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Herein, we achieved a large reversible room temperature magneto-caloric effect (MCE) through synergic tuning of martensitic transformation (MT) temperatures and transition entropy change (ΔStr) via micro-alloying with transition metals (Ti, V, and Cr) in Ni45Co5Mn40Sn10 meta-magnetic Heusler alloys (MHAs). By the minor addition of TM, MT temperatures were brought down to below room temperature and ΔStr was reduced while maintaining narrow MT temperature range (ΔT) and large difference in magnetization (ΔM) of Ni45Co5Mn40Sn10 MHA. In particular, Ni43.8Cr1.2Co5Mn40Sn10 MHA exhibited a very large reversible room temperature magnetic entropy change (ΔSM) of 24.5 J/kg.K with a broad operating temperature window of ~11K at 5 T. Indeed, the MHA exhibited a very effective refrigeration capacity (RCeff) of 276 J/kg for 5 T, which is the largest value among the reported Ni-Mn-based MHAs. The decrease of ΔStr reduces the magnetic field required for completely reversible MT and accelerates the saturation of ΔSM, which leads to maximum RCeff value in the composition of MHA. Thus, we can conclude that smaller ΔStr with narrow ΔT and large ΔM is a key variable to develop MHA with reversible MCE under low magnetic field, which will ultimately give us a guideline for the tailor-made design of highperformance magneto-caloric materials. [ABSTRACT FROM AUTHOR]

We propose a crawling and drilling microrobot actuated by an external precessional magnetic field (EPMF) to effectively unclog obstructed blood vessels. Conventional crawling microrobots can only generate crawling motions using an external oscillating magnetic field. The proposed microrobot can generate navigating (crawling) and drilling motions selectively or simultaneously by controlling the EPMFs. We prototyped the proposed microrobot, and conducted several experiments to verify the efficacy of the crawling and drilling ability of the microrobot in a tubular environment. [ABSTRACT FROM AUTHOR]

It has been possible to produce and characterize submicron-size tunneling junctions using c-axis YBa2Cu3O(sub 7-y) thin films. It was found that the stack number and area of the intrinsic Josephson junctions could be easily controlled by scanning and etching the ion beam.

We investigated current-voltage characteristics (IVCs) of intrinsic Josephson junctions (IJJs) for c-axis oriented La[SUB1.85]Sr[SUB0.15]CuO[SUB4] thin films. We fabricated IJJs with two kinds of structures. One was a mesa structure with a junction area of 22- 194 μm[SUP2] fabricated by using conventional photolithography and Ar-ion milling, and the other was a microbridge structure with a junction area of 1.1- 3.6 μm[SUP2] fabricated by using a focused-ion-beam technique. The mesa-type IJJs exhibited resistively-shunted-junction-like IVCs with no hysteresis. The temperature dependence of their critical current followed the Ambegaokar-Baratoff relation. IVCs of the microbridge-type IJJs, on the other hand, exhibited voltage jump and clear hysteresis. The different behaviors between the mesa-type and the microbridge-type IJJs were explained by the different numbers of grain boundaries involved in the IJJs. [ABSTRACT FROM AUTHOR]

Ni[sub 80]Fe[sub 20]-Mn alloy thin films were fabricated using magnetron sputtering in order to study the microstructural changes that develop in an exchange couple (Ni[sub 80]Fe[sub 20] and Mn). In the process, we discovered that the alloy films phase separated into Ni[sub 80]Fe[sub 20] and Mn when annealed at 400 °C, although bulk Ni[sub 80]Fe[sub 20] and Mn are miscible at room temperature. Moreover, a strong crystallographic texture developed during annealing, especially for films with high Mn content. The increase of texture was attributed to the volume expansion taking place in the phase separation. It was speculated that the as-deposited alloy films had a large coherent interfacial strain, possibly due to inhomogeneous alloying. In turn, this hindered the formation of intermetallic compounds, and instead forced a phase separation to reduce the interfacial energy. [ABSTRACT FROM AUTHOR]

Pinned electrodes of the magnetic tunnel junction (MTJ) consisting of Ta/AlO[SUBx]/ CoFe(x)/IrMn/NiFe/Ta, where 35 &Aring

An original study of longitudinal photoconductivity (PC) of undoped GaAs/AlGaAs V-grooved quantum wires (QWRs) is carried out by measuring the PC along the wire direction. The results can be helpful in the fabrication of nanodevices utilizing longitudinal phototransport in GaAs QWRs.

Presents a study which investigated the influence of electric field on the excitation states in Al[0.4]Ga[0.6]As and gallium arsenide asymmetric coupled quantum wells grown by molecular-beam epitaxy through photoluminescence measurements. Effect of electric fields on quantum wells; Equation of the effective mass Hamiltonian for the electron and hole; Materials and methods used; Calculation of the theoretical energy levels and wave functions.

Electronic structures of FeCr2X4 (X=S and Se) have been investigated by employing soft-x-ray absorption spectroscopy and soft-x-ray magnetic circular dichroism (XMCD). It is found that FeCr2S4 and FeCr2Se4 have similar electronic structures. The valence states of Cr and Fe ions are nearly trivalent (Cr3+) and divalent (Fe2+), respectively. The Fe 3d states are strongly hybridized to the X p states. The Fe and Cr 2p XMCD study provides evidence for the antiparallel alignment between Cr and Fe spins and the strong hybridization between the Fe 3d and X p electrons. [ABSTRACT FROM AUTHOR]

Nanoparticles of Fe[SUB2]O[SUB3] with a mean particle size of 4-50 nm have been prepared by the pulsed wire evaporation method, and its structural and magnetic properties were studied. From the main peak intensity of x-ray diffraction the amount of Γ-Fe[SUB2]O[SUB3] and α-Fe[SUB2]O[SUB3] in sample is composed about 70% and 30%, respectively. The coercivity (53 Oe) and the saturation magnetization (14 emu/g) are about 20% of those of the bulk Gamma;-Fe[SUB2]O[SUB3]. A quadrupole line on the center of Mössbauer spectrum represents the superparamagnetic phase of Γ-Fe[SUB2]O[SUB3] with a mean particle size of 7 nm or below. [ABSTRACT FROM AUTHOR]

Two-stacked intrinsic Josephson junctions (IJJs) on a Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8 + δ](Bi-2212) whisker with a submicron hole are micromachined by a 3D focused ion beam (FIB) etching method. The junction area, the number of elementary junctions, and the loop area of the SQUIDs are 3, 20, and 0.42 µm², respectively. The SQUIDs show typical I-V characteristics of IJJs with a critical current I[sub c] of 12 µA at 4.2 K. The modulation parameter Β[sub L]( = 2I[sub C]L / Φ[sub 0]) is 6.4, and the inductance L of the SQUID is ll20pH. That includes the inductances of the elementary junction around a SQUID loop. In a strong magnetic field, the Fraunhofer pattern is obtained and well fitted to the calculated value from the junction size, ΔB = Φ[sub 0] / tW; t is the interlayer distance, and W is the junction width. In a low magnetic field, approximately 10% of the I[sub C] modulation corresponding to the value of β[sub L] is observed. Eighty G of the modulation period approximately agrees with the value calculated from the SQUID. [ABSTRACT FROM AUTHOR]

We report successful fabrication and characteristics of submicron-size tunneling junctions using c-axis YBa[sub 2]Cu[sub 3]O[sub 7-y] (YBCO) thin films of 800 nm thickness and Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+δ](Bi-2212) single-crystal whiskers. The junctions were made using a three-dimensional focused-ion-beam etching method. First, a microbridge was patterned in a required junction width by normal direction etching. By tilting the sample stage up to 90°, two grooves on the bridge were etched from the lateral direction in order to create the required junction size. The 60 K YBCO junctions did not show any degradation of critical current density (J[sub c]) down to an in-plane area of 0.5 μm2 and showed current-voltage (I-V) characteristics of the collective switching transition from the zero voltage state to the resistive state. For Bi-2212 stacks smaller than 1 μm2, we identified some of the features of charging effects on the I-V characteristics. &! copy; 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Effect of grain size on magnetoresistance (MR) and electrical and magnetic properties of double perovskite Ba[sub 2]FeMoO[sub 6] (BFMO) have been investigated. BFMO samples with different grain size have been prepared by the conventional solid state reaction followed by sintering in a stream of 5% H[sub 2]/Ar at 1100 °C with various sintering times. The size of grain increases with increasing of sintering time. Temperature dependent magnetization is the same for samples with different grain size. However, electrical resistivity ρ(T) and MR are affected by the grain size; the ρ(T) and the MR value decrease with an increase in grain size. In spite of the different grain size, the ρ(T) shows a metallic behavior below the ferromagnetic transition temperature. Low magnetic field applied to the sample considerably reduces the resistivity over the whole temperature. The magnitude of MR for the sample sintered for 5 h is as large as 31% and 7% with the magnetic ! field of 0.7 T at 12 and 300 K, respectively. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses the reduction of stress-induced leakage currents (SILC) in thin oxides by application of a low post-stress gate bias. Correlation between the reduction of SILC and the applied gate bias; Enhancement of the reduction of SILC in a hydrogen ambient; Link between the SILC reduction and trapped-hole annealing.

Presents a study which investigated the effect of the thermal spike mechanism for ion mixing of tracers in silver. Factors that promote thermal spike diffusion; Selection of tracer elements; Comparison of the thermal diffusion coefficients and tracer ion mixing efficiencies.