Incoherent magnetization reversal in 30-nm Ni particles

Integrating magnetic functionalities with silicon holds the promise of developing, in the most dominant semiconductor, a paradigm-shift information technology based on the manipulation and control of electron spin and charge. Here, we demonstrate an ion implantation approach enabling the synthesis of a ferromagnetic layer within a defect free Si environment by exploiting an additional implant of hydrogen in a region deep below the metal implanted layer. Upon post-implantation annealing, nanocavities created within the H-implanted region act as trapping sites for gettering the implanted metal species, resulting in the formation of metal nanoparticles in a Si region of excellent crystal quality. This is exemplified by the synthesis of magnetic nickel nanoparticles in Si implanted with H+ (range: ∼850 nm; dose: 1.5 × 1016 cm−2) and Ni+ (range: ∼60 nm; dose: 2 × 1015 cm−2). Following annealing, the H implanted regions populated with Ni nanoparticles of size (∼10–25 nm) and density (∼1011/cm2) typical of those achievable via conventional thin film deposition and growth techniques. In particular, a maximum amount of gettered Ni atoms occurs after annealing at 900 °C, yielding strong ferromagnetism persisting even at room temperature, as well as fully recovered crystalline Si environments adjacent to these Ni nanoparticles. Furthermore, Ni nanoparticles capsulated within a high-quality crystalline Si layer exhibit a very high magnetic switching energy barrier of ∼0.86 eV, an increase by about one order of magnitude as compared to their counterparts on a Si surface or in a highly defective Si environment.

Section: Implications On Magnetic Anisotropy and Particle Interactsupporting

confidence: 60%

Section: Implications On Magnetic Anisotropy and Particle Interactmentioning

confidence: 99%

Synthesis and properties of ferromagnetic nanostructures embedded within a high-quality crystalline silicon matrix via ion implantation and nanocavity assisted gettering processes

Malladi

Huang

Murray

et al. 2014

“…2͑b͒ and 2͑c͒ cannot be explained through coherent magnetization rotation. Indeed, computer simulations by Ross et al 15 and Nielsch et al 16 show that the magnetization process in the nanostructures is evidently different from the abrupt coherent magnetization reversal predicted by SW model. For the nanostructures with small aspect ratio, the magnetization occurs through incoherent magnetization reversal, 15 whereas in nanowires domain walls nucleate at the ends of the wires and propagate along the wires.…”

Section: Resultsmentioning

confidence: 99%

“…Indeed, computer simulations by Ross et al 15 and Nielsch et al 16 show that the magnetization process in the nanostructures is evidently different from the abrupt coherent magnetization reversal predicted by SW model. For the nanostructures with small aspect ratio, the magnetization occurs through incoherent magnetization reversal, 15 whereas in nanowires domain walls nucleate at the ends of the wires and propagate along the wires. 16 A Mi-Ha AAM with large interpore distance of 250 nm was synthesized in order to check the effect of magnetostatic interactions among the nanowires, compared with regular membranes with about 100 nm interpore separations.…”

Section: Resultsmentioning

confidence: 99%

Fabrication and magnetic properties of Fe nanostructures in anodic alumina membrane

Lim

Chae

Lee

et al. 2010

Several Fe nanostructures with different lengths, diameters, and separations of the constituting magnetic components have been synthesized using anodized alumina membranes ͑AAMs͒ to understand the influence of these parameters on their magnetic properties. Fe nanostructures with high crystallinity and ͑110͒ orientation were synthesized by electrodeposition at room temperature in regular AAMs and mild-hard AAM ͑Mi-Ha AAM͒. Fe nanostructures with different aspect ratios ͑1:1, 1:10, and 1:75͒ in the form of nanodots, nanorods, or nanowires were synthesized in regular AAMs with the 100 nm interpore distance. Mi-Ha AAMs with two different pore sizes ͑70 and 120 nm͒ and 250 nm interpore distances were used to investigate the effect of the interactions and of the diameter of the wires on their magnetic behavior. Nearly linear magnetization characteristics with small coercivity, observed for Fe nanowires, suggest the magnetization rotation to be the predominant magnetization process for the field applied transverse to the wires. The anisotropy of the arrays was governed by the shape anisotropy of the magnetic objects with different aspect ratios. Reduced interactions between the nanowires grown in Mi-Ha AAMs resulted in enhancement of the average anisotropy. It is believed that due to difference in spin configuration, the increased diameter of the nanowires led to reduction in the coercivity in the case of the field applied along the wires.

“…Arrays of nanoparticles with large aspect ratios can be produced by various methods, [1][2][3] but electron beam nanolithography seems to be the most flexible of all in defining the lateral structures. Arbitrary shapes with dimensions in the range from 30 nm to 100 m can be patterned using this method.…”

Section: Introductionmentioning

confidence: 99%

Microwave absorption of patterned arrays of nanosized magnetic stripes with different aspect ratios

Małkiński

Vovk

et al. 2007

Arrays consisting of nanosized stripes of Permalloy with different length-to-width ratios have been fabricated using electron beam nanolithography, magnetron sputtering, and lift-off process. These stripes have a thickness of 100 nm, a width of 300 nm, and different lengths ranging from 300 nm to 100 m. The stripes are separated by a distance of 1 m. Magnetization hysteresis loops were measured using a superconducting quantum interference device susceptometer. Microwave absorption at 9.8 GHz was determined by means of ferromagnetic resonance technique. The dependence of the resonant field on the angle between the nanostructure and the in-plane dc magnetic field indicates the presence of uniaxial magnetic anisotropy associated with the aspect ratio of the stripes. A maximum change of the resonant field of 1600 Oe was observed in the longest stripes, yet it was only 200 Oe for square shaped stripes. The linewidth of the resonant curve varied with the angle, in the range from 120 to 300 Oe. Most of the ferromagnetic resonance spectra exhibited multiple resonant peaks due to dimensional confinement of spin waves in the nanosized stripes. The maximum squareness of the magnetization hysteresis loop was for the field applied along the stripes, but the coercivity did not have a monotonic angular dependence as expected from the Stoner-Wohlfarth model for coherent magnetization rotation of the systems with uniaxial anisotropy.