SmCo5 Nanoparticles Research Articles

Co-reduction synthesis of uniform ferromagnetic SmCo nanoparticles

Ferromagnetic SmCo nanoparticles with narrow size distribution (5–8nm) were successfully prepared by polyol co-reduction using non-toxic inorganic precursors (nitrates) instead of deadly poisonous organometallic precursors (acetylacetonate or carbonyl compounds). In the synthesis, Sm3+ and Co2+ can get electrons from acetaldehyde (CH3CHO) and then are reduced to Sm and Co. However, the standard electrode potential of Sm3+ is far lower than that of Co2+ so that Co2+ is reduced early and then grow up quickly. The additive of CH3COOH increases the concentration of H+ and decreases the stability of Sm3+, which results in the co-reduction of the Co2+ and Sm3+. So the SmCo nanoparticles are synthesized in-situ. The coercivity and magnetization of the nanoparticles were 1041Oe and 55emu/g, respectively.

Synthesis of single-crystal Sm-Co nanoparticles by cluster beam deposition

Single-crystal Sm-Co nanoparticles have been successfully produced by a cluster beam deposition technique. Particles have been deposited by DC magnetron sputtering using high Ar pressures on both single-crystal Si substrates and Au grids for the magnetic and structural/microstructural properties, respectively. Oxidation of the particles is prevented by using carbon buffer and cover layers. Nanoparticles have a uniform size distribution with an average size of 4.2, 6 and 7 nm at 1, 1.5 and 2 Torr of Ar pressure, respectively. At 1 Torr, the particles have the disordered 1:7 structure and a high coercivity of 19 kOe at 10 K. These particles show a superparamagnetic behavior with a blocking temperature of TB = 145 K. From this value of TB and the particle volume, the value of anisotropy constant K is estimated to be around 2.2 × 107 ergs/cc. Heat is introduced to the particles during their flight to the substrate to increase the particle size. Nanoparticles of SmCo5 with an average size of 15 nm and high room temperature coercivity have been produced. No change in magnetic and structural properties of the samples has been observed even after 10 months. Cluster beam deposition could play a key role for the production of rare earth nanoparticles for many applications.

Chemical synthesis of hard magnetic SmCo nanoparticles

We report a facile synthesis of ferromagnetic SmCo nanoparticles (NPs) via a controlled reduction of SmCo–O NPs. The SmCo–O NPs were prepared by co-precipitation of Co(II) and Sm(III) acetates with hexadecyl-trimethylammonium hydroxide and were embedded in a CaO matrix. The 7 nm SmCo3.6–O NPs were reduced by Ca at 960 °C and converted into ferromagnetic 6 nm SmCo5 NPs with their coercivities reaching 7.2 kOe. The synthesis provides a viable route to ferromagnetic SmCo NPs with controlled compositions and magnetism for high performance permanent magnetic applications.

Synthesis and assembly of magnetic nanoparticles for information and energy storage applications

This mini-review summarizes the recent advances in chemical synthesis and assembly of monodisperse magnetic nanoparticles for magnetic applications. After a brief introduction to nanomagnetism, the review focuses on recent developments in solution phase syntheses and assemblies of monodisperse Fe, CoFe, FePt and SmCo5 nanoparticles. The review further outlines the structural and magnetic properties of these nanoparticles for magnetic information and energy storage applications.

Effects of particle size and composition on coercivity of Sm–Co nanoparticles prepared by surfactant-assisted ball milling

The SmCox (x=3.5, 4, 5, 6, 8.5, and 10) magnetic nanoparticles with different composition have been prepared by surfactant-assisted ball milling technique. By controlling the settle-down time and the centrifugation conditions, the SmCox nanoparticles with different particle size and narrow size distribution were successfully obtained. It was observed that the SmCo nanoparticles become unstable with increasing Sm content. It was also observed that the coercivity of the SmCox nanoparticles increases with Co content and particle size, indicating a complex effect of the particle size and composition on magnetic hardening of the hard magnetic nanoparticles.

High-density gas aggregation nanoparticle gun applied to the production of SmCo clusters

We describe in this article the application of a high-density gas aggregation nanoparticle gun to the production and characterization of high anisotropy SmCo nanoparticles. We give a detailed description of the simple but efficient experimental apparatus with a focus on the microscopic processes of the gas aggregation technique. Using high values of gas flux (~45 sccm) we are able to operate in regimes of high collimation of material. In this regime, as we explain in terms of a phenomenological model, the power applied to the sputtering target becomes the main variable to change the size of the clusters. Also presented are the morphological, structural, and magnetic characterizations of SmCo nanoparticles produced using 10 and 50 W of sputtering power. These values resulted in mean sizes of ~12 and ~20 nm. Significant differences are seen in the structural and magnetic properties of the samples with the 50 W sample showing a largely enhanced crystalline structure and magnetic anisotropy.

Fabrication of SmCo5 Alloy Magnetic Nanoparticles by Assistance of Copper and Their Magnetic Properties

Abstract SmCo5 magnetic nanoparticles were preparaed through a simultaneous reduction of Sm(acac)3·xH2O and Co(acac)3 by assistance of Cu(acac)2 and NaBH4 in the presence of oleic acid and oleylamine as a protectant. Supplementation of Cu activated the formation of SmCo5 nanoparticles having a CaCu5 structure, and use of NaBH4 as a reducing agent played an important role to prevent samarium and cobalt from oxidation during preparation. The mean particle diameter was 3.4 nm, having a well-controlled crystal morphology. The magnetic properties of the prepared nanoparticles represented sufficiently high coercivity and magnetization of 1300 Oe and 15.7 emu g−1, respectively, at room temperature.

Anisotropic Sm-(Co,Fe) nanoparticles by surfactant-assisted ball milling

Magnetically hard Sm2(Co0.8Fe0.2)17 and SmCo5 nanoparticles have been produced by using surfactant-assisted low- and high-energy ball milling techniques. Surfactants prevent the rewelding of the crashed particles during the milling process. Heptane was used as the milling medium and oleic acid as the surfactant. High-energy ball milling experiments took place in a milling vial with carbon steel balls by using an SPEX 8000M high-energy ball milling machine. The coercivity was found to increase with milling time with values of 2.3 kOe for Sm2(Co0.8Fe0.2)17 and 18.6 kOe for SmCo5 after 4 h of milling. Transmission electron microscopy data showed that the milled powders consisted of nanoparticles with an average size of 5–6 nm and a narrow size distribution. Samples deposited on copper coated carbon grid showed self-assembled nanoparticles which could be further aligned when subjected to a magnetic field.

Magnetic nanoparticles: synthesis, functionalization, and applications in bioimaging and magnetic energy storage

This tutorial review summarizes the recent advances in the chemical synthesis and potential applications of monodisperse magnetic nanoparticles. After a brief introduction to nanomagnetism, the review focuses on recent developments in solution phase syntheses of monodisperse MFe(2)O(4), Co, Fe, CoFe, FePt and SmCo(5) nanoparticles. The review further outlines the surface, structural, and magnetic properties of these nanoparticles for biomedicine and magnetic energy storage applications.

Magnetic Property of Sm-Co Nanoparticles Prepared by Solution Phase Metal Salt Reduction

Sm-Co magnetic nanoparticles were successfully synthesized at high temperature above 680 degrees C in solution phase. The chemical composition was determined by EDX and it was found that the composition of as-synthesized Sm-Co magnetic nanoparticles showed less Sm content compared with the composition of starting materials. From TEM and FE-SEM measurements, the morphology of as-synthesized and heat-treated Sm-Co a magnetic nanoparticle was confirmed as hexagon and apatite crystal structure. Curie temperature was observed at around 680 degrees C correspond to SmCo5 phase. The magnetic property was measured by VSM and shows the ferromagnetic characteristics.

Capped Bimetallic and Trimetallic Nanoparticles for Catalysis and Information Technology

AbstractSummary: Polymer‐capped metal nanoparticles can be recognized as a kind of macromolecule‐metal nanoparticle complexes. Here the preparations of the capped bimetallic and trimetallic nanoparticles, in which each particle contains two and three elements of metal, respectively, are presented. They may have a random alloy, a core/shell, or other kinds of structure depending on the preparation method and the combination of elements. The core/shell structure is advantageous to electronically control the activity of metal catalysts. The triple core/shell structured trimetallic nanoparticles were found to have higher catalytic activity than the corresponding monometallic and bimetallic nanoparticles in three cases. Capped metal nanoparticles were also used as a dopant to liquid crystals. Liquid crystal displays, fabricated by metal nanoparticle‐doped liquid crystals, showed faster response than those without dopants. Bimetalization could increase the long‐term stability in the doped liquid crystal displays. Thus, metal nanoparticles can improve the electronic display system, which occupies an important position in information technology. In addition, SmCo5 nanomagnets were successfully prepared by a chemical method, possibly providing a new building block for information technology. The prepared SmCo5 nanoparticles have a coercivity of 1500 Oe at room temperature. The bimetallic nanoparticles may open a new field in super‐high‐density magnetic memories.

Direct chemical synthesis of high coercivity air-stable SmCo nanoblades

Ferromagnetic air-stable SmCo nanoparticles have been produced directly using a one-step chemical synthesis method. X-ray diffraction studies confirmed the formation of hexagonal SmCo5 as a dominant phase. High resolution transmission electron microscopy confirms the presence of uniform, anisotropic bladelike nanoparticles approximately 10nm in width and 100nm in length. Values of the intrinsic coercivity and the magnetization in the as-synthesized particles are 6.1kOe and 40emu∕g at room temperature and 8.5kOe and 44emu∕g at 10K, respectively. This direct synthesis process is environmentally friendly and is readily scalable to large volume synthesis to meet the needs for the myriad of advanced permanent magnet applications.

Iron Oxide Shell as the Oxidation-Resistant Layer in SmCo5@Fe2O3 Core–Shell Magnetic Nanoparticles

This paper presents a synthesis of magnetic nanoparticles of samarium cobalt alloys and the use of iron oxide as a coating layer to prevent the rapid oxidation of as-made Sm-Co nanoparticles. The colloidal nanoparticles of Sm-Co alloys were made in octyl ether using samarium acetylacetonate and dicobalt octacarbonyl as precursors in a mixture of 1,2-hexadecanediol, oleic acid, and trioctylphosphine oxide (TOPO). Such Sm-Co nanoparticle could be readily oxidized by air and formed a CoO antiferromagnetic layer. Exchange biasing was observed for the surface oxidized nanoparticles. In situ thermal decomposition of iron pentacarbonyl was used to create iron oxide shells on the Sm-Co nanoparticles. The iron oxide shell could prevent Sm-Co nanoparticles from rapid oxidation upon the exposure to air at ambient conditions.

Magnetic nanoparticles produced by surfactant-assisted ball milling

Nanoparticles of Fe, Co, FeCo, SmCo, and NdFeB systems with sizes smaller than 30nm and narrow size distribution have been successfully prepared by ball milling in the presence of surfactants and organic carrier liquid. It has been observed that the nanoparticles prepared by milling Fe and FeCo powders were close to spherical in their shapes, whereas those of Co, SmCo, and Nd–Fe–B showed elongated rod shapes. The nanoparticles showed superparamagnetic behavior at room temperature, except for the SmCo nanoparticles that were ferromagnetic. Nanoparticles of all types showed ferromagnetic behavior at low temperatures. The compositions of nanoparticles prepared by milling the SmCo, NdFeB, and FeCo powders were found to be deviated from the starting powders.

Synthesis of Magnetic Nanoparticles by Sputtering

AbstractThe influence of experimental condition on morphology of FePt and Sm-Co nanoparticles synthesized by sputtering in a relatively high gas pressure has been studied. The sputtering apparatus is equipped with an annealing furnace that enables pre-deposition annealing of the nanoparticles. The effect of the annealing temperature on the ordering to the L10 FePt nanoparticles was also investigated. The morphology of the particles depends on a gas pressure and gas flow rate, but the sensitivity to experimental condition differs between FePt and Sm-Co. The morphology and domain structure of FePt nanoparticle are relatively the same in a wide range of experimental condition, whereas those of Sm-Co nanoparticle are significantly changed by variation of a gas pressure. FePt nanoparticles annealed in the annealing furnace prior to their deposition onto the substrate have the ordered L10 phase, which has an advantage for producing a magnetic recording media.

Chemical synthesis of narrowly dispersed SmCo5 nanoparticles

In this article we report a chemical synthetic means for generating a high Ku magnetic material—narrowly dispersed nanoparticles of SmCo5. Using Co2(CO)8 and Sm(acac)3 as the precursors under air-free conditions, we produced SmCo5 nanoparticles according to the procedure reported by Sun et al. [Science 287, 1981 (2000)] but with some modifications. The nanoparticles, with diameters of 6–8 nm, have a SmCo5 composition, as indicated by transmission electron microscopy, electron diffraction, and x-ray photoelectron spectroscopy. The magnetization measurement of the nanoparticles, exhibits superparamagnetism, which is blocked for temperatures below ∼110 K, suggesting Ku to be ∼2.1×106 erg/cm3 for the as-prepared particles.

Annealing effects on the coercivity of SmCo5 nanoparticles

The enhanced coercivity of ball milled nanoparticles of SmCo5 has been attributed to the reduced particle size, but the milling process introduces additional strain which can also affect the coercivity. Here the effects of size and strain are decoupled from each other using a combination of x-ray diffraction, electron microscopy, and coercivity measurements. Ball milled SmCo5 nanoparticles were annealed under different temperature, time, and atmospheric conditions to minimize the strain without chemically altering the sample, and with minimal grain growth and sintering. X-ray diffraction was used to determine if phase changes had occurred, and to monitor the average grain size and strain. From scanning electron microscopy the log-normal size distributions were found and no evidence of sintering was revealed. The sample coercivities were measured by superconducting quantum interference device following annealing.

Hard Magnetic Nanoparticles and Nanocomposites

ABSTRACTMany high performance permanent magnets are nanostructured materials. The magnetic properties of nanoparticles are discussed in terms of characteristic length scales, including the maximum monodomain size and the exchange length. Experimental results for ball milled SmCo5 nanoparticles are presented, showing deviations from idealized behavior. Because of the short exchange length, this can be understood in terms of independent nucleation of reverse domains in grains within larger particles. With a much longer exchange length, FeCo alloy nanoparticles show reduced coercivity in a high density compact, in accordance with the random anisotropy model. The SmCo5 and FeCo nanoparticles were mixed and compacted in an attempt to make an exchange spring nanocomposite. However, significant exchange between the hard and soft phases was not observed because the sample density was too low. Processing considerations for improved co-compaction of these nanoparticles are discussed.