Search

NiFe/FeMn/NiFe trilayer structure forms an integral part of many conventional and tunneling magnetoresistance spin valve structures with FeMn antiferromagnetic layer. A systematic investigation of the exchange bias variations of the seed and top pinned NiFe layers in the NiFe/FeMn/NiFe trilayer structure is reported as a function of thickness of all the three constituting layers, in multilayers prepared by rf magnetron sputtering. X-ray diffraction patterns show the (111) texture for the NiFe and FeMn layers, necessary for the development of antiferromagnetic γ-fcc phase. In thickness variation studies of all the three magnetic layers, seed NiFe layer shows greater bias (150 Oe) than the top pinned NiFe layer (80 Oe only). The exchange bias shows the expected 1/t behavior for increasing NiFe layer thickness after initial maxima at low thickness. In the FeMn antiferromagnet layer thickness variation on the other hand, the large bias values attained around 5 nm thickness is nearly retained up to a thickness of 25 nm and the bias for the top NiFe layer is again substantially lower. The greater bias observed for the seed NiFe layer in all the three thickness variation studies is attributed to its growth over a saturated (111) oriented NiFe seed layer, which induces formation of interfacial FeMn layers with a net parallel spin ordering, in presence of the constant applied field. On the other hand, at the top FeMn/NiFe surface, the rigid FeMn surface with compensated bulk spin ordering formed already, is not easily biased and reoriented along the top NiFe layer, to develop as much parallel net spins in the antiferromagnetic material, and hence lower bias. [ABSTRACT FROM AUTHOR]

Presents the optimized planar Hall resistance (PHR) obtained by using biaxial currents in a NiO/NiFe bilayer. Optimization of biaxial currents; Advantages of the PHR in the optimized currents; Anisotropic magnetoresistance.

Presents the results of a comparative study of the solid-state reaction in a series of Ti/Ni multilayered films (MLF) with a bilayer period of 0.65-22.2 nanometer and constant Ti to Ni sublayer thickness ratio. Spectral and sublayer-thickness dependence of the magneto-optical properties of the Ti/Ni MLF.

A synthetic pathway to the formation of 3-amino-5-hydroxybenzoic acid is proposed. The scheme involves mainly a modified DAHP synthase with an additional protein subunit which likns and hydrolyzes glutamine to yield a molecule of ammonia in its active site. A Schiff base with erythrose 4-phosphate is formed and subsequent condensation with phosphoenolpyruvate yields 3,4-dideoxy-4-amino-D-arabino-heptulosonic acid 7-phosphate. Cyclization and dehydration gives 5-deoxy-amino-3-dehydroshikimic acid, which aromatizes to the target compound.

The anisotropic magnetoresistance (AMR) model is improved in order to determine the quality and direction of rotatable anisotropy in FeMn/NiFe structures independent of the thickness of the antiferromagnet layer. The properties of the rotatable anisotropies due to unstable antiferromagnet (AF) grains can be explained with the help of the values of two important parameters, magnitude and direction.

Background Immune checkpoint blockade with Programmed cell death 1 (PD-1)/PD-L1 inhibitors has been effective in various malignancies and is considered as a standard treatment modality for patients with non-small-cell lung cancer (NSCLC). However, emerging evidence show that PD-1/PD-L1 blockade can lead to hyperprogressive disease (HPD), a flair-up of tumor growth linked to dismal prognosis. This study aimed to evaluate the incidence of HPD and identify the determinants associated with HPD in patients with NSCLC treated with PD-1/PD-L1 blockade. Patients and methods We enrolled patients with recurrent and/or metastatic NSCLC treated with PD-1/PD-L1 inhibitors between April 2014 and November 2018. Clinicopathologic variables, dynamics of tumor growth, and treatment outcomes were analyzed in patients with NSCLC who received PD-1/PD-L1 blockade. HPD was defined according to tumor growth kinetics (TGK), tumor growth rate (TGR), and time to treatment failure (TTF). Immunophenotyping of peripheral blood CD8+ T lymphocytes was conducted to explore the potential predictive biomarkers of HPD. Results A total of 263 patients were analyzed. HPD was observed in 55 (20.9%), 54 (20.5%), and 98 (37.3%) patients according to the TGK, TGR, and TTF. HPD meeting both TGK and TGR criteria was associated with worse progression-free survival [hazard ratio (HR) 4.619; 95% confidence interval (CI) 2.868–7.440] and overall survival (HR, 5.079; 95% CI, 3.136–8.226) than progressive disease without HPD. There were no clinicopathologic variables specific for HPD. In the exploratory biomarker analysis with peripheral blood CD8+ T lymphocytes, a lower frequency of effector/memory subsets (CCR7−CD45RA− T cells among the total CD8+ T cells) and a higher frequency of severely exhausted populations (TIGIT+ T cells among PD-1+CD8+ T cells) were associated with HPD and inferior survival rate. Conclusion HPD is common in NSCLC patients treated with PD-1/PD-L1 inhibitors. Biomarkers derived from rationally designed analysis may successfully predict HPD and worse outcomes, meriting further investigation of HPD. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the influence of heat treatment on conventional magnetic properties and Barkhausen noise in ferromagnetic amorphous Fe[sub40]Ni[sub38]Mo[sub4]B[sub18]. Difference between ribbon and transverse directions of Barkhausen noise; Linear relationship between the magnetic anisotropy energy constant; Experimental procedures used.

The nucleotide sequences of the 16S rRNA gene of mitochondrial DNA for all the ape species were determined. On comparing this data with published sequences, all the ape species showed higher diversity than human.

The profiles of the second-order harmonics during B-H hysteresis loop have been measured as functions of the tensile stress and the angle [Phi] between H-field and [001] axis in 3% silicon steel. The observed harmonics profiles have been analyzed in terms of the nonlinear, asymmetric magnetic induction which reflects the domain reorientation under the field. The field interval of the second harmonics is related to the nucleation and annihilation fields and a measurement method for the magnetostriction is proposed using the harmonics profiles under tensile stress. Index Terms--Anisotropy field, annihilation field, magnetostriction, second harmonics.

The giant magnetoimpedance (GMI) is studied as function of annealing-field angle [[Theta].sub.k] in [Co.sub.66] [Fe.sub.4] Ni[B.sub.14] [Si.sub.15] ribbon with respect to transverse direction. The GMI profile at 10 MHz shows two peaks located at negative and positive external field H. The interval between two peaks, about 2.1 Oe for [[Theta].sub.k] = 0 [degrees], slightly increases with [[Theta].sub.k] up to [[Theta].sub.k] = 30 [degrees] and then decreases down to 1.0 Oe for [[Theta].sub.k] = 90 [degrees]. However, two peaks are asymmetric and hysteresis exists during cyclic magnetization. The asymmetry ratio, fractional difference of two peaks, is maximum about 2% for [[Theta].sub.k] = 10 [degrees] and its sign is reversed from [[Theta].sub.k] = 40 [degrees]. Index Terms--Amorphous ribbon, anisotropy, field annealing, magnetoimpedance.

The pinning field [H.sub.p] is obtained from the discontinuous variation of permeability according to ac magnetic field amplitude. The probability distribution of pinning field P([H.sub.p]) in 2605CO Metglas ribbon of as-quenched state shows a Gaussian distribution, indicating that the pinning sites with different pinning field are randomly distributed. The permeability spectra for pinned state of domain wall are caused by the pure rotational magnetization with 1 MHz relaxation frequency. For the magnetization overcoming the pinning field, the permeability spectra are superposition of rotational magnetization and wall displacement. The average pinning field and relaxation time of wall displacement decrease with the magnetizing angle from ribbon axis, and the relaxation times are found to be exponentionally proportional to the average pinning field. Index Terms - Amorphous ribbon, domain wall, pinning field, relaxation time.

The magnetoresistance (MR) in the spin-valve structure is analyzed on the basis of an equivalent circuit, in which two ferromagnetic layers representing the anisotropic magnetoresistance (AMR) effect are parallelly connected and the giant magnetoresistance (GMR) effect are serially connected. The measured MR profiles at angles of [Theta] = 0 [degree], 60 [degrees] and 90 [degrees] in NiO(30 nm)/NiFe(5 nm)/Cu(4 nm)/ NiFe(5 nm)/Ta(5 nm) spin-valve sample are in good agreement with calculated ones using the double domain model. As the magnetizing angle [Theta] increases, the AMR effect causing negative MR becomes significant. The AMR and GMR components in a spin-valve structure are decomposed using the double domain model. Index terms: AMR, double domain model, GMR, spin-valve

A differential probe which is used in the pulsed eddy current (PEC) system has been fabricated for the detection of wall thinning of insulated pipelines in a nuclear power plant (NPP). The differential PEC probe consists of two hall sensors in a differential arrangement. The tested sample is a stainless steel of thickness variation from 1 to 5 mm, the flat side of the sample is laminated by a plastic insulation having a uniform thickness to simulate the pipelines in NPP. The PEC response to varying metal thickness was measured at various thicknesses of insulations on the tested sample. The time-domain feature such as peak value of the detected pulse is used to interpret the thickness of the test sample. The signal analysis technique, such as power spectrum density, is applied to obtain an optimum parameter to describe the wall thinning of pipeline steel. This technique can be used as a potential tool to detect the corrosion or the wall thinning of the pipelines without removing the insulation. [ABSTRACT FROM AUTHOR]

The Ar ion has been irradiated by an ion implanter with energy of 50, 70, and 100 keV and an ion dosage was set to 1.0×1017 ion/cm2 at a beam flux of 3.7 μA/cm2. The ion irradiation decreased the initial permeability and increased the relaxation frequency, and the behavior of permeability spectra due to ion irradiation was explained with damped harmonic model of domain wall on the general basis of magnetization mechanism. The ion irradiation gives rise to a significant change on the restoring force of domain wall but minor effect on the spin rotation. The enhancement in the permeability of the amorphous ribbon upon ion irradiation leads to a parallel improvement of giant magneto impedance response of the material, which is of practical use for sensing applications. [ABSTRACT FROM AUTHOR]

The effects of ion irradiation on a giant magnetoimpedance (GMI) have been investigated for a Co-based amorphous ribbon with various kinds of ions such as Xe, Ar, and N. The GMI ratio and M-H loop parameters were used to characterize the samples before and after the ion irradiation. The GMI ratio increased considerably in the ion irradiated samples and the GMI response showed a strong dependence on the irradiated ion species and driving frequencies. It was shown that the ion irradiations lead to a substantial modification of the magnetic properties including a large coercivity and shearing of the in-plane magnetization loops, thus suggesting the reduction of an exchange coupling. [ABSTRACT FROM AUTHOR]

The magnetic hysteresis curves of NiFe(t)/FeMn(15 nm)/NiFe(5 nm) exchange-biased trilayers, with t ranging from 3.8 to 18 nm, show two clearly separated loops, which were interpreted as corresponding to the independent magnetic reversal of the two ferromagnetic (FM) NiFe layers. Polarized neutron reflectometry allowed the determination of the evolution of these two layer magnetizations at various fields along the hysteresis curve. For increasing t, the behavior of the magnetization evolved from one where both layer magnetizations were always collinear to the applied field to one where rotation of the magnetizations was observed at various fields. Measurements on the thickest field-annealed sample additionally showed that, during the reversal, the magnetizations of the two NiFe layers are close to being perpendicular to each other. This magnetic configuration is discussed in terms of the FM/antiferromagnetic (AFM) interactions and of a possible coupling between the two FM layers across the thick AFM FeMn spacer. [ABSTRACT FROM AUTHOR]

We investigated the magnetostatic and dynamic properties of annealed and etched Co[SUB66]Fe[SUB4]B[SUB15]Si[SUB15] amorphous ribbons. The near-surface magnetic characteristics of the annealed samples showed the gradual growth of a hard magnetic layer with increasing annealing time; that is, coercivity H[SUBc] and saturation field H[SUBs] increase from 15 to 600 Oe and from 45 to 1500 Oe, respectively. On the etching effect on the magnetic property in an 8 h annealed sample, the hard magnetic layer near the sample surface was retained for the sample with etching time t[SUBetch]<40 s, but the influence of the ribbon core on the near-surface magnetic properties of the sample was discovered for t[SUBetch]&ges;50 s. When the thickness of hard magnetic layer is about 1 μm, the asymmetric giant magnetoimpedance (GMI) profiles, the so-called GMI valve, do not show hysteresis. As the thickness is reduced, a hysteretic GMI is observed due to the cyclic change of magnetization in the hard magnetic layer under a cyclic field. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJ's) with Hf oxide and modified Hf oxide barriers were fabricated by ozone oxidation. The tunnel magnetoresistance (TMR) ratio in Hf oxide junction was 13% at room temperature and 21% at 77 K. In order to understand the low TMR ratio in MTJ's with Hf oxides compared to those with Al oxides, tunnel barriers were modified by inserting a thin Al oxide layer of 0.3 nm at the interfaces between ferromagnetic electrodes and Hf oxide insulating layers. As the Al layer of 0.3 nm was inserted at top and bottom interfaces, the TMR ratio was restored to the value of the junctions with Al oxides. This implies that the polarization of CoFe contacted with Al oxide is larger than that of CoFe contacted with Hf oxide and the low TMR ratio in MTJ's with Hf oxides may be attributed to the reduction of spin polarization of the CoFe electrodes due to CoFe/Hf oxide interface interaction. [ABSTRACT FROM AUTHOR]

GaMnN and Mg-codoped GaMnN films were grown in molecular beam epitaxy using a GaN single precursor. The structural, electrical, and magnetic properties were examined. The Mg-codoped GaMnN layers revealed room-temperature ferromagnetism. Codoping with Mg reduces the Mn incorporation, but increases the conductivity of the GaMnN films. At the same time, the saturation magnetization and coercivity have increased at room temperature. As this improvement was obtained with much reduced Mn concentration of ∼0.3%, the crucial role of the carriers for carrier-induced ferromagnetism in magnetic semiconductors is observed. [ABSTRACT FROM AUTHOR]

Experiments of the giant magnetoimpedance (GMI) profile have been performed in annealed amorphous Co[sub 66]Fe[sub 4]B[sub 15]Si[sub 15] ribbons in open air to characterize the role of the bias field on the GMI. The GMI ratio profile measured at 0.1 MHz exhibits a drastic step-like change, the so-called GMI valve, in an 8 h annealed sample at 380 °C. The GMI valve is related to exchange coupling of the bias field with magnetization of the soft amorphous phase, where the bias field is caused by hcp-Co and fcc-Co crystalline phases on the surface B and Si depleted layer. The bias field is stable for an external field less than 100 Oe, but its direction is entirely changed according to the external field over 400 Oe. The GMI profile begins to reveal hysteresis for increasing and decreasing cyclic fields when the maximum field strength exceeds 200 Oe. The peak for the increasing field is positioned in the negative field region, but in the positive field region for decreasing field. This behavior is opposite to general magnetic hysteretic characteristics, suggesting that there is an antiferromagnetic coupling of the bias field with magnetization of the inside amorphous phase. [ABSTRACT FROM AUTHOR]

For Co-Fe-Si-B amorphous ribbons the influence of weak-field annealing on transformation of magnetic field and spectral transverse Kerr effect (TKE) dependencies has been studied. The TKE spectra and magnetization curves were found to exhibit anisotropic behavior. The results indicate that the magnetic structure is inhomogeneous relative to thickness and confirm an increase of anisotropy in the near surface layer. It is suggested that the anisotropy is brought about by the shape effect of magnetic microcrystallites in the surface layer, the shape and size of which both change during annealing. [ABSTRACT FROM AUTHOR]

The complex permeability spectra and the magnetoimpedance (MI) are measured as a function of torsional stress and torsion angle in Fe[sub 77.5]Si[sub 7.5]B[sub 15] amorphous wire. The permeability spectra show irreversible and reversible relaxation with relaxation frequencies of 40 and 300 kHz, respectively. The static permeability resulted from the irreversible magnetization decreases with torsion angle for a negative direction, but increases with a positive angle. The MI profile shows one symmetric peak for the positive torsion angle, which is same MI behavior as in the case of zero torsion. However, there is a hysteresis in the MI profile for negative torsion, that is, there are two asymmetric peaks for decreasing field and one peak for increasing field. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The changes in soft magnetic properties on amorphous Fe[sub 73.5]Cu[sub 1]Nb[sub 3]Si[sub 13.5]B[sub 9] alloy after neutron irradiation are studied by complex permeability spectra, magnetoimpedance ions and M–H curve measurements. The total integration fluence of fast neutrons (n[sub f],E[sub n]>1 MeV) is varied from 1.92×10[sup 14]n[sub f] cm[sup -2] to 4.85×10[sup 16]n[sub f] cm[sup -2]. Two different types of relaxation processes in permeability spectra, which were observed in low and high frequency regions, are related to the domain wall motion and the rotational magnetization, respectively. As neutron irradiation fluence increases, the permeability due to domain wall motion decreases but the permeability due to rotational magnetization increases. The anisotropy field estimated from magnetoimpedance profile decreases with neutron irradiation fluence. The measurement of M–H curves shows the improvement of softness after neutron irradiation of 4.85×10[sup 16]n[sub f] cm[sup -2], due to the enhancement of rotational magnetization. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper, carbon/epoxy composites were employed as a potential candidate for spacecraft structural shielding along with the new concept of geometric configurations according to the threat severity to maximize the impactor energy absorption to improve performance. Carbon/epoxy composites of quasi-isotropic 16 layers [0/ ± 45/90]2s were manufactured using an autoclave, and the specimens were exposed to a low Earth orbit environment, which produced an average total mass loss of 0.42%, mainly due to outgassing. Al2017-T4 spherical projectiles with a diameter of 5.56 mm weight of 0.25 g were used as the impactor in the velocity range of 1500 ± 500 m/s. Earlier experimentations showed the superiority of obliquity towards energy absorption for single bumpers. Double bumpers with one 45° obliquity at 100 mm standoff absorbed 14% more specific energy than double bumpers with one at 30°; both of them were found to be superior to normal–normal bumpers by 40% and 30% on average, respectively. By CSCAN, it was also found that oblique impact on the first bumper resulted in less damage on the rear bumper and resulted in the superiority of the proposed geometric configurations, which enabled enhanced protection and designs according to threat severity. [ABSTRACT FROM AUTHOR]