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The SOLARIS synchrotron located in Krakow, Poland, is a third-generation light source operating at medium electron energy. The first synchrotron light was observed in 2015, and the consequent development of infrastructure lead to the first users’ experiments at soft X-ray energies in 2018. Presently, SOLARIS expands its operation towards hard X-rays with continuous developments of the beamlines and concurrent infrastructure. In the following, we will summarize the SOLARIS synchrotron design, and describe the beamlines and research infrastructure together with the main performance parameters, upgrade, and development plans.

The spectroscopy using synchrotron radiation is the advanced tool for materials characterization. In the current work we are reporting recent activity in this research field implemented at the 04BM (PEEM/XAS) beamline of the National Synchrotron Radiation Centre SOLARIS in Krakow, Poland. The beamline is designed to cover wide energy range of soft X-rays, which is well suited for a broad range of applications, including surface physics, material science and magnetism. The comparison of the experimental parameters and selected examples of the results achieved on the PEEM and XAS end stations is demonstrated.

A UHV-compatible MOKE magnetometer for in situ studies operating in tandem with the PEEM at the Nanospectroscopy beamline of the Elettra synchrotron., We report on a custom-built UHV-compatible Magneto-Optical Kerr Effect (MOKE) magnetometer for applications in surface and materials sciences, operating in tandem with the PhotoEmission Electron Microscope (PEEM) endstation at the Nanospectroscopy beamline of the Elettra synchrotron. The magnetometer features a liquid-nitrogen-cooled electromagnet that is fully compatible with UHV operation and produces magnetic fields up to about 140 mT at the sample. Longitudinal and polar MOKE measurement geometries are realized. The magneto-optical detection is based on polarization analysis using a photoelastic modulator. The sample manipulation system is fully compatible with that of the PEEM, making it possible to exchange samples with the beamline endstation, where complementary X-ray imaging and spectroscopy techniques are available. The magnetometer performance is illustrated by experiments on cobalt ultra-thin films, demonstrating close to monolayer sensitivity. The advantages of combining in situ growth, X-ray Magnetic Circular Dichroism imaging (XMCD-PEEM) and MOKE magnetometry into a versatile multitechnique facility are highlighted.

Fe and Ni compounds and their oxides offer stoichiometry-dependent magnetic properties, owing to an extremely rich variety of crystallographic phases and a complex phase diagram. They foster the fabrication of oxide/metal magnetic junctions with tunable coupling, thus avoiding the usage of costly materials such as Co and rare-earth elements. Along these lines, here, spectro-microscopy is employed to study the oxidation of FeNi alloy ultrathin films featuring laterally separated fcc and bcc phases. Under mild oxidation conditions at T < 250 °C, Fe segregates to the surface forming a thin superficial Fe-oxide layer, which eventually evolves to Fe3O4 supported on an interfacial FeNi oxide with a spinel structure. Notably, the bcc FeNi oxidizes faster than the fcc one, while the fcc/bcc phase boundary is found to be the most reactive surface region. The magnetic coupling and domain morphology of the oxide–metal heterostack, characterized by XMCD-PEEM and CEMS, are shown to depend on the crystallographic structure of the alloy film. In particular, the Fe-oxide layer on top of the fcc regions exhibits micron-sized uniform magnetic domains antiferromagnetically coupled to the metal support. In contrast, the corresponding oxide on the bcc regions displays fragmented magnetic domains at a length scale of about 100 nm, with ferromagnetic coupling to the underlying FeNi metal support. Our study identifies novel principles for engineering the magnetic coupling through the interface structure and chemistry, with potential applications in sustainable spintronics.

The influence of the grinding process on the magnetic properties of as prepared and functionalized multiwall carbon nanotubes (MWCNTs) is presented. We have observed that 3 h mechanical grinding at 400 rpm in contrast to functionalization does not remove the iron contamination from MWCNTs. However, it changes the Fe chemical states. The magnetic properties of iron nanoparticles (Fe-NPs) embedded in the carbon matrix of MWCNTs have been analyzed in detail. We have proven that single-domain non-interacting Fe(C,O)-NPs enriched in the Fe3C phase (~10 nm) enclosed inside these nanotubes are responsible for their magnetic properties. Mechanical grinding revealed a unique impact of -COOH groups (compared to -COONH4 groups) on the magnetism of functionalized MWCNTs. In MWCNT-COOH ground in a steel mill, the contribution of the Fe2O3 and α-Fe phases increased while the content of the magnetically harder Fe3C phase decreased. This resulted in a 2-fold coercivity (Hc) decrease and saturation magnetization (MS) increase. A 2-fold remanence (Mr) decrease in MWCNT-COOH ground in an agate mill is related to the modified Fe(C,O)-NP magnetization dynamics. Comparison of the magnetostatic exchange and effective anisotropy length estimated for Fe(C,O)-NPs allows concluding that the anisotropy energy barrier is higher than the magnetostatic energy barrier. The enhanced contribution of surface anisotropy to the effective anisotropy constant and the unique effect of the -COOH groups on the magnetic properties of MWCNTs are discussed. The procedure for grinding carboxylated MWCNTs with embedded iron nanoparticles using a steel mill has a potential application for producing Fe-C nanocomposites with desired magnetic properties.

We report on in-plane magnetic anisotropy in Au/Co/Fe(1 1 0) trilayers epitaxially grown on W(1 1 0). We observe single and double in-plane spin reorientation transitions that can be explained by the strongly non-monotonic dependence of magnetic anisotropy on the Co sublayer thickness. We point out the significant flexibility of the Au/Co/Fe(1 1 0) system for switching the in-plane easy axis of the magnetic anisotropy between the [ 1 1 ¯ 0 ] and [0 0 1] directions of the bcc(1 1 0) plane.

We analyzed the formation of biphase superstructures on the (111)-oriented epitaxial magnetite films on Pt(111) as a function of controlled film stoichiometry. The stoichiometry of the films severa...

Magnesium(II) and metal-free porphyrazines containing peripheral 2-methyl-5-phenyl- or 2,3,5-triphenyl-1H-pyrrol-1-yl substituents were synthesized and subjected to physicochemical characterization, including high-resolution mass spectrometry, nuclear magnetic resonance, HPLC purity analysis, and UV-Vis spectroscopy, accompanied by the aggregation study in dichloromethane and pyridine. Single crystals of magnesium(II) porphyrazines were subjected to X-ray structure analysis. The presence of atropisomers of magnesium(II) porphyrazines with peripheral 2-methyl-5-phenyl- or 2,3,5-triphenyl-1H-pyrrol-1-yl substituents was noticed in the NMR study and was confirmed by crystal structure determination. The NMR and X-ray data provided the evidence for the hindered rotation of the asymmetrical peripheral pyrrolyl substituents in magnesium(II) porphyrazines which resulted in obtaining compounds composed of different types of atropisomers, other than α4, preferentially α3β and αβαβ.

We show that in-plane to out-of-plane magnetization switching of a ferromagnetic layer can be driven by antiferromagnetic–ferromagnetic phase transition in a nearby FeRh system. For FeRh/Au/FeAu trilayers, the impact of the magnetic phase transition of FeRh onto the perpendicular magnetization of monoatomic FeAu superlattices is transferred across the Au spacer layer via interlayer magnetic coupling. The polar spin reorientation process of the FeAu spins driven by the magnetic phase transition in the FeRh reveals its major features; namely it is reversible and displays hysteresis.

We studied magnetite–hematite–magnetite transformations in an ultrathin epitaxial film on Pt(111) using surface sensitive and bulk sensitive methods. At initial oxidation stages at elevated temperature (810 K), a 5-nm thick magnetite Fe3O4(111) film became non-stoichiometric toward maghemite and then showed the first signs of hematite phase formation under an oxygen exposure of 3 × 103 L. Finally, under 2 × 104 L, the film fully transformed to hematite α-Fe2O3(0001), maintaining a high single-crystal quality. A comparison of the conversion electron Mossbauer spectra and low energy electron diffraction pattern showed that at intermediate oxidation stages, hematite dominated at the surface, whereas a spinel phase was still observed in the deeper layers. The magnetite–hematite conversion was fully reversed by annealing under ultra-high vacuum at temperatures exceeding 600 K, and despite a change in morphology, the magnetite film preserved the original crystal structure and orientation.We studied magnetite–hematite–magnetite transformations in an ultrathin epitaxial film on Pt(111) using surface sensitive and bulk sensitive methods. At initial oxidation stages at elevated temperature (810 K), a 5-nm thick magnetite Fe3O4(111) film became non-stoichiometric toward maghemite and then showed the first signs of hematite phase formation under an oxygen exposure of 3 × 103 L. Finally, under 2 × 104 L, the film fully transformed to hematite α-Fe2O3(0001), maintaining a high single-crystal quality. A comparison of the conversion electron Mossbauer spectra and low energy electron diffraction pattern showed that at intermediate oxidation stages, hematite dominated at the surface, whereas a spinel phase was still observed in the deeper layers. The magnetite–hematite conversion was fully reversed by annealing under ultra-high vacuum at temperatures exceeding 600 K, and despite a change in morphology, the magnetite film preserved the original crystal structure and orientation.

Gold clusters on an iron-modified rutile TiO

The common approach to modify the thermoelectric activity of oxides is based on the concept of selective metal substitution. Herein, we demonstrate an alternative approach based on the formation of multiphase composites, at which the individual components have distinctions in the electric and thermal conductivities. The proof-of-concept includes the formation of multiphase composites between well-defined thermoelectric Co-based oxides: Ni, Fe co-substituted perovskite, LaCo0.8Ni0.1Fe0.1O3 (LCO), and misfit layered Ca3Co4O9. The interfacial chemical and electrical properties of composites are probed with the means of SEM, PEEM/XAS, and XPS tools, as well as the magnetic susceptibility measurements. The thermoelectric power of the multiphase composites is evaluated by the dimensionless figure of merit, ZT, calculated from the independently measured electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (λ). It has been demonstrated that the magnitude’s electric and thermal conductivities depend more significantly on the composite interfaces than the Seebeck coefficient values. As a result, the highest thermoelectric activity is observed at the composite richer on the perovskite (i.e., ZT = 0.34 at 298 K).

High-temperature reorganization of the adsorbed oxygen on the W(110) surface was investigated using low-energy electron diffraction (LEED) and low-energy electron microscopy (LEEM). Using these two techniques, we have resolved two out of three high-temperature tungsten oxide phases reported in the literature. We verified the structural properties of oxygen adsorbed on tungsten by comparing bright- and dark-field LEEM images. In particular, we determined the relationship between atomic steps and the occurrence of a specific structural domain in different phases. Finally, we described the temperature-induced structural transformation that was directly observed, both in real and reciprocal space, for two oxygen surface phases formed on W(110). By careful examination, it was proven that under specific circumstances, this transition can be conducted in both directions, and it is possible to halt it at any stage.

The nucleation and initial growth of Fe on the (1 × 1) rutile TiO 2 (110) substrate as a function of coverage and annealing temperature were studied using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The deposition of 0.03 ML–0.3 ML (monolayer) of Fe resulted in the growth of one-, two- and three-dimensional iron clusters. Surface annealing at 373 K and 473 K resulted in a moderate sintering of the Fe clusters, whereas annealing at higher temperatures led to Fe incorporation into the substrate. The analysis of the Fe 2p core excitations showed that even after room temperature processes, iron was partially oxidized at the iron/titania interface.

Fe/MgO/Fe trilayers with a subnanometer MgO tunnel barrier were grown by molecular beam epitaxy. Longitudinal magnetooptic Kerr effect measurements confirmed the existence of the antiferromagnetic interlayer exchange coupling (IEC) between the Fe layers for 2 A

Our aim was to study the influence of low doses (0.2-4 μGy) of α radiation on the stability of human erythrocytes isolated from healthy and diabetic erythrocytes. Absorption spectroscopy was used to measure the level of red blood cell (RBC) hemolysis, along with Mossbauer spectroscopy, which is a highly specific method suited to monitoring various hemoglobin forms. States of hemoglobin are sensitive to a homeostatic imbalance in red blood cells. Changes in the membrane skeleton organization of irradiated erythrocytes isolated from healthy donors were studied using atomic force microscopy (AFM). Hemolysis, in healthy red blood cells, showed characteristic discontinuities, depending on the α particle flux and the exposure time to the low doses applied. This phenomenon was not observed in severe diabetic cases, which could be a result of modified protein-lipid-sugar complexes and the attenuation/absence of some antioxidative enzymatic processes in their RBC membranes. Similar effects were also observed for red blood cells treated with low doses of neutron and γ-radiation. AFM measurements demonstrated a reorganization of the RBC membrane skeleton network depending on the time of RBC exposure to α radiation. This suggests that the changes in the activity of the acute defense processes against free radicals which are activated within the erythrocyte membrane irradiated with α-particles could additionally be up- or down regulated by modifications to the membrane-skeleton network. However, even the highest dose of α radiation applied in these studies did not cause any significant changes in the ability of hemoglobin to transport oxygen. Microsc. Res. Tech. 80:131-143, 2017. © 2016 Wiley Periodicals, Inc.

Adsorption of oxygen on the (110) surface of epitaxial iron films on tungsten (110) was studied using low-energy electron diffraction (LEED), low-energy electron microscopy (LEEM), and Auger electron spectroscopy within an exposure range of 0–300 Langmuir (L). Selected oxygen adsorption structures on Fe(110) reported in the literature were critically compared and revised in reference to the present study. The initial adsorption of 1/4 oxygen monolayer resulting in the commonly observed (2 × 2) structure was followed by a structure that was frequently termed as (3 × 1). Its complex LEED pattern was ultimately resolved and interpreted as originating from two structural domains of a large oblique unit cell (eight times larger than the substrate unit cell) and 3/8 oxygen coverage. A new (3 × 2) structure was identified at a coverage of 2/3. The domain interpretation of last two structures was verified by LEEM and confirmed by density functional theory calculations. The onset of oxygen–iron bonding formation w...

Systematic studies of the two high-temperature monolayer oxygen structures that exist on the (110) tungsten surface were performed using low-energy electron microscopy and diffraction measurements. Our work questions the commonly accepted interpretation from the literature that striped oxygen superstructures arise from alternating site-exchanged (S-E) domains. We postulate that the superstructures originate from a misfit between tungsten and oxygen lattices while the striped appearance corresponds to a moire pattern. Moreover, we show that the two structures, indicated as 113- and 337-phases due to the characteristic directions of the respective moire patterns, differ considerably in their symmetry properties. This suggests that oxygen atoms in the two overlayers occupy different adsorption sites on average. In particular, the 113-phase features rotational domains that retain mirror symmetries with respect to the [ 001 ] and [ 1 1 ¯ 0 ] directions, whereas the 337-phase is characterized by the appearance of additional domains due to the breaking of these symmetries. We propose structural models for both phases that consistently explain their unusual properties and suggest a universal mechanism for the thermal evolution of oxygen monolayer adsorbed on W(110).

We present studies on CO adsorption on an Fe3O4(1 1 1) surface with a regular tetrahedral termination (Fetet1) and with different hexagonal superstructures called ‘biphase’ structures. All these terminations were precisely controlled on a 70 A magnetite layer epitaxially grown on a Pt(1 1 1) single crystal. The experiments, including low energy electron diffraction, scanning tunnelling microscopy (STM) and temperature-programmed desorption (TPD), were carried out in situ under ultrahigh vacuum conditions. During the TPD measurements, the Fe3O4(1 1 1) surfaces were exposed to 0.1–20 L of CO at 105 K, and then the samples were heated with a linear temperature rise to 600 K. We found that as the Fetet1-terminated area decreases, as confirmed by STM observations, the surface becomes less active in CO adsorption. This means there are fewer adsorption states on the biphase structure than on Fe3O4(1 1 1) with regular termination.

We report on the large coercivity enhancement in epitaxial Fe/FeRh bilayer grown on W(110). It is shown that the coercive field increases by almost an order of magnitude when the FeRh alloy undergoes a phase transition from the ferromagnetic to antiferromagnetic state. Analysis of temperature spin structure evolution of the FeRh alloy across the magnetic transition reveals that the observed coercivity enhancement is caused by the interfacial spin-flop coupling between Fe and the antiferromagnetic FeRh layer.

We report on the in-plane magnetic anisotropy in Au/Fe(1 1 0) and Co/Au/Fe(1 1 0) bi- and trilayers epitaxially grown on a W(1 1 0) single crystal. Magnetic surface anisotropy (MSA) exhibits a strongly non-monotonic, oscillatory behavior as a function of Au thickness. In the case of the Au/Fe(1 1 0) bilayers bi-periodic oscillations were observed and interpreted in terms of quantum well states that are affected by the alternating complete and in-complete atomic layers of Au. Thin bcc Co films grown on Au/Fe(1 1 0) bilayers strongly enhance MSA and for the Co/Au/Fe system magnetic anisotropy oscillates as a function of the Au spacer thickness due to the oscillatory interlayer coupling.

We studied the magnetic properties of 10 and 20 nm-thick, gold-capped FeRh layers grown on MgO(0 0 1). Whereas the majority of the FeRh film undergoes ferromagnetic–antiferromagnetic phase transition upon cooling, a small fraction of the FeRh system remains in the ferromagnetic state at low temperatures. This residual ferromagnetic phase located at the FeRh/MgO interface exhibits perpendicular magnetic anisotropy. Moreover, in the 10 nm-thick film, a small amount of the antiferromagnetic phase survives to high temperatures above the phase transition and probably originates from the epitaxial strains generated at the FeRh/Au interface.

Antiferromagnet/ferromagnet (AFM/FM) bilayers that display the exchange bias (EB) effect have been subjected to intensive material research, being the key elements of novel spintronics systems. In a commonly accepted picture, the antiferromagnet, considered as a rigid material due to its high anisotropy and magnetic hardness, controls the magnetic properties of the ferromagnet, such as a shift of the hysteresis loop or coercivity. We show that this AFM-FM master-slave hierarchy is not generally valid and that the influence of the ferromagnet on the magnetic anisotropy (MA) of the neighbouring antiferromagnet must be considered. Our computer simulation and experimental studies of EB in an epitaxial CoO/Fe(110) bilayer show that the ferromagnetic layer with strong uniaxial magnetic anisotropy determines the interfacial spin orientations of the neighbouring AFM layer and rotates its easy axis. This effect has a strong feedback on the EB effect experienced by the FM layer. Our results show new physics behind the EB effect, providing a route for grafting a desired anisotropy onto the AFM and for precise tailoring of EB in AFM/FM systems.

Acireductone dioxygenase (ARD) is an intriguing enzyme from the methionine salvage pathway that is capable of catalysing two different oxidation reactions with the same substrate depending on the type of the metal ion in the active site. To date, the structural information regarding the ARD–acireductone complex is limited and possible reaction mechanisms are still under debate. The results of joint experimental and computational studies undertaken to advance knowledge about ARD are reported. The crystal structure of an ARD from Homo sapiens was determined with selenomethionine. EPR spectroscopy suggested that binding acireductone triggers one protein residue to dissociate from Fe(2+), which allows NO (and presumably O(2)) to bind directly to the metal. Mössbauer spectroscopic data (interpreted with the aid of DFT calculations) was consistent with bidentate binding of acireductone to Fe(2+) and concomitant dissociation of His88 from the metal. Major features of Fe vibrational spectra obtained for the native enzyme and upon addition of acireductone were reproduced by QM/MM calculations for the proposed models. A computational (QM/MM) study of the reaction mechanisms suggests that Fe(2+) promotes O—O bond homolysis, which elicits cleavage of the C1—C2 bond of the substrate. Higher M(3+) /M(2+) redox potentials of other divalent metals do not support this pathway, and instead the reaction proceeds similarly to the key reaction step in the quercetin 2,3-dioxygenase mechanism.

The synchrotron radiation facility ‘Solaris’ is currently being built in Krakow, Poland. The first experimental beamline at Solaris will use bending magnet radiation and two exchangeable end stations: a spectroscopic X-ray photoemission electron microscope and a soft X-ray absorption spectroscopy chamber. We present the beamline specifications and exemplary results obtained with our end station microscope, which (in statu nascendi of Solaris) has been operated at the NanoXAS beamline in the Swiss Light Source. The end stations should be available for a broad user community at Solaris in 2016. Copyright © 2015 John Wiley & Sons, Ltd.

The synthesis and characterization of porphyrazines possessing 2,5–diphenylpyrrol-1-yl and dimethylamino peripheral groups and their precursors are shown. Bulky pyrrolyl substituents influenced the physicochemical properties and solid-state structure of novel porphyrazines and did not hamper the formation of the porphyrazine associates in solution and solid-state. Occurrence of centrosymmetric dimers in single crystal X-ray structure of magnesium(II) porphyrazine with Mg⋯Mg distance of ca. 11.2 A, impacted by interdigitation of the phenyl substituents, was noticed. In addition, an iron(II) porphyrazine derivative was investigated. The importance of Mossbauer spectroscopy in the assessment of valence and spin state of the iron ion inside the core of the iron(II) porphyrazine is shown.

Controlling spin orientation in magnetic nanostructures is one of the crucial issues in modern spintronics. The authors show a mechanism for steering the spin direction of a ferromagnet that is coupled to FeRh alloy. In Co/FeRh epitaxial bilayers, when the FeRh undergoes its antiferromagnetic-to-ferromagnetic transition, spins in the Co film reversibly switch between orthogonal in-plane directions. This phenomenon, which goes beyond the popular idea of heat-assisted magnetic recording (HAMR), provides a means of writing information $p\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ by a temperature change, which could be due to localized laser illumination, for example.

We report results of first-principles study of the adsorption of atomic oxygen and magnesium on the Fe(001) surface. Two adsorption scenarios were considered. In the first process, the Mg atoms were adsorbed on the Fe(001) surface with preadsorbed O atoms, whereas in the second scenario metallic Mg preadsorbed on the Fe(001) surface was exposed to oxygen. For both O and Mg atoms, fourfold hollow sites were found as the energetically most favorable adsorption sites on the clean Fe(001) surface. The result of both adsorption scenarios was the formation of a MgO adlayer on the Fe(001) surface with a sharp MgO/Fe interface. In particular, the deposition of Mg atoms on O/Fe(001) showed that magnesium can pull out O adatoms from the Fe surface. Structural, electronic, and magnetic properties were analyzed as a function of O and Mg coverages. The calculated electronic structure and magnetic moments showed that the full MgO monolayer affects the properties of the Fe surface much weaker than an incomplete MgO adsorbate layer.

Fe

The morphology of Au films on W(1 1 0) was studied as a function of the Au thickness by scanning tunnelling microscopy and low-energy electron diffraction. The stress originating at the fcc-Au/bcc-W interface was found to significantly affect the directionality of the reconstruction by favouring one particular rotational domain of the well-known Au herringbone pattern. The presence of characteristic defect bunches, interpreted to be edge dislocation loops, also contributed to the disturbances in the reconstruction pattern. The observed defects were strictly correlated with the dimensions of the structural domains of the reconstruction. To examine nucleation processes on an anisotropically reconstructed surface, the Au films were used as an adsorption template for Ag. On the hcp stacking regions of the reconstruction Ag showed a tendency to form nanowires.

The relation between the interface structure and the exchange bias was studied in the epitaxial CoO/Fe(0 0 1) bilayers that were grown on MgO(0 0 1) using molecular beam epitaxy. Three samples with different interface structures were prepared. The CoO/Fe bilayer, which was prepared using the reactive evaporation of CoO, served as the reference sample. In the other two samples, the CoO/Fe interfaces were modified prior to the CoO growth using either (i) the deposition of a 2 A thick Co layer or (ii) an exposure to molecular oxygen, which resulted in under- and over-oxidized CoO/Fe interfaces, respectively. The actual structures of the resulting interfaces were revealed using conversion electron Mossbauer spectroscopy. For each sample, an iron oxide was found at the interface, and its amount depended on the sample preparation recipe. The exchange bias effect (EB), as a function of the temperature, was experimentally studied in detail using VSM magnetometry. The coercivity showed a distinct peak near the blocking temperature for all samples; however, the peak's location and its width were diverse. The obtained EB values depended on the interface structure. The largest hysteresis loop shift (HEB = 180 Oe at 4 K) was obtained for the sample with the thickest interfacial iron oxide layer.

20 nm manganese films were deposited on a MgO(001) substrate by the molecular beam epitaxy under ultrahigh vacuum conditions. The films were characterized in situ by low energy electron diffraction (LEED), electron spectroscopies and scanning tunneling microscopy (STM) and ex situ by X-ray diffraction (XRD). During the deposition the substrate was kept at room temperature. The as-deposited films did not show any distinct LEED pattern, which emerged only upon in situ annealing at 423 K, and further improved upon subsequent annealing steps at temperatures up to 623 K. The LEED pattern indicated a square surface unit cell that is commensurate with the MgO(001) substrate. STM images showed island growth of the films. The islands exposed atomically flat terraces extending approximately over 500 A. The XRD analysis confirmed a single phase α-Mn film structure with the (001) orientation, rotated in plane by 45° relative to the MgO(001) lattice.

Depending on the preparation recipe the Fe3O4(001) surface of epitaxial magnetite films on MgO(001) can be stabilized as an oxygen-rich or iron-rich surface. The present study reports the adsorption of gold in a coverage range from submonolayers to several monolayers on the Fe-rich Fe3O4(001) surface with the (√2 × √2)R45° reconstruction, which is terminated by Fe dimers. The surface atomic structure was refined and interpreted based on the atomically resolved scanning tunneling microscopy (STM) images. For submonolayer coverage, single Au atoms were found to be stable at room temperature, and from the STM analysis, the atomic Au adsorption sites were identified at the Fe dimers. Eventually, for the multilayer films, the Au adsorbate follows an epitaxial layer-by-layer growth, and the resulting Au films expose the (111) face.

Recently, perpendicular magnetic anisotropy (PMA) and its voltage control (VC) was demonstrated for Cr/Fe/MgO. In this study, we shed light on the origin of large voltage-induced anisotropy change in Cr/Fe/MgO. Analysis of the chemical structure of Cr/Fe/MgO revealed the existence of Cr atoms in the proximity of the Fe/MgO interface, which can affect both magnetic anisotropy (MA) and its VC. We showed that PMA and its VC can be enhanced by controlled Cr doping at the Fe/MgO interface. For Cr/Fe (5.9 Å)/Cr (0.7 Å)/MgO with an effective PMA of 0.8 MJ/m3, a maximum value of the voltage-controlled magnetic anisotropy (VCMA) effect of 370 fJ/Vm was demonstrated due to Cr insertion.

In our study, we examined the chemical and magnetic properties of FeO in an epitaxial Fe/MgO(dMgO)/FeO trilayer for different MgO thicknesses, dMgO. Analysis of the chemical structure revealed a stoichiometry improvement in the FeO layer in Fe/MgO/FeO in comparison with a Fe/FeO bilayer. Furthermore, we showed that deposition of a subtle MgO layer at the Fe/FeO interface results in an enhanced exchange interaction between Fe and FeO. For dMgO = 1.4 A, we noted a 200% enhancement in the exchange bias in Fe/MgO/FeO compared to that in Fe/FeO.

We investigated Fe-phases of iron complexes embedded in nonfunctionalized (as-prepared) and functionalized multi-wall carbon nanotubes (MWCNTs). Mossbauer spectroscopy is a very sensitive tool to study chemical states of iron compounds embedded in MWCNTs. It showed that the chemical treatment of the as-prepared MWCNTs caused release of about 84% of iron and modification of the remaining iron compounds. In as-prepared and carboxylated MWCNTs almost 80 and 75% of iron complexes in a form of Fe3C exhibited magnetic ordering even at room temperature, respectively. In MWCNT-COONH4 only 50% of such iron compounds showed local magnetic ordering. In all cases about 2% of magnetic α-Fe fraction was detected. Through the dc magnetization and transmission electron microscopy (TEM) measurements it was proved that cementite nanoparticles formed agglomerates and their sizes were larger than 10 nm. STM measurements indicated increased homogeneity of the surface electric properties in the case of chemically treated carbon nanotubes.

The near-surface structural properties of epitaxial Fe(1 1 0) films on W(1 1 0) were studied using quantitative low-energy electron diffraction analysis. A discernible, up to 1%, relaxation of the outermost atomic layers was found, in contrast to the bulk Fe(1 1 0) surface, which shows almost no relaxation.

The thickness- and temperature-induced in-plane spin reorientation transitions (SRT) in epitaxial Fe films on a W(110) single crystal were investigated using X-ray photoemission electron microscopy. We present the real time evolution of the magnetisation switching, and we demonstrate differences between the two transition mechanisms. Whereas both the transitions involve the magnetic domain wall motion, the temperature SRT is additionally accompanied by nucleation of domains. Before and after the thickness-induced SRTs, the sample is in the almost single domain state, which is not the case for the final magnetic configuration after the temperature-induced transition.

Our aim was to study the influence of low doses (0.2-4 μGy) of α radiation on the stability of human erythrocytes isolated from healthy and diabetic erythrocytes. Absorption spectroscopy was used to measure the level of red blood cell (RBC) hemolysis, along with Mössbauer spectroscopy, which is a highly specific method suited to monitoring various hemoglobin forms. States of hemoglobin are sensitive to a homeostatic imbalance in red blood cells. Changes in the membrane skeleton organization of irradiated erythrocytes isolated from healthy donors were studied using atomic force microscopy (AFM). Hemolysis, in healthy red blood cells, showed characteristic discontinuities, depending on the α particle flux and the exposure time to the low doses applied. This phenomenon was not observed in severe diabetic cases, which could be a result of modified protein-lipid-sugar complexes and the attenuation/absence of some antioxidative enzymatic processes in their RBC membranes. Similar effects were also observed for red blood cells treated with low doses of neutron and γ-radiation. AFM measurements demonstrated a reorganization of the RBC membrane skeleton network depending on the time of RBC exposure to α radiation. This suggests that the changes in the activity of the acute defense processes against free radicals which are activated within the erythrocyte membrane irradiated with α-particles could additionally be up- or down regulated by modifications to the membrane-skeleton network. However, even the highest dose of α radiation applied in these studies did not cause any significant changes in the ability of hemoglobin to transport oxygen. Microsc. Res. Tech. 80:131-143, 2017. © 2016 Wiley Periodicals, Inc.

We report on in-plane magnetic anisotropy in epitaxial bcc Co/Fe(110) bilayers on W(110). The magnetic surface anisotropy in the Co/Fe(110) bilayers exhibited a strong nonmonotonic dependence on Co coverage. Magneto-optical studies revealed a sharp maximum of the magnetic surface anisotropy, $2.44\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}/{\mathrm{m}}^{2}$, at ${d}_{\mathrm{Co}}=5\phantom{\rule{0.16em}{0ex}}\AA{}$. This giant interfacial magnetic anisotropy allowed a small fraction of a Co monolayer to reorient the magnetization of the bulk-like Fe film. We conclude that the mono- and double-layer bcc Co(110) exhibited in-plane magnetic anisotropy with a $[1\overline{1}0]$ easy axis.

a b s t r a c t Au/FeOx catalysts were prepared by deposition of Au on Fe3O4 (commercial Cerac, a mixture of magnetite and maghemite) with the deposition-precipitation method, and heating of the precursors in air or in Ar. The catalysts were characterized by XPS, Mossbauer spectroscopies, H2TPR, TEM, decomposition of isopropanol (probe reaction for acid-base properties), and tested in CO oxidation. The heating atmosphere influences composition, physicochemical and catalytic properties. The cata- lysts prepared in Ar contain magnetite, MT and maghemite, MG as the main iron oxide phases, for those calcined in air MG is the only phase observed. Higher amounts of weakly bound oxygen are observed in H2TPR measurements for the catalysts prepared in air. They exhibit smaller acidity and higher basicity compared to the samples prepared in Ar. The mean particle size of nano Au is not affected markedly by the preparation conditions and amounts to ∼4.5 nm. Calcination in Ar appears, however, to stabilize smaller particles (