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${\mathrm{Sr}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$ hosts a novel ${J}_{\mathrm{eff}\phantom{\rule{4pt}{0ex}}}=1/2$ Mott state and quasi-two-dimensional antiferromagnetic order, providing a unique avenue of exploring emergent states of matter and functions that are extraordinarily sensitive to any structural variations. Although the correlation between the physical property and the lattice structure in ${\mathrm{Sr}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$ has been a focused issue in the past decade, a common perception assumes that the magnetic ordering is essentially determined by the Ir-O-Ir bond angle. Therefore, a delicate modulation of this angle and, consequently, a major modulation of the magnetic ordering by chemical doping, such as Ga at the Ir site, has been extensively investigated and well believed. In this paper, however, we present a whole package of structure and magnetism data on a series of single-crystal and polycrystalline ${\mathrm{Sr}}_{2}{\mathrm{Ir}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{O}}_{4}$ samples, revealing the substantial difference in the N\'eel temperature ${T}_{N}$ between the two types of samples, and the ${T}_{N}$ value for the polycrystalline sample $x=0.09$ is even 64 K higher than that of the single-crystal sample $x=0.09$ ($\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{N}}\ensuremath{\sim}64\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at $x=0.09$). Our systematic investigations demonstrate the crucial role of the c/a ratio in tuning the interlayer coupling and thereby the N\'eel point ${T}_{N}$, i.e., a higher ${T}_{N}$ can be achieved as c/a is reduced. The notable differences in structural parameters between the two groups of samples are probably caused by additional strain due to the massive grain boundaries in polycrystalline samples. The present paper suggests an additional ingredient of physics that is essential in modulating the emergent properties in ${\mathrm{Sr}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$ and probably other iridates.

We demonstrate that a bipolar non-volatile resistive switching behaviour with negative differential resistance (NDR) effect is realized in a Cu/BaTiO3/Ag device, which was deposited on a Si substrate via magnetron sputtering equipment. We suggest that the bipolar resistive switching is dominated by the trapping/detrapping of electrons at the BaTiO3–Cu interface. In addition, we demonstrate that the device exhibits good performance, including a large on/off ratio, high reliability and long retention time. Therefore, BaTiO3 may become a good candidate for application in resistive switching random access memory (RRAM) devices.

The conventional field cooling process for antiferromagnetic/ferromagnetic bilayer system might strongly damage the interface of BiFeO3 (BFO) with metallic ferromagnetic layer, leading to significant deterioration of exchange bias (EB). In this paper, a field cooling process with fast laser annealing has been proposed and applied on polycrystalline-BFO/Co bilayers, which can effectively modify the EB. In those samples with obvious EB, it is found that the exchange field (HE) increases abruptly when the laser fluence rises to a critical value, and decreases when the laser fluence is large enough. On the other hand, in those samples with negligible HE, EB could be easily induced after field cooling with proper laser fluence. In addition, the sign of HE could also be changed, depending on the direction of the cooling field. In contrast, after field cooling by conventional heat treatment, EB could be neither induced nor enhanced. The feasibility of fast laser annealing accompanied with field cooling to enhance or induce EB in the BFO/Co bilayer can be understood by much less interfacial diffusion in comparison with conventional field cooling.

In order to explore the effects of SnO2 content on the properties and microstructure of Ag/SnO2 electric contact materials with low silver content. A series of Ag/SnO2 electric contact materials with different SnO2 content were prepared and their arc erosion properties and physical properties were tested. The results show that with the decrease of Ag content, the hardness of Ag/SnO2 contact materials increases, and the conductivity and density decrease. When the Ag content is 88%, Ag and SnO2 enrichment zones are formed on the surface of the Ag/SnO2 contact material after arc erosion test. When the silver content is less than 82%, the surface microstructure of the Ag/SnO2 contact material after arc erosion is uniform, and no obvious Ag and SnO2 enrichment zones were formed, but cracks and pores increased.

Since the magnetic anisotropy of ferromagnetic (FM) films on semiconductor substrates has promising application for spintronics, it has stimulated extensive studies in the last two decades [1]. Remarkably, amorphous FM alloy films also exhibit uniaxial magnetic anisotropy (UMA) in the film plane when deposited on semiconductor substrates, e.g. CoFeB/GaAs (001) [2]. Although several models, including ‘bond-orientational anisotropy’ (BOA) model [2, 3] and random anisotropy model [4], have been proposed to explain the origin of UMA, the underlying mechanism has remained unclear yet. Considering that different cleavage plane of GaAs may have different inter-facial interaction with CoFeB film, a systematic investigation has been performed on the in-plane magnetic anisotropy of the CoFeB films deposited on different orientational GaAs substrates. Co 56 Fe 24 B 20 (CoFeB) films were deposited respectively on GaAs (001), GaAs (110) and GaAs (111) substrates by d.c. magnetron sputtering at room temperature. Before film growth, the surface contamination and oxides on the GaAs substrate should be removed by a standard procedure similar to that described in Ref. [5]. The base pressure was lower than 8.0×10−6 Pa and the Ar pressure was kept at 0.3 Pa during film deposition. A Ta film with 2 nm was deposited as capping layer to prevent the CoFeB film from oxidation. The magnetic hysteresis (M-H) loops were measured by a SQUID-VSM (Quantum Design). The angular dependence of M-H loop was measured by a vector VSM (Microsense EV7), from which the magnetic moment parallel (M x ) and perpendicular (M y ) to the field direction can be recorded simultaneously. All the measurements were performed in the film plane at room temperature.

The loop-stage-dependent exchange bias training effect has been systematically studied in the polycrystalline FeNi/FeMn bilayers. According to the ferromagnet (FM) magnetization states, an entire magnetic hysteresis loop can be divided into four different stages: 1) positive saturation stage; 2) descending branch; 3) negative saturation stage; and 4) ascending branch. The loop-stage-dependent training effect was studied by probing the instant variation of the exchange field and the coercivity after adding a short waiting time $\Delta t$ on a specific loop-stage. Our experimental results unambiguously show that this training effect strongly depends on the stage that the waiting time is assigned on and the quantity of $\Delta t$ as well. Based on the macroscopic two-level relaxation model, these phenomena can be well explained by considering different switching probabilities of the interfacial uncompensated antiferromagnetic spins during different FM magnetization reversal processes.

A 3.5 nm amorphous CoFeB film was sputtered on GaAs (001) wafer substrate without applying magnetic field during deposition, and a significant in-plane uniaxial magnetic anisotropy (UMA) field (Hu) of about 300 Oe could be achieved. To precisely determine the intrinsic Gilbert damping constant (α) of this film, both ferromagnetic resonance (FMR) and time-resolved magneto-optical Kerr effect (TRMOKE) techniques were utilized. With good fitting of the dynamic spectra of FMR and TRMOKE, α is calculated to be 0.010 and 0.013, respectively. Obviously, the latter is 30% larger than the former, which is due to the transient heating effect during the TRMOKE measurement. In comparison with ordinary amorphous CoFeB films with negligible magnetic anisotropies, α is enhanced significantly in the CoFeB/GaAs(001) film, which may be mainly resulted from the enhanced spin-orbit coupling induced by the CoFeB/GaAs interface. However, the significant in-plane UMA plays minor role in the enhancement of α.

Effective control of the domain wall (DW) motion along the magnetic nanowires is of great importance for fundamental research and potential application in spintronic devices. In this work, a series of permalloy nanowires with an asymmetric notch in the middle were fabricated with only varying the width (d) of the right arm from 200 nm to 1000 nm. The detailed pinning and depinning processes of DWs in these nanowires have been studied by using focused magneto-optic Kerr effect (FMOKE) magnetometer, magnetic force microscopy (MFM) and micromagnetic simulation. The experimental results unambiguously exhibit the presence of a DW pinned at the notch in a typical sample with d equal to 500 nm. At a certain range of 200 nm d d dependences, which may be originated from different potential well/barrier generated by the asymmetric notch with varying d.

Low-temperature heat capacity C(T) of the weakly electron-correlated SrNi2Ge2 122-layer compound undergoes a superconducting transition with onset at 1.4 K and a bulk T c =0.75 K, where heat-capacity jump ratio ΔC(T c )/γT c =0.88–1.05. A small average superconducting energy gap E g (ave)=2.21 kT c =0.14 meV is derived for this multi-gap superconductor. Similar results for isostructural SrPd2Ge2 include T c (onset)=3.5 K, bulk T c of 2.92 K, ΔC(T c )/γT c =0.70 and E g (ave)=2.54 kT c =0.64 meV. The higher T c onset could be associated with stoichiometric 1:2:2 grains in the polycrystalline samples. In addition, deviations of E g /kT c from the BCS ratio of 3.5 suggest that, just like their iron-based counterpart, these 122-layer germanides may also exhibit an unconventional, fully-opened multi-gap s-wave superconductivity.

Systematic studies of crystalline structure, magnetic and ferroelectric properties have been performed on polycrystalline Bi 0.8 La 0.2− x Pb x FeO 3 ceramic samples, in which x changes continuously from 0 to 0.2. Rietveld refinement of the x-ray diffraction (XRD) patterns shows that the compound crystal structure changes gradually from pseudotetragonal to pseudocubic with increasing Pb concentration. Coupled with the structural and compositional changes, magnetic ordering of the samples exhibits significantly non-monotonical variation corresponding to x . The compound remnant magnetization ( M r ) and coercivity ( H c ) both reach minimum values close to zero at x =0.07. This variation of magnetic property in co-doped samples can be attributed to the extent of suppression of cycloid spin structure in original BiFeO 3 with changing x . Unlike magnetic responses, the ferroelectric measurements show that the compounds have monotonical change in the remnant electric dipole polarization ( P r ).

FeCoGd(t)/AlO/FeCo magnetic tunneling junctions (MTJs) have been fabricated using a shadow mask by magnetron sputtering system on SiO2 wafer, with a simple oxidation in the atmosphere to the bottom electrode FeCoGd layer. From the transmission electron microscopy (TEM) with element content analysis, we found a serious oxidation of the Gd element at the FeCoGd/AlO interface. At room temperature, inverse/normal TMR effects and normal TMR effects were observed simultaneously in the low and high magnetic field region, respectively. The high field curves show superparamagnetic behaviour, which are difficult to be saturated. The saturation field increases with the increase of t. The low field normal or inverse TMR effect is mainly resulted from the existence of the compensation thickness of the FeCoGd layer at room temperature. However, the normal TMR effect in high field region mainly origins from the existence of a granular layer at the FeCoGd/AlO interface consists of FeCo-rich particles embedded in GdO insulating matrix. With the increase of the external magnetic field, the magnetic moments of the FeCo-rich particles in the granular layer gradually rotate to the field direction (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

LaAlO3 single crystals were doped with transition element Mn by thermal diffusion method for investigation of ferromagnetism. With increasing the annealing temperature TN, ferromagnetism begins to appear when TN equals 750 °C, which is indicated by small magnetic hystersis (M -H) loop with low coercive field of 60 Oe measured at 60 K. After TN arrives at 1300 °C, obvious M -H loop can be observed at 60 K and the M -T curve displays sharp Curie phase transition, which shows an unambiguous ferromagnetism. A bound magnetic polaron model was proposed to understand the observed ferromagnetic behavior in Mn-doped LaAlO3 single crystals. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Suppressing the stochastic domain wall (DW) motion in magnetic nanowires is of great importance for designing DW-related spintronic devices. In this work, we have investigated the pinning/depinning processes of DWs in permalloy nanowires with three different types of notches by using longitudinal magnetoresistance (MR) measurement. The averaged MR curves demonstrate that the stochastic DW depinning is suppressed partly or even completely by a transversely asymmetric notch. The single-shot MR curves show that how the resistance changes with the applied field also depends strongly on the notch type while the DW is pinned around the notch. In the case of two depinning fields, larger (smaller) change of resistance always corresponds to larger (smaller) depinning field, regardless of the notch type. These phenomena can be understood by that the spin structure around the notch changes differently with the notch type when the DW is traveling through the notch.

In order to improve production efficiency and product quality of epoxy fiberglass-reinforced plastic (FRP) pipes, the manufacturing system adopted internal heating curing process for FRP pipes was developed. This article introduces the mechanical structure and operating principle of the machine tool and establishes the coupled mathematical model of the temperature and curing degree during the curing process of filament winding FRP pipes. The numerical simulation program was developed by finite element software ANSYSL. The influence of pipe wall thickness, fiber volume fraction and convection coefficient on temperature and degree of cure distribution during curing process is simulated, which provides theoretical basis for the optimization of the curing process of FRP pipes.

Based on a new expansion technology for oriented polyvinyl chloride (PVC-O) pipes, the stress distribution in pipe wall during expansion and the efficiency of the heating process are analyzed theoretically. According to the results of theoretical calculation, the optimal parameter and strength variation for different expansion ratios are studied experimentally. Theoretical calculation results show that the hoop stress and radial stress in pipe wall are near-linearly distributed, and they are approximately equal. The heating efficiency is gotten by heat transfer calculations for different oil bath temperatures and heating times. After expansion, the intensity and Young's modulus are increased but elongation at break is reduced. All the variations in properties enlarge along with the raise of expansion ratio. Fine appearance and high-strength PVC-O pipe can be achieved by optimizing the expansion parameter. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 27:172–181, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20137

Iron/iron-oxide granular films were fabricated using reactive dc magnetron sputtering. Their structural, magnetic and transport properties were systematically studied. XPS and TEM confirmed the coexistence of Fe, FeO and Fe 2 O 3 . A metal–insulator transition was observed with the increasing of the oxygen component in the film. The temperature dependencies of longitudinal resistivity ρ xx and anomalous Hall resistivity ρ xy were discussed. We found the enhancement of ρ xy and investigated the scaling law between anomalous Hall coefficient R s and ρ xx . In all the samples, R s was found to be proportional to ρ xx when ρ xx is small, which indicated the skew scattering is dominant.

La0.67Ca0.33MnO3 (LCMO)/YBa2Cu3Oy (YBCO)/Ni trilayers were fabricated with varying thickness of the mid-superconducting YBCO layer. Two different deposition systems were used to avoid oxidation of the magnetic metal Ni and contamination of the deposition systems. Transport properties show that the temperature dependence of resistance goes from a metallic-to-metal-insulator transition (manganite-like behavior) to a superconducting behavior (M-M-S) with increase of the thickness of the YBCO layer. The magnetoresistance (MR) ratio is very small in comparison with LCMO/YBCO bilayers at low temperature. Such phenomenon may depend on the charge transfer and the magnetic spin interaction between the bottom and cap magnetic layers. (c) 2005 Elsevier B.V. All rights reserved.

In this paper, a new power bipolar transistor structure called the trench base-shielded bipolar transistor (TBSBT) Is proposed and experimentally demonstrated. This structure incorporates deep p/sup +/ poly-Si trenches into the base of a conventional bipolar transistor. With the base shielded effectively by the p/sup +/ trenches, the base of the TBSBT can be made very narrow to achieve high current gain h/sub FE/ and high cut-off frequency f/sub T/ without compromising on the breakdown voltage. Experimental results show that the on-state anti switching characteristics of the TBSBT are significantly better than those of the existing power bipolar transistors.

A multilayer magnetic quantum dot sample containing 5 layers of Fe quantum dots (QDs) embedded in six layers of ZnS spacer was grown by molecular beam epitaxy (MBE). High-resolution transmission electron microscopy (HRTEM) observations reveal that the Fe QDs are single crystalline with spherical shape of diameters around 3 to 4 nm and area density of 1.5times1012 cm-2. Its zero-field cooled (ZFC) and field cooled (FC) curves measured at low field (100 Oe) show the magnetic relaxation effect with a blocking temperature around 26 K. The hysteresis loop measured at 5 K shows a coercivity of 83 Oe, confirming the slow relaxation process and coercivity enhancement attributed to the nanoparticle nature of the sample

Comparison of the extraordinary Hall effect (EHE) on top and bottom NiO-pinning Co/Cu/Co spin valves (SVs), has been made in order to investigate the relationship Rs~rhon between the extraordinary Hall coefficient Rs and the resistivity rho. Bottom and top spin valves have stronger and weaker specular reflection effects which mainly originate from smoother and rougher Co/NiO interface, respectively. The scaling law Rs~rho2, which implies that the side-jump mechanism is the dominant scattering process, works fairly well (n=1.93plusmn0.02) in the bottom NiO-pinning spin valve, while it deviates much (n=1.32plusmn0.04) in the top one

Measurements of physical properties were performed on the PrBa2Cu4O8-δ sample prepared by the sol-gel method and sintered in I atm oxygen pressure. Instead of exhibiting superconductivity as for R Y or Gd in the RBa2Cu4O8-δ compound. This compound is unstable, insulating but metallic-like at low temperatures. No superconductivity was observed down to 2 K. Since PrBa2Cu4O8-δ can be re-written as Cu2Ba2PrCu2O8-δ which is a compound of two CuO2-layers and two CuO-chains, the possibility of anomalous Pr antiferromagnetic ordering around 18 K observed from preliminary magnetic data and the effect of oxygen stoichiotmetry parameter δ on the metal-insulator transition are explored.

Stochastic phenomena in magnetic nanowires based on domain wall (DW) motion is scientifically important thus to understand and control such behaviors are very meaningful. Here we report on the investigation of pinning and depinning of DWs in permalloy nanowires with six types of longitudinally asymmetric notches using focused magneto-optic Kerr effect (FMOKE) magnetometer and magnetic force microscopy (MFM). The hysteresis loops obtained by FMOKE indicate the generation of one or two distinct depinning fields by creating one notch close to the edge of the nanowires, in comparison multiple depinning processes occur in the nanowires with two identical notches symmetrically placed along the transverse direction, indicating more remarkable stochastic DW depinning phenomena. The MFM images verify the existence of DW in each type of nanowires and the DW sizes in the latter kind of nanowires are generally larger than those in the former ones. These observations can be explained by considering the thermal perturbation and edge or surface roughness effects in nanowires.

Magnetization reversal behavior in the exchange biased Co/FeMn bilayers with collinearly aligned ferromagnetic (FM) intrinsic anisotropy and induced interfacial anisotropy was investigated by angular resolved magnetic hysteresis loops measurements, and special attention was paid to the magnetization signals recorded perpendicular to the external magnetic field direction (M y ). During the angular magnetization reversal process, two critical angles were clearly observed. Around the easy axis, the magnetization reverses in a full circle, i.e., two M y peaks appear with opposite signs. In contrast, above a certain critical angle α c1, the magnetization reverses only in one semicircle, i.e., M y always remains positive or negative. Above another critical angle α c2, the heights of the two M y peaks becomes equivalent. The angular dependence of exchange bias (ADEB) was also carefully investigated. In order to understand the experimental reversal behaviors clearly, numerical simulations were performed based on a modified Stoner-Wohlfarth (S-W) model considering the collinear anisotropies in current samples. The calculated results unambiguously show that the angular dependent reversal behavior as well as the occurrence of two critical angles is originated from the strength competition between the FM intrinsic anisotropy and the field cool induced interfacial exchange anisotropy.

We have fabricated fully vacuum-sealed 5 in. diagonal carbon nanotube field-emission displays of a gated structure with reliable electron emission characteristics. Single-walled carbon nanotube tips were implemented into the gate structure using self-aligned backside exposure of photosensitive carbon nanotube paste. An onset gate electrode voltage for emission was about 60 V and the luminance as high as 510 cd/m2 was exhibited under an application of 100 V and 1.5 kV to gate electrode and anode, respectively.

Tunneling magnetoresistance (TMR) effect has been extensively studied either in MTJs [1] or in insulating granular films, but few studies have been reported on the composite structure combined them together. In this presented work, the MTJs of FeCoGd(t)/AlO/FeCo have been fabricated. Different from conventional MTJ, the FeCoGd electrode was partially oxidized. A thin granular film due to the oxidation is likely to be found at the interface between the FeCoGd electrode and the barrier. The TMR effects of the composite MTJs have been studied.

In this presented work, both top and bottom pinning FeNi/FeMn bialyers were prepared by sputtering with an external field applied in the film plane during deposition. The training processes were performed with a vector vibrating sample magnetometer (VVSM) through which Mx and My can be measured simultaneously. Before the tuning process, ten loops were measured at an angle of six degrees with respect to the initial PD, to eliminate the training effect to a very low extent. Then an in-plane tuning field of 600 Oe was applied perpendicular to the initial PD for five minutes. During the whole process, the rotation of the PD is identified with My = 0 and Mx = Maximum immediately after each M-H loop measurement and each tuning process [3].

Metastable filamentary superconductivity with Tc = 10.2 K was observed in SrPt2Ge2. This is the highest Tc reported outside the iron-based 122-layer compounds. The stable phase for this compound is a non-superconducting monoclinic LaPt2Ge2-type structure with lattice parameters a = 0.4401(4) nm, b = 0.4435(4) nm, c = 0.9764(10) nm, β = 90.5°–90°. Weak diamagnetic shielding signal indicates that superconductivity is not from the major monoclinic phase, but from the minor BaFe2As2-type body-center-tetragonal (122-bct) phase with a=0.44 nm, c=0.98 nm,β=90°. Investigation on the pseudoternary system Sr(Pd1−xPtx)2Ge2 suggests that the stable bct to monoclinic structure phase transition occurs near x = 0.15. For x 0.15 with metastable filamentary bct phase, Tc increases from 7.5 K for x = 0.5 to 9.2 K for x = 0.7 and reaches a Tc maximum of 10.2 K for SrPt2Ge2. High Tc is due to a strong quasi-2D Pt-Ge-Pt 5dxz,yz-...

We investigated the thickness-driven spin-reorientation transition (SRT) between in-plane and perpendicular easy axes in ultrathin magnetic films. Coherent rotation model calculations show that one can distinguish transition pathways via a canted state from those involving a state of coexisting phases by utilizing magnetic susceptibility measurements. Surface/interface anisotropy constants and the influence of external fields on the SRT are also explored. Quantitative agreement between the experiment and our model is shown for the Co/Au(111) system.

Anisotropic structural and magnetic properties of the field-aligned superconducting system SmFeAsO1−xFx (x = 0, 0.1, 0.2, 0.25 and 0.3) are reported. Due to the Fe spin-orbital related anisotropic exchange coupling, all the tetragonal microcrystalline powders in epoxy were aligned at room temperature using the field-rotation method where the tetragonal ab-plane is parallel to the magnetic alignment field Ba of 0.9 T and the c-axis parallels to the rotating axis. Anisotropic magnetic properties are studied through low temperature magnetic measurements along the c-axis and paralleled to the ab-plane of aligned samples in both zero-field-cooled (ZFC) and field-cooled (FC) modes. The under-doped compound (x = 0.1) is not superconducting with an antiferromagnetic Neel temperature TN ~ 40 K, while the two optimum-doped compounds (x = 0.2 and 0.25) show high superconducting transition temperatures Tc of 49K and 50K, respectively. The variation of anisotropic structural and magnetic properties for this system are discussed and compared with the previously reported 52 K anisotropic superconductor Sm0.95La0.05FeAsO0.85F0.15.

FeCoGd/FeCo(t)/AlO/FeCo magnetic tunnel junctions were fabricated with a very thin FeCo layer inserted between the FeCoGd layer and the AlO barrier. At room temperature, inverse tunneling magnetoresistance (TMR) effect and normal TMR effect were observed simultaneously in the low and high magnetic field regions, respectively. The absolute values of both inverse and normal TMR ratios, the saturation magnetic field corresponding to the normal TMR effect have similar dependence on t. Transmission electron microscopy studies indicate that a thin granular film is likely formed between the FeCoGd layer and the AlO barrier, which may result in the normal TMR effect at high magnetic fields.

A novel CrSe∕Fe bilayer structure has been fabricated on a GaAs (100) substrate by the molecular beam epitaxy technique. Microstructural characterizations have revealed that the Fe layer is a single-crystalline bcc structure with the orientation relationship of (100)Fe‖(100)GaAs, while the top CrSe layer shows four preferred hexagonal domains with their c axis each along one of the four upward-pointing ⟨111⟩ directions of the underlying Fe lattice. The magnetic hysteresis loops of this bilayer structure measured by a superconducting quantum interference device magnetometer demonstrate a strong exchange bias effect with a negative exchange bias field as high as −48.4Oe at 5K. The magnetization reversal process shows an abrupt transition nature at temperature from 5to300K. An enhancement of the coercivity not accompanied by the exchange bias field was observed at temperature higher than and well above the blocking temperature. We have interpreted these observations based on the well-established exchange spr...

High field (up to 5 T) magnetization measurements were performed on both bulk and field‐aligned powder samples of RNi2B2C (R=Dy, Ho) magnetic superconductors. For Tc=3.8 K, a DyNi2B2C superconductor with antiferromagnetic Neel temperature TN of 10–11 K, and anomalous field‐induced weak‐ferromagnetic transitions were observed above the superconducting upper critical field Hc2(2 K) of 1.75 kG. The aligned powders show distinct hysteresis characteristics for both fields applied parallel and perpendicular to the tetragonal basal plane. For Tc=7.8 K, HoNi2B2C has an incommensurate magnetic ordering temperature Tm of 6 K and TN of 5.2 K. Anomalous field‐induced weak‐ferromagnetic transitions were also observed below TN. No hysteresis can be detected for TN

The systematic variation of anomalous Pr antiferromagnetic ordering temperature T N (Pr) for the two‐CuO2‐layer cuprate system MA2PrCu2O y (M=Cu, Hg, Tl, Pb; A=Ba, Sr) was verified through the observation of a new Hg‐1212 HgSr2PrCu2O6+δ tetragonal compound with a T N (Pr) of 6 K and a Pr—O bond length of 2.492 A between Pr and oxygen in the adjacent CuO2 layers. For the tetragonal/orthorhombic 1212 compounds including the PrBa2Cu3O7−y system, T N (Pr) was found to decrease monotonically with increasing Pr—O distance. The importance of Pr‐O‐Pr superexchange magnetic coupling is expected for all two‐CuO2‐layer M m A2PrCu2O y m212‐type (m=1, 2, 3) compounds. A similar Pr anomaly in the 2212‐type system was first observed on the new tetragonal (Pb0.5Cu0.5)2(Ba0.5Sr0.5)2PrCu2O8 compound with a high T N (Pr) of 9 K.

Sustained-release microspheres of nitrendipine with hydroxypropylmethylcellulose phthalate (HP-55) having a solid dispersion structure were prepared by using the quasi-emulsion solvent diffusion method of the spherical crystallization technique. To investigate the effect of the additives in poor solvent on the preparation of the nitrendipine microspheres, three types of additives, i.e. C 12 H 25 ,NaO 4 S (sodium dodecyl sulfate), NaOH, and KH 2 PO 4 NaOH mixture, were chosen. The resultant microspheres were evaluated with respect to their recoveries, micromeritic properties and release rates. The mechanisms involved in the effect of different poor solvents on formation of the microspheres are discussed. The sustained-release nitrendipine microspheres could not be prepared without using any additives added to the poor solvent. The additives dissolved in poor solvent could affect the micromeritic properties and the release profiles of the resultant microspheres. On increasing the amount of additives, the total recoveries of microspheres were increased and the average diameter of the microspheres was reduced. It was found that a dissociation of HP-55 in poor solvent contributed to the formation of sustained-release nitrendipine microspheres. The release rate of the microspheres prepared with sodium dodecyl sulfate aqueous solution was slower than that of the other two additives, due to the more dense structure formed. Since HP-55, a pH-dependent polymer, was formulated in the present microspheres, the pH value of dissolution medium was one of critical factors to determine the dissolution rate.