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Electric-field control of perpendicular magnetic anisotropy (PMA) is a feasible way to manipulate perpendicular magnetization, which is of great importance for realizing energy-efficient spintronics. Here, we propose a novel approach to accomplish this task at room temperature by resistive switching (RS) via electrochemical metallization (ECM) in a device with the stack of Si/SiO2/Ta/Pt/Ag/Mn-doped ZnO (MZO)/Pt/Co/Pt/ITO. By applying certain voltages, the device could be set at high-resistance-state (HRS) and low-resistance-state (LRS), accompanied with a larger and a smaller coercivity (H C), respectively, which demonstrates a nonvolatile E-field control of PMA. Based on our previous studies and the present control experiments, the electric modulation of PMA can be briefly explained as follows. At LRS, the Ag conductive filaments form and pass through the entire MZO layer and finally reach the Pt/Co/Pt sandwich, leading to weakening of PMA and reduction of H C. In contrast, at HRS, most of the Ag filaments dissolve and leave away from the Pt/Co/Pt sandwich, causing partial recovery of PMA and an increase of H C. This work provides a new clue to designing low-power spintronic devices based on PMA films.

Fe3O4, as a half-metallic ferrimagnetic material, is believed to be one of the most promising materials in spin transport for spintronics. However, fabricating stoichiometric Fe3O4 film is still challenging because the oxidation is hard to control for various preparing methods. In this paper, series of Fe3O4 thin films on Si (100) substrates are grown by sputtering from a Fe3O4 target without oxygen atmosphere at different growth temperature and then extra heat treatment in high vacuum. By combining X-ray diffractometer (XRD), Raman spectrum, X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism, VSM analysis, we see that the structure and magnetic moment of Fe3O4 film are not only related with growth temperature during sputtering, but also refer to the temperature of post-heat treatments. When the growth temperature is lower than 300 °C, the film does not show any XRD diffraction peaks. When the growth temperature increases from 300 to 500 °C, the film shows the (111) texture of Fe3O4 film clearly. However, the other XRD diffraction peaks are observed after post-heat treatment. The saturation magnetization increases with growth temperature and the largest saturation magnetization is 473 emu/cm3 for growth temperature of 450 °C and extra heat treatment, which is close to bulk Fe3O4. Our results suggest that a selectable method can be used to fabricate high magnetic moment of Fe3O4 thin film.

Electric field control of exchange bias (EB) plays an important role in spintronics due to its attractive merit of lower energy consumption. Here, we propose a novel method for electrically tunable EB at room temperature in a device with the stack of Si/SiO

Manipulation of exchange bias (EB) via spin-current-induced spin–orbit torque (SOT) is of great importance in developing full electric control spintronic devices. Here, we report on SOT-dominant manipulation of the interfacial antiferromagnetic spins and the related perpendicular EB (PEB) in the IrMn/Co1- xTb x (CoTb) bilayers with various Tb contents. No matter the magnetization of the ferrimagnetic CoTb layer is Co-dominant or Tb-dominant; all the samples were perpendicularly magnetized, and spontaneous PEB could be established during the isothermal crystallization of the IrMn layer. The SOT-induced EB switching could be accomplished with assistance of an in-plane or out-of-plane external magnetic field, associated with a monotonic reduction of the EB switching fraction by increasing x. This phenomenon is attributed to weakening of the interfacial exchange coupling between the CoTb and IrMn layers as x is increased. These findings provide a way to design high energy-efficient spintronic devices by employing the antiferromagnet/ferrimagnet bilayers, which may have weak stray field and strong robustness in contrast to commonly used heavy-metal/ferromagnet/antiferromagnet trilayers.

The spin dynamics modulation has attracted extensive attention in the past decades. Rare-earth (RE) metals are essential participants in this context due to the large spin–orbit coupling. Here, with neodymium (Nd) capping, we achieve the enhancement on spin dynamic damping of Co40Fe40B20 (CFB) films by three times larger than that of CFB single layer. Based on the spin pumping theory, the interfacial spin mixing conductance [Formula: see text] is calculated as 7.3 × 1015 cm−2, which is one order larger than that of CFB/Pt. It leads to the large spin current transparency at CFB/Nd interface. By comparing of the resistivity of each layer, we found that the matched resistivity at two sides of the CFB/Nd interface plays an important role in the enhancement of [Formula: see text]. As a consequence, a high spin transparency of the CFB/Nd interface is obtained as 82%. In addition, damping enhancement of CFB is not changed promptly by inserting 1–2 nm Cu layer, but it is suppressed when the Cu layer is thicker than 3 nm, which is related to the thickness dependence of the Cu resistivity. Our study broadens the horizon for the application of rare-earth (RE) in spintronics.

Plasmonic metal-semiconductor nanostructures endow them with an enormous potential application in photocatalysis, however, the uniform deposition of metal NPs as small as a few nanometers remains a challenge. Here, we demonstrate the effectiveness of two-step polymer-network gel process in the synthesis of Ag-ZnO nanocatalyst with superior photocatalytic properties. Because of uniform distributed Ag NPs, large specific surface area and abundant surface oxygen vacancies, the Ag-ZnO nanoparticles exhibit a super high photocatalytic efficiency in comparison to pure ZnO nanoparticles. The efficiency can be further improved by optimizing the external factors, such as catalyst dosage, ambient temperature and initial solution pH. Good stability and practicability indicate its potential application in environmental purification. Our work does not only provide a feasible strategy for the synthesis of high property Ag-ZnO nanophotocatalysts, but also enriches the understanding of metal-metal oxide nanostructures.

Amorphous CoFeB films grown on GaAs(001) substrates demonstrating significant in-plane uniaxial magnetic anisotropy were investigated by vector network analyzer ferromagnetic resonance. Distinct in-plane anisotropy of magnetic damping, with a largest maximum-minimum damping ratio of about 109%, was observed via analyzing the frequency dependence of linewidth in a linear manner. As the CoFeB film thickness increases from 3.5 nm to 30 nm, the amorphous structure for all the CoFeB films is maintained while the magnetic damping anisotropy decreases significantly. In order to reveal the inherent mechanism responsible for the anisotropic magnetic damping, studies on time-resolved magneto-optical Kerr effect and high resolution transmission electron microscopy were performed. Those results indicate that the in-plane angular dependent anisotropic damping mainly originates from two-magnon scattering, while the Gilbert damping keeps almost unchanged.

Fe3O4 nanomaterials have attracted lastest interests due to their excellent properties and potential applications. In this paper, the thermal excitation is investigated by Mossbauer spectra and first principle calculations. Fe3O4 nanoparticles with uniform size, regular shape and good dispersibility are prepared by the solvothermal methods, and Fe3O4@SiO2 composite magnetic particles with layers of mesostructured SiO2 structure are assembled by improved Stober method. The particle size is 500 nm and the shell thickness of SiO2 layer is 80 nm. Fe3O4@SiO2 composite magnetic particles are then annealed at different temperature of 200 °C, 400 °C and 600 °C. The experimental measurements exhibit that the grain size grows up, and the magnetization is enhanced significantly, with increasing heat treatment temperature. However, Mossbauer spectra show that the relative absorption intensity in B-site fast decreases as increasing heat treatment temperature, from 64% at room temperature to 27% at 600 °C, indicating that large amount of Fe vacancies may form in B-site, and correspondingly, the net magnetic moment due to the difference of amount of Fe in B and A sites would be reduced, which strongly disagrees with the results of magnetization measured by vibrating sample magnetometer. In order to find the mechanism behind magnetization, the first-principle calculations are performed and reveal that the oxygen ions in the SiO2 shell may go into Fe3O4 core, which causes number of Fe2+ ions to decreases and transfer to Fe3+ ions, leading to the increase of magnetic moment. So we classify the difference between the amount of Fe3+ and Fe2+ ions in B-site as γ-Fe2O3. Based on this, Mossbauer spectra analysis presents quantitatively the concentration of various phase and their hyperfine interactions. This work provides a method to analyze the magnetic moment of Fe3O4.

The realization of perpendicular magnetization and perpendicular exchange bias (PEB) in magnetic multilayers is important for the spintronic applications. NiO(t)/[Ni(4 nm)/Pt(1 nm)]2 multilayers with varying the NiO layer thickness t have been epitaxially deposited on SrTiO3 (001) substrates. Perpendicular magnetization can be achieved when t < 25 nm. Perpendicular magnetization originates from strong perpendicular magnetic anisotropy (PMA), mainly resulting from interfacial strain induced by the lattice mismatch between the Ni and Pt layers. The PMA energy constant decreases monotonically with increasing t, due to the weakening of Ni (001) orientation and a little degradation of the Ni–Pt interface. Furthermore, significant PEB can be observed though NiO layer has spin compensated (001) crystalline plane. The PEB field increases monotonically with increasing t, which is considered to result from the thickness dependent anisotropy of the NiO layer.

Interfacial effect of amorphous cobalt-iron-boron (Co60Fe20B20) films deposited on GaAs(001) by DC magnetron-sputtering has been precisely studied. In-plane uniaxial magnetic anisotropy (UMA) as a significant magnetic property has been found in Co60Fe20B20/GaAs heterostructure and the UMA field (Hu) of (∼75 Oe) is achieved. Magnetic Schottky barrier contact has been achieved by current-voltage (I–V) characteristic through the interface with a barrier height of 0.72 eV, which is an appropriate for tunneling injection of spin current from ferromagnet to semiconductors in spin-injection devices.

In-plane uniaxial magnetic anisotropy (UMA) has been studied on a series of amorphous Co 56Fe 24 B 20 (CoFeB) films deposited on GaAs(001) substrates. With the increasing of the CoFeB thickness from 3.5 to 20.0 nm, it was found that a large uniaxial anisotropy field (H k) of about 270 Oe decreases monotonically to a relatively small value of about 100 Oe. The thickness dependence of H k coincides with the common interface-induced UMA model. The magnetization reversal processes of this series of CoFeB films were also investigated. The evolution of the thickness-dependent magnetization reversal mechanisms was briefly discussed in terms of the Stoner-Wohlfarth model, the pinning of domain wall model, and the modified Kondorsky model.

Tuning magnetic damping constant in dedicated spintronic devices has important scientific and technological implications. Here we report on anisotropic damping in various compositional amorphous CoFeB films grown on GaAs(001) substrates. Measured by a vector network analyzer-ferromagnetic resonance (VNA-FMR) equipment, a giant magnetic damping anisotropy of 385%, i.e., the damping constant increases by about four times, is observed in a 10-nm-thick Co40Fe40B20 film when its magnetization rotates from easy axis to hard axis, accompanied by a large and pure in-plane uniaxial magnetic anisotropy (UMA) with its anisotropic field of about 450 Oe. The distinct damping anisotropy is mainly resulted from anisotropic two-magnon-scattering induced by the interface between the ferromagnetic layer and the substrate, which also generates a significant UMA in the film plane.

In BiFeO3-based ferromagnet/anitferromagnet (FM/AFM) bilayers, field cooling is required through the Neel temperature to achieve significant exchange bias (EB) at room temperature (RT). In this work, NiFe2O4/BiFeO3 (NFO/BFO) all-oxide bilayer films were selected and deposited on SrTiO3 substrates by pulsed laser deposition to avoid the possible interfacial oxidization during the field cooling process. In combination with X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM) characterizations, the NFO/BFO bilayers are shown to have good crystalline layered structure. After field cooling at various temperatures, the samples show sizable EB effect at low temperature region, which is attributed to spin-glass-pinned effect. More importantly, significant EB can be obtained at RT after the sample was field cooled from temperatures higher than 400 K. The maximal values of the exchange bias field (HE) and the ratio between HE and coercivity (i.e. HE/HC) are 48 Oe and 0.6 at RT, respectively. The EB effect at RT is considered to result from the pinned and uncompensated spins near the NFO-BFO interface.

Two types of electric control of exchange bias (EB) by resistive switching (RS), i.e. conductive-filament-RS (type I) and interface-barrier-RS (type II) were observed in the Si/SiO2Ti/Pt/FeOx/Co/ITO multilayer devices, which were fabricated by magnetron sputtering. It is difficult for the type I device to control EB, which may be due to that the quantity of conductive filaments is not enough to modify the antiferromagnetic structure of FeOx near the Co/FeOx interface. However, the electric control of EB can be accomplished in the type II device. Compared with low-resistance-state (LRS), the exchange bias field (HE) increases a little but the coercivity (HC) increases significantly at high-resistance-state (HRS). We consider that the migration of the oxygen vacancies under different voltages is able to mediate the interfacial barrier height, leading to the bipolar RS effect and the change of EB as well. This provides a way for designing new types of spintronic devices based on electric control.

Pinus massoniana, Cunninghamia lanceolata, and Phyllostachys edulis are the main afforesting species in the low hilly areas and valley of the southern Yangtze River for commercial purpose. Ecological problems such as the monotonous community structure and low biodiversity are common in these plantations. To understand the effect of forest harvesting gap on the understory plant diversity in the three plantations, different size gaps with identical habitats were conducted with cano-pies as control in the three plantations in Baiyun Mountain. The life form spectrum of plants and plant diversity were compared among the different forest gaps. The results showed that species richness was the highest in C. lanceolata plantation (57 species), followed by P. edulis plantation (53 species) and P. massoniana plantation (41 species) in two years after harvesting. In the early period, plant species were more abundant in the gaps than that in the controls in C. lanceolata and P. edulis plantations, but there was no significant difference between the gaps and the control in P. masso-niana plantation. The percentage of phanerophyte plants were significantly higher in the forest gaps covered 500 m马尾松、杉木和毛竹是长江流域低山丘陵地区的主要用材树种,其人工林群落结构简单和生物多样性低下是普遍存在的生态学问题.为了解采伐林窗对3种人工林林下植物多样性的影响,选择生境条件基本一致的3种林分,以林下为对照,比较了通过采伐获得的不同大小林窗间植物生活型构成和多样性差异.结果表明: 采伐林窗后2年,3种林分中杉木林的植物种类最多,达57种,其次是毛竹林(53种)和马尾松林(41种).在采伐林窗初期,杉木林和毛竹林林窗内物种数显著高于对照,但马尾松林林窗与对照没有显著差异.500 m

Self-consistent determination of the key parameters in spin-charge conversion via spin pumping–induced inverse spin Hall effect., Spin Hall angle (θSH) and spin diffusion length (λsd) are the key parameters in describing the spin-charge conversion, which is an integral part of spintronics. Despite their importance and much effort devoted to quantifying them, significant inconsistencies in the reported values for the same given material exist. We report a self-consistent method to quantify both θSH and λsd of nonmagnetic materials by spin pumping with various ferromagnetic (FM) pumping sources. We characterize the spin-charge conversion for Pt and Pd with various FM combinations using (i) effective spin-mixing conductance, (ii) microwave photoresistance, and (iii) inverse spin Hall effect measurements and find that the pumped spin current suffers an interfacial spin loss (ISL), whose magnitude varies for different interfaces. By properly treating the ISL effect, we obtained consistent values of θSH and λsd for both Pt and Pd regardless of the ferromagnet used.

The exchange bias (EB) training effect, referring to the exchange field (H E) and/or the coercivity (H C) decreasing with the magnetic cycle (n), is often accompanied with EB. Usually, the EB training effect has different types, showing that H C1 (coercive field at the descending branch) and H C2 (coercive field at the ascending branch) change with n differently. In order to understand the origin producing the training type, a phenomenological model is therefore proposed. According to this model, how H C1 (or H C2) changes with n is determined by the change of pinning magnetization at the descending (or ascending) branch during the training process. For verifying the validity of our model, various experimental training results with respect to different exchange-biased systems are selected for fitting and all the fitting results are nearly perfect.

We report a method to switch both the circulation and polarity of magnetic vortices in a controlled manner within a nanosecond utilizing micromagnetic simulations. The controllable switching is achieved with the combination of two different types of magnetic field pulses on submicron permalloy disks with heptagonal shape. When a magnetic field pulse of ~100 mT is applied along one of the edge directions of the heptagon, the circulation of the vortex can be manipulated according to the pulse direction. When a pair of pulses with a few tens of mT in magnitude and relative delay of about 100 ps is applied in orthogonal directions, the polarity can be further controlled without influencing the circulation. The different magnitude of switching fields allows for the combination of both types of pulses in the control of both the circulation and polarity of magnetic vortices. The switching mechanism and the controlling parameters for disks with diameters of 500 and 700 nm are discussed.

Fe3O4 particles with uniform size, regular shape and good dispersibility are prepared by solvothermal methods. The size of Fe3O4 particles and their magnetic properties can be adjusted during synthesis. Fe3O4@SiO2 composite magnetic particles with layers of mesoporous SiO2 structure are assembled by improved Stöber method. The different shell thickness of SiO2 layer can be adjusted from 35∼150 nm using multi-coating by changing the content of TEOS to form Fe3O4@nSiO2@mSiO2. The Mössbauer spectra show that Fe3O4 particles are almost stoichiometric. However, it is found that the coverage of SiO2 have a significant effect on the occupation of Fe ions in Fe3O4 particles. Peroxidation appears in Fe3O4@SiO2 composite magnetic particles, which might be caused by oxygen in SiO2 layer during wrapping process.

We systematically studied the size-dependent quantum diffusion of Gd atoms within Fe circular quantum corrals on Ag(111). By varying the size of the quantum corrals, different types of patterns are observed inside the corrals, including a single dot and circular orbits for the diffusion of Gd adatoms. In addition, the motion of the adatoms also forms circular-like orbits outside the corral. Via quantitative analysis, we confirm that the regions with adatoms' high visiting probability are consistent with the positions of the local electronic density-of-states maxima, both inside and outside the corrals within a

A clear exchange bias has been observed at room temperature in a series of BiFeO3(t)/NiFe(3.6 nm) bilayers, in which the BiFeO3 layers are single-phase polycrystalline with t varied from 8 nm to 240 nm. With increasing t, both the exchange bias field (H E ) and the coercivity (H C ) increase sharply and approach maxima when t is about 40 nm, which is close to one half the spin cycloidal modulation period (64 nm) of the bulk BiFeO3 material. The oscillatory variations of H E and H C with the BiFeO3 layer thickness suggest that the cycloidal spin structure may exist in polycrystalline BiFeO3 thin films. The angular dependence of the exchange bias exhibits collinear unidirectional and uniaxial anisotropies in the present BiFeO3/NiFe bilayers.

With scanning tunneling microscopy, we experimentally demonstrate the self-organized Gd atomic superlattice on Ag(111) surface at low temperature. The diffusion barrier of a single Gd adatom and the long-range interaction between Gd adatoms on Ag(111) are determined. With these parameters, the formation mechanism is discussed and we confirm the validity of the previous discussed preconditions for formation of a good superlattice. The well-ordered structure is reproduced by the kinetic Monte Carlo simulations with the experimentally determined parameters. As well-ordered superlattice is realized in two different lanthanide adatoms on Ag(111), we predict that similar self-organization could form in other lanthanide adatoms because of their identical electron configuration in the outer shell and similar atomic radii.

Utilizing epitaxial Co2Fe1-xMnxAl full-Heusler alloy films on GaAs (001), we address the controversy over the analysis for the split hysteresis loop which is commonly found in systems consisting of both uniaxial and fourfold anisotropies. Quantitative comparisons are carried out on the values of the twofold and fourfold anisotropy fields obtained with ferromagnetic resonance and vibrating sample magnetometer measurements. The most suitable model for describing the split hysteresis loop is identified. In combination with the component resolved magnetization measurements, these results provide compelling evidences that the switching is caused by the domain wall nucleation and movements with the switching fields centered at the point where the energy landscape shows equal minima for magnetization orienting near the easy axis and the field supported hard axis.

We review recent studies by different experimental means of ultrathin films, exhibiting thickness-driven spin reorientation transitions (SRTs). The stage is set by determining, via phenomenological thermodynamic description, of the relevant phase diagrams for the possible types of SRT with and without applied magnetic field. Suitable representation may be chosen such that best use is made of the linear character (under thickness variation) of the system’s path in anisotropy space. The latter involves higher-order bulk and surface anisotropies in a substantial way. We examine sensitive experimental techniques for the detection and quantification of SRTs, such as hysteresis measurements with magneto-optical Kerr effect (MOKE), micromagnetic studies utilizing scanning electron microscopy with polarization analysis (SEMPA), photoemission electron microscopy (PEEM) and spin-polarized low-energy electron microscopy (SPLEEM) as well as ac magnetic susceptibility measurements via MOKE. Key issues are conclusively discussed including the identification of reliable experimental fingerprints about whether a given SRT proceeds via a phase of coexistence or via a cone (canted) phase. We demonstrate how the application of the general theoretical ideas to carefully designed measurements leads to the determination of the most important material parameters in any ultrathin-film SRT, namely, the surface (interface) magnetic anisotropy constants. The review concludes by our personal outline for future promising work on SRTs.

In this article, a novel single-column atmospheric cryogenic air separation process is proposed to reduce energy consumption through the implementation of thermal pump technique. Different from the conventional double-column cryogenic process, the new single-column distillation includes a nitrogen compressor acting as a thermal pump, which makes use of the latent thermal energy of the streams in the distillation column. To verify the validity of the proposed separation process, four typical configurations of the single-column processes are constructed and simulated on the ASPEN PLUS platform with the operation conditions: air flow rate at 50 000 N m3, inlet temperature of the distillation column at 87 K, and various nitrogen compression temperatures. The conventional double-column cryogenic air separation process is also simulated as the base to compare the energy consumptions between the conventional and the novel processes. On the basis of such a comparison, the novel single-column cryogenic air separat...

Nine avian influenza A viruses (AIVs), H1N2 (n = 2) and H1N3 (n = 7), were isolated from domestic ducks in live poultry markets in Zhejiang Province, Eastern China, in 2011. All viruses were characterized by whole genome sequencing with subsequent phylogenetic analysis and genetic comparison. Phylogenetic analysis of all eight viral genes showed that the viruses clustered in the Eurasian lineage of influenza A viruses. The hemagglutinin cleavage site of all viruses displayed features of a monobasic cleavage site. Although there was no evidence of re-assortment in subtype H1 AIVs among the avian species and mammalian hosts in this study, continued surveillance is needed considering the important role of the domestic duck in the dissemination and re-assortment of AIVs.

Electric control of exchange bias (EB) is of vital importance in energy-efficient spintronics. Although many attempts have been made during the past decade, each has its own limitations for operation and thus falls short of full direct and reversible electrical control of EB at room temperature. Here, a novel approach is proposed by virtue of unipolar resistive switching to accomplish this task in a Si/SiO2 /Pt/Co/NiO/Pt device. By applying certain voltages, the device displays obvious EB in the high-resistance-state while negligible EB in the low-resistance state. Conductive filaments forming in the NiO layer and rupturing near the Co-NiO interface are considered to play dominant roles in determining the combined resistive switching and EB phenomena. This work paves a new way for designing multifunctional and nonvolatile magnetoelectric random access memory devices.

A considerable in-plane uniaxial magnetic anisotropy (UMA) field (Hu ∼ 300 Oe) could be achieved when the amorphous CoFeB film was deposited on the GaAs(001) wafer by magnetron-sputtering after proper etch-annealed procedure. In order to get deep insights into the mechanism of the UMA, the film was annealed at different temperatures and the evolution of the in-plane magnetic anisotropy was investigated carefully. With increasing the annealing temperature (TA), the UMA could be maintained well when TA reached 250°C, but became very weak at 300°C. However, when TA was elevated to 400°C, another UMA (Hu ∼ 130 Oe) was built accompanied with a fourfold magnetic anisotropy with its strength of about 50 Oe. In terms of the magnetic anisotropy evolution along with TA, the anelastic strain, which is thought to be resulted from the interfacial interaction between CoFeB and GaAs, may play a dominant role in producing the enhanced UMA based on the ‘bond-orientational’ anisotropy (BOA) model.

ZnO nanoparticles (NPs) are synthesized by deoxidizing ZnO powder in a vacuum drying process. This process reduces the size of the NPs and increases the concentration of oxygen vacancies on their surfaces. ZnO NPs with sufficient oxygen vacancies are highly effective for the photodecomposition of methylene blue (MB) dye in water under ultraviolet irradiation. The MB degradation efficiency exceeds 99 percent after 50 min of light irradiation, and the catalytic property of the NPs remains stable over several complete degradation cycles. It is revealed that the concentration of oxygen vacancies on the surface, and the photocatalytic activity, are both higher for smaller NPs. Oxygen vacancies reduce the recombination rate of photo-generated charge carriers by capturing the electrons and hence, improve the efficiency of redox reactions. In addition, a smaller particle size leads to a larger specific surface area and a higher photonic efficiency for the ZnO NPs.

Iron–iron oxide granular films are fabricated using dc magnetron sputtering. Their structural, magnetic and transport properties are studied in the vicinity of percolation threshold. X-ray photoelectron spectroscopy and transmission electron microscopy confirm the coexistence of iron and FeOx. Magnetic measurement indicates the exchange coupling between the iron and the FeOx matrix. Metal–insulator transition is observed. The non-monotonic temperature dependencies of resistivity occur near the percolation threshold and the mechanism is investigated with the longitudinal and transverse magnetic transport measurement in terms of weak localization.

We report on the experimental and theoretical studies of cooling field (HFC) and temperature (T) dependent exchange bias (EB) in FexAu1 − x/Fe19Ni81 spin glass (SG)/ferromagnet (FM) bilayers. When x varies from 8% to 14% in the FexAu1 − x SG alloys, with increasing T, a sign-changeable exchange bias field (HE) together with a unimodal distribution of coercivity (HC) are observed. Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE ∼ T curve to move leftwards and upwards. In the meanwhile, HFC variation has weak effects on HC. By Monte Carlo simulation using a SG/FM vector model, we are able to reproduce such HE dependences on T and HFC for the SG/FM system. Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.