Magnetic Anisotropy of a Single Cobalt Nanocluster
TL;DR: Three-dimensional switching field measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix are reported, able to separate the different magnetic anisotropy contributions and evidence the dominating role of the cluster surface.
Abstract: Using a new micro-SQUID setup, we investigate magnetic anisotropy in a single 1000-atom cobalt cluster. This system opens new fields in the characterization and understanding of the origin of magnetic anisotropy in such nanoparticles. For this purpose, we report three-dimensional switching field measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix. We are able to separate the different magnetic anisotropy contributions and evidence the dominating role of the cluster surface.
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TL;DR: Biocompatible magnetic nanosensors that act as magnetic relaxation switches (MRS) to detect molecular interactions in the reversible self-assembly of disperse magnetic particles into stable nanoassemblies are developed.
Abstract: Highly sensitive, efficient, and high-throughput biosensors are required for genomic and proteomic data acquisition in complex biological samples and potentially for in vivo applications. To facilitate these studies, we have developed biocompatible magnetic nanosensors that act as magnetic relaxation switches (MRS) to detect molecular interactions in the reversible self-assembly of disperse magnetic particles into stable nanoassemblies. Using four different types of molecular interactions (DNA-DNA, protein-protein, protein-small molecule, and enzyme reactions) as model systems, we show that the MRS technology can be used to detect these interactions with high efficiency and sensitivity using magnetic relaxation measurements including magnetic resonance imaging (MRI). Furthermore, the magnetic changes are detectable in turbid media and in whole-cell lysates without protein purification. The developed magnetic nanosensors can be used in a variety of biological applications such as in homogeneous assays, as reagents in miniaturized microfluidic systems, as affinity ligands for rapid and high-throughput magnetic readouts of arrays, as probes for magnetic force microscopy, and potentially for in vivo imaging.
866 citations
TL;DR: The magnetic properties of nanoparticles which are directly related to their applications in biomedicine are discussed, mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.
Abstract: Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.
829 citations
814 citations
TL;DR: In this paper, the key methods for the preparation of magnetic nanoparticles are described systematically and the experimental data on their properties are analyzed and generalised, as well as the main theoretical views on the magnetism of nanoparticles were considered.
Abstract: The key methods for the preparation of magnetic nanoparticles are described systematically. The experimental data on their properties are analysed and generalised. The main theoretical views on the magnetism of nanoparticles are considered.
802 citations
TL;DR: The key methods used in atomistic spin models are presented, which are then applied to a range of magnetic problems, and the parallelization strategies used enable the routine simulation of extended systems with full atomistic resolution.
Abstract: Atomistic modelling of magnetic materials provides unprecedented detail about the underlying physical processes that govern their macroscopic properties, and allows the simulation of complex effects such as surface anisotropy, ultrafast laser-induced spin dynamics, exchange bias, and microstructural effects. Here we present the key methods used in atomistic spin models which are then applied to a range of magnetic problems. We detail the parallelization strategies used which enable the routine simulation of extended systems with full atomistic resolution.
623 citations