Cobalt nanoclusters in silica glass: Nonlinear optical and magnetic properties

Abstract

Fused silica plates were implanted with Co ions at room temperature at the energy of 50 keV and to the fluence of 4×1016 ions cm−2. The formation of metal nanoclusters was observed by transmission electron microscopy. The cluster size distribution is narrow with a mean-diameter value of about 3 nm. Atomic in-depth distribution was determined by Rutherford backscattering spectrometry, whereas the cobalt chemical state was characterized by electron spectroscopies. Nonlinear refractive index n2 is of the order of 0.2 cm2 G W−1, as determined by the Z-scan technique at a wavelength of 770 nm for 130 fs long pulses at a 76 MHz repetition rate. Zero-field-cooled and field-cooled magnetization curves at the liquid-helium temperature exhibit features of superparamagnetic behavior that are characteristic of assemblies of single-domain nanoparticles.

Nanocomposite Materials Formed by Ion Implantation

“…In one recent example, Co nanoparticles were produced by implantation of silica glass plates (50, 4 10 16 , 30 C). [92] This produced a~90 nm thick layer of randomly oriented Co precipitates near the surface of the specimen. Zerofield-cooled and field-cooled susceptibilities were measured and indicated a blocking temperature of~20 K. Above the blocking temperature, the particles are superparamagnetic.…”

Theory of Nanocluster Size Distributions from Ion Beam Synthesis

“…The deposition of energetic ions fragments the clusters, leads to inverse Ostwald ripening [9], and ultimately limits cluster sizes. The basic understanding of IBS has been exploited to fabricate interesting nanostructures [9][10][11][12][13][14][15] and alter cluster size distributions [15,16]. But unlike low dose semiconductor doping via implantation that is extensively studied and understood [17][18][19][20], no detailed, comprehensive, quantitative theory if IBS has been developed.…”

Structural and magnetic properties of sputter deposited cobalt–silica nanocomposite thin films

“…Within single domain particle magnetic moments flip all together as a supermoment between easy magnetization axes when thermal energy is larger than the anisotropy energy barrier. Thus the magnetic behavior of an ensemble of this kind of single-domain particles is paramagnetic-like [8][9][10]. It is well known that paramagnetic nanoparticles are not suitable as memory storage since thermal fluctuations result in losing stored data.…”

“…The studies on magnetic properties of sputter deposited Co-SiO 2 thin films are limited in the literature [14,15]. However study of Co-SiO 2 system synthesized by other techniques like sol-gel and ion implantation has been done by several authors [6][7][8][16][17][18][19][20][21][22]. Therefore, the present work is focused on to fabricate Co-SiO 2 nanocomposite films by using DC/RF magnetron co-sputtering and investigate the effect of cobalt concentration on their magnetic behavior.…”