∼12 nm, and in (d)is ∼27 nm.
300 K magnetization (a) nanoclusters on Si; (b) close-up of near zero field region of (a); (c) and (d): effect of irradiation on (c) M1-D and (b) M2, where NC mass normalized curve indicated for irradiated sample.
First order reversal curve diagrams (300 K). (a) unirradiated 7 nm core with 2 nm Fe3O4 shell (#2); (b) unirradiated 10 nm core with 2 nm Fe3O4 shell (#4); (c) irradiated 7 nm core with 12 nm FeO “shell” (S2-i); and (d) irradiated single phase 23 nm Fe3O4 (S1-i).
Synthesis conditions for granular nanocluster films (aggregation distance was constant at 310 mm).
Crystalline phases and average crystallite sizes for granular films before and after irradiation. Parentheses indicate standard deviation in the last digit. Note that the irradiated values marked with asterisk (*) are the crystallite sizes, and given the TEM results should be understood to represent “matrix” crystallite size and not necessarily shell thickness, which they do for the unirradiated case (N/A is not applicable; “-” indicates quantity was not measured).
Details of the identified phases in the films before and after ion irradiation (-u = unirradiated; -i = irradiated).
Magnetic parameters at 300 K (#Saturation is defined as the 10 kOe data point. The sample still appears to have a small paramagnetic component, which was not removed. The diamagnetic component of the MgO was not removed either, but it is a very small effect. Note that the saturation and the remanence are normalized to the mass of the NC film only, and the Fe3O4 underlying film is not treated here. It should be noted that the total moment of the PLD Fe3O4 underlying film was <10% of the total moment (emu) of the combined system with NC for the thick PLD film and <1% of the total moment for the NC with thin PLD Fe3O4 film.).
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