Highly L10-ordered FePt thin films with a strong (001) texture were successfully fabricated on amorphous substrates simply by co-sputtering and rapid thermal annealing at a low temperature of 400 °C. ...The morphology of FePt thin films depended strongly on the heating rate, changing from a continuous structure with an atomically flat surface to an island-like structure. The change of the morphology resulted in a drastic increase of coercivity, indicating that the magnetization process could be controlled by the heating condition. This fabrication method of ordered FePt thin films is favorable in view of the compatibility for a practical device fabrication process.
We studied the structure and magnetic properties of co-sputtered Co
1−
x
C
x
thin films using a transmission electron microscope (TEM) and a SQUID magnetometer. These properties were found to depend ...critically on deposition temperature,
T
S, and composition,
x. Generally, phase separation into metallic Co and graphite-like carbon phases proceeds with increasing
T
S and decreasing
x. Plan view and cross-sectional TEM images of the films prepared showed that Co grains about 10–20
nm in diameter and 30–50
nm in height are three-dimensionally separated by graphite-like carbon layers 1–2
nm thick. Optimum magnetic properties with saturation magnetization of 380
emu/cc and coercivity of 400
Oe were obtained for a film with
x=0.5 and
T
S=350°C.
We have investigated the structures of the
θ′ and T
1 precipitates in Al–1.6wt%Li–3.2wt%Cu and Al–2.4wt%Li–3.2wt%Cu alloys aged at 220 °C. The
θ′ precipitates in the 1.6 wt%-Li alloy are those known ...for the Al–Cu binary system (
a=0.40 and
c=0.58 nm); whereas those in the 2.4 wt%-Li alloy exhibited two atypical structures. One, named a type I T
B′ plate in this study, is isostructural to the known
θ phase with a large
c value of about 0.64 nm, having a habit plane parallel to the matrix {1 0 0}
α
; the other, type II T
B′, is characterized by
a=0.41 and
c=0.61 nm, having a habit plane inclined at about 20° with {1 0 0}
α
, while maintaining a coherent interface. Also images of {1 1 1} precipitates in the 1.6 wt%-Li alloy revealed a continuous change from the T
1 phase (
c=0.935 nm), to a structure with
c=0.87–0.90 nm. The image and small lattice parameter suggest that this {1 1 1} precipitate is likely to be the Ω phase.
The Double Chooz experiment has determined the value of the neutrino oscillation parameter θ13 from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses ...a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds sin22θ13=0.097±0.034 (stat.)±0.034 (syst.), excluding the no-oscillation hypothesis at 2.0σ. This result is consistent with previous measurements of sin22θ13.
Fracture behavior of pure niobium (Nb) by several hydrogenation procedures has been investigated to elucidate the fundamental mechanisms of hydrogen pulverization, which can then be used to produce ...fine Nb powders with high purity. Concentric, cracks and microcracks were introduced in recrystallized Nb specimens, leading to pulverization, when they absorb hydrogen enough to form a large volume of the face-centered orthorhombic. beta-NbH phase. This hydride phase exhibits anisotropic expansion of Nb lattice and embrittlement. Thus, the fracture of Nb plates occurs in the following sequence: hydrogen absorption, the formation of the ordered, hydride phase, strain generation arising from the phase transformation, and crack nucleation and propagation. The authors also show that Nb powders less than 1 mm were prepared by hydrogenation and ball-milling at a temperature below 203 K, in which hydrogen was removed by dehydrogenation at above 724, K. Thus, fine and contamination-free Nb powders can be effectively, fabricated by using hydrogenation, ball-milling, and dehydrogenation procedures.
It is well known that structural relaxation in a bulk metallic glass affects some properties such as viscosity, electrical conductivity, and ductility. The free volume in glassy alloy, which is open ...volume retained by rapidly solidification from liquid state, has a significant roll for those properties. In order to discuss the nature of free volume in a Zr50Cu40Al10 bulk metallic glass, positron lifetime measurements have been performed for this metallic glass before and after annealing, and all positron lifetime spectra have been decomposed into multi components as a size distribution function by use of CONTIN-PALS II program. The positron lifetime distribution for this metallic glass has a broad spectrum comparing to crystal metal including a single vacancy, and its average lifetime corresponds to the free volume size. This width of positron lifetime (free volume size) distribution decreases by the annealing at 673 K. This change of the positron lifetime distribution can be attributed to a free volume relaxation.
Structural changes of cyclically hydrogenated TiMn2 based alloys, in which the compositions of the TiMn2 Laves phase are about 60 and 61 at.% Mn, have been investigated to understand the mechanism of ...the degradation of their hydrogen absorbing capacity. There are no apparent changes in micro- and nano-scale metallurgical features in the Ti-60at.% Mn alloy, which exhibited superior endurance cyclic property. On the contrary, hydride formation, decrease in crystalline size and/or introduction of heterogeneous strain, and the deviation of Mn atom position have been observed in Ti-61 at.% Mn alloy, which exhibited poor cycle property, arising from retained hydrogen in the TiMn2 Laves phase. Therefore, it is considered that structural changes with cyclic hydrogenation sensitively depend on the composition of TiMn2 Laves phase, governing the degradation behavior. The mechanism of the degradation of cyclic property is discussed in view of the substitution behavior in the hexagonal TiMn2 Laves phase.
We study the enhanced spin relaxation time of Au nanoparticles in nanopillar-shaped double-barrier junction devices with a stacked Fe/MgO/Au-nanoparticle/MgO/Fe structure. The size of Au ...nanoparticles located in a current path is deduced from a transmission electron micrograph and the Coulomb blockade behavior in the current-voltage characteristics of the devices. A finite tunnel magnetoresistance (TMR) is observed above a critical current and is attributable to spin accumulation in Au nanoparticles. Based on a simple model of TMR due to spin accumulation in a nanoparticle, the spin relaxation time tau sub()sis estimated from the magnitude of the critical current. The temperature and bias-voltage region where TMR appears are determined from systematic observations, showing that the appearance of TMR is not associated with the Coulomb blockade but with spin accumulation. We find that the obtained tau sub()sis anomalously extended (~800 ns) at low temperatures and abruptly decreases above a critical temperature. Interestingly, the critical temperature strongly depends on the size of the Au nanoparticles and is much lower than the effective temperature corresponding to the discrete energy spacing. A theoretical analysis for the spin relaxation of electrons with discrete energy levels shows that not only the anomalously extended spin relaxation time, but also the strong temperature dependence of tau sub()sarise from the broadening of discrete energy levels due to coupling with phonons in the surrounding matrix. Numerical calculations using reasonable parameter values well reproduce the observed temperature and size dependence of the spin relaxation time in Au nanoparticles.
The effect of bait-delivered anthelmintic to reduce the prevalence of Echinococcus multilocularis in wild red foxes was evaluated in Koshimizu, in the eastern part of Hokkaido, Japan. The study area ...(200 km2) was divided into baited and non-baited sections. The anthelmintic baits were distributed around fox den sites in the baited section every month for 13 months. After 1 year of the anthelmintic bait distribution, the prevalence of E. multilocularis in foxes, evaluated either by the parasite egg examination (from 27.1 to 5.6%) or coproantigen ELISA (from 59.6 to 29.7%), decreased in the baited section contrasting to that in the non-baited section (parasite egg: from 18.8 to 24.2%; ELISA: from 41.9 to 45.8%). The prevalence of E. multilocularis in grey red-backed vole Clethrionomys rufocanus, caught around fox dens, born after bait distribution also decreased and was significantly lower than that in non-baited section. However, within the study periods, the coproantigen-positive rate in fox faeces sporadically increased, while egg-positive rate constantly decreased. Since coproantigen ELISA can detect pre-patent infection, this observation indicates that reinfection pressure in the baited section was still high even after the 13 months of anthelmintic bait distribution. Therefore, the bait distribution longer than our study period is required for the efficient control of E. multilocularis in wild red fox population.
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