ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Granular Fe-SiO2 thin films were prepared by low rate (∼0.3 A(ring)) sputtering onto substrates rotating above separate Fe and SiO2 targets. Thin silicon nitride "windows'' in the substrates permitted transmission electron microscopy measurements on the same films characterized by other techniques. Low Fe concentration, nonpercolating films contained well dispersed ∼40 A(ring) spheres of pure Fe with a narrow size distribution, as previously reported for granular films prepared from separate sources.1 Although Hc showed a strong temperature dependence, as did films prepared at high sputtering rates from a single composite target, the other magnetic properties of these films were very different. The maximum Hc values at 4.2 K were much lower. The peak in Hc occurred at a significantly lower vol % Fe. The hysteresis loops were square with remanence ratios (approximately-greater-than)0.90 at temperatures between 4.2 and 296 K. Furthermore, Lorentz micrographs taken at 296 K showed stable domain structures and ripple patterns. This strong evidence for cooperative magnetic behavior is difficult to reconcile with arrays of nonpercolating particles far above their nominal blocking temperatures. The possible role of dipolar and exchange interactions among these particles will be discussed.2〈ks〉
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.348049
