Fabrication of oriented L1₀-FePt and FePd nanoparticles with large coercivity

Oriented L1 0-FePt and FePd nanoparticles with coercivities as large as 5 kOe (FePt) and 3 kOe (FePd) were fabricated by alternating deposition of Pt(or Pd) and Fe nanoparticles and their annealing at the temperatures between 773 and 873 K on single crystal NaCl and MgO. Atomic ordering reactions and degrees of order towards the L1 0-structure formation in these nanoparticles were investigated by high resolution electron microscopy and electron diffraction, and magnetic coercivities at low temperature were also measured. The long range order parameter of the FePt nanoparticles was ∼0.56 even after annealing at 873 K for 24 h. The coercivity of the FePt nanoparticles at 100 K was as high as twice the room temperature value. The low degree of order in the L1 0-structure formation and the thermal effect on magnetization have been found in the present FePt and FePd nanoparticles. These are closely concerned with the origin of the coercivity values which are very small in comparison with those expected from the single magnetic domain theory. © 2002 American Institute of Physics.Kazuhisa Sato, Bo Bian, and Yoshihiko Hirotsu, "Fabrication of oriented L10-FePt and FePd nanoparticles with large coercivity", Journal of Applied Physics 91, 8516-8518 (2002) https://doi.org/10.1063/1.1456446

Atomic ordering reation and associated variation of magnetic coercivity of oriented L1₀-Fept nanoparticles

Atomically ordered FePt nanoparticles (L10-type structure) covered with amorphous (a-) Al2O3 have been fabricated. In this process, Fe particles were deposited on Pt “seed” particles which were epitaxially grown on (100) NaCl or MgO substrates. Annealing the a-Al2O3/Fe/Pt films at temperatures higher than 773 K leads to a formation of ordered nanoparticles with mutual fixed orientation in a monolayer form. Three variant ordered domains of the tetragonal L10 structure coexisted in a single nm-sized FePt particle, even in a particle as small as 7 nm. According to in-situ electron diffraction study, the degree of order of the ordered structure started to increase on annealing at 773 K and almost saturated on annealing at 873 K for 16 h. The magnetic coercivity varied depending on the particle size and the degree of order in the L10 structure formation. The perpendicular coercivity exceeded the in-plane one during the annealing. The in-plane coercivities of FePt nanoparticles measured both parallel to [100]MgO and [010]MgO directions were almost equal in numerical value. These results reflect the ordered domain formation process and the volume fraction of the domains. Remanent magnetization decay measured for the in-plane magnetization revealed a magnetic relaxation with the type of magnetic dipolar interaction between the FePt particles

Studies on the fungal diseases in crustaceans. I. Lagenidum scyllae sp. nov. isolated from cultivated ova and larvae of the mangrove crab (Scylla serrata)

Lagenidium scyllae , a marine mastigomycete from the ova and larvae of the mangrove crab, is described and illustrated as new. The fungus grew at a temperature range of 16-42 C, with an optimum at 22.5-31.8 C. It grew well in peptone-yeast-glucose (PYG) broth containing 2-3% NaCl. In PYG-sea water medium, it grew at a pH range of 5-11

Ordering of island-like FePt crystallites with orientations

Thin films of oriented island-like crystallites of L10 FePt separated by amorphous (a-) Al₂O₃ were fabricated. The process took advantage of the overgrowth of α-Fe on Pt "seed" particles epitaxially grown on (100) NaCl and MgO substrates and the ordering reaction between Fe and Pt upon annealing at temperatures higher than 500°C. The coercivities of the annealed (600°C for 6 h) a-Al₂O₃/Fe(1 nm)/Pt (1.5 nm) films on both the NaCl (100) and MgO (100) substrates are higher than 3.3 kOe. Transmission electron microscopy observation showed that the film consisted of oriented L10 FePt island-like crystals with an average size of 12 nm and a separation of 4 nm. It was found that any one of the three 〈100〉 axes of the fcc Pt parent particles could act as the tetragonal c axis of the L10 FePt superstructure and all three-variant ordered crystalline domains of the tetragonal L10 phase could exist in the small 10-nm-size FePt crystallites. The high magnetic coercivity of the film, with well-separated FePt particles, can be attributed to the ordering (L10) as well as the oriented nature of the FePt crystallites. © 1999 American Institute of Physics.Bo Bian, Kazuhisa Sato, and Yoshihiko Hirotsu, "Ordering of island-like FePt crystallites with orientations", Appl. Phys. Lett. 75, 3686-3688 (1999) https://doi.org/10.1063/1.125429

Body-Area Capacitive or Electric Field Sensing for Human Activity Recognition and Human-Computer Interaction: A Comprehensive Survey

Due to the fact that roughly sixty percent of the human body is essentially composed of water, the human body is inherently a conductive object, being able to, firstly, form an inherent electric field from the body to the surroundings and secondly, deform the distribution of an existing electric field near the body. Body-area capacitive sensing, also called body-area electric field sensing, is becoming a promising alternative for wearable devices to accomplish certain tasks in human activity recognition and human-computer interaction. Over the last decade, researchers have explored plentiful novel sensing systems backed by the body-area electric field. On the other hand, despite the pervasive exploration of the body-area electric field, a comprehensive survey does not exist for an enlightening guideline. Moreover, the various hardware implementations, applied algorithms, and targeted applications result in a challenging task to achieve a systematic overview of the subject. This paper aims to fill in the gap by comprehensively summarizing the existing works on body-area capacitive sensing so that researchers can have a better view of the current exploration status. To this end, we first sorted the explorations into three domains according to the involved body forms: body-part electric field, whole-body electric field, and body-to-body electric field, and enumerated the state-of-art works in the domains with a detailed survey of the backed sensing tricks and targeted applications. We then summarized the three types of sensing frontends in circuit design, which is the most critical part in body-area capacitive sensing, and analyzed the data processing pipeline categorized into three kinds of approaches. Finally, we described the challenges and outlooks of body-area electric sensing

Searching for cosmic string induced stochastic gravitational wave background with the Parkes Pulsar Timing Array

We search for stochastic gravitational wave background emitted from cosmic strings using the Parkes Pulsar Timing Array data over 15 years. While we find that the common power-law excess revealed by several pulsar timing array experiments might be accounted for by the gravitational wave background from cosmic strings, the lack of the characteristic Hellings-Downs correlation cannot establish its physical origin yet. The constraints on the cosmic string model parameters are thus derived with conservative assumption that the common power-law excess is due to unknown background. Two representative cosmic string models with different loop distribution functions are considered. We obtain constraints on the dimensionless string tension parameter $G\mu<10^{-11}\sim10^{-10}$, which is more stringent by two orders of magnitude than that obtained by the high-frequency LIGO-Virgo experiment for one model, and less stringent for the other. The results provide the chance to test the Grand unified theories, with the spontaneous symmetry breaking scale of $U(1)$ being two-to-three orders of magnitude below $10^{16}$ GeV. The pulsar timing array experiments are thus quite complementary to the LIGO-Virgo experiment in probing the cosmic strings and the underlying beyond standard model physics in the early Universe.Comment: 10 pages, 8 figures, 4 tables. Comments welcom