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Adsorption of gases on the surface of all-bcc (Fe/Co)N superlattices drives the in-plane, 90° magnetization rotation of the bulk-like Fe(110) supporting ferromagnet. Both experimental and theoretical results prove that terminating the surface of (Fe/Co)N superlattices either by Co or by Fe switches “ON” or “OFF” the spin orientation sensitivity to adsorption. Results indicate that purely surface limited adsorption processes strongly modify the magnetic anisotropy of the entire (Fe/Co)N superlattice, which acts as a kind of “artificial” surface of the bulky Fe(110) ferromagnet. Such an artificial magnetic surface anisotropy concept not only enhances the surface contribution in classical surface–bulk competition but also provides its additional chemical sensitivity.

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.

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.

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.

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.

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.

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.

We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (Q_A-Fe-Q_B) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron–quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Mössbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Mössbauer measurements show that the hydrophobicity of the Q_A binding site can be crucial for stabilization of the high spin ferrous state of NHFe.

Different forms of iron compounds embedded in non-functionalized (as prepared) and functionalized multiwall carbon nanotubes (MWCNTs) were studied. Iron used to catalyze MWCNT synthesis can be found inside nanotubes and built-in within their walls. Mossbauer spectroscopy was applied to study valence and spin states as well as magnetic ordering of the iron compounds. In the Mossbauer spectra of as prepared MWCNTs the Fe3C carbide provides the main contribution. The content of Fe3C decreases by about 20 and 40% in carboxylated carbon nanotubes (MWCNTs-COOH) and ammonium salt of carboxylated carbon nanotubes (MWCNTs-COONH4), respectively. A small amount of α-Fe and FexCx iron forms are always observed in all studied carbon nanotubes. In MWCNTs-COOH, additionally, ferrihydrates and/or FexCy with oxygen in the second coordination sphere of iron are present (at a level of about 17%). In MWCNTs-COONH4 their content increases by a factor of 3. The experimental data shows that the purification and functionalization of as prepared MWCNTs result in removal of about 90% of iron contaminations. Additionally, we observe the modification of iron compounds inside MWCNTs. All these results are important in optimizing the as prepared MWCNT purification process and in finding a new way to produce different Fe phases inside MWCNTs.

The potential applications of carbon nanotubes (CNTs) are strongly related to their physical and chemical properties. In this work, results of different methods for the oxidation of crude CNTs are reported. These methods changed Fe binding sites within multiwall carbon nanotubes (MWCNTs). Mossbauer spectroscopy was used to detect the chemical properties of the Fe-phases in MWCNTs. Signals from the iron carbide Fe3C were the main components in the Mossbauer spectra of unmodified MWCNTs revealing magnetic ordering even at 300 K. In oxidized MWCNTs, the amount of Fe3C decreased and γ-Fe and α-Fe, ferrihydrates of iron oxides and different forms of goethite appeared. In MWCNTs oxidized with HClO4, a significant fraction (∼24%) of magnetically ordered Fe2O3 particles was detected. This study showed that traces of iron catalyst embedded in MWCNTs could be used as a sensitive probe to monitor various MWCNT modifications.

We demonstrate that FeRh layers can be implemented to the epitaxial Fe/Au/FeRh spin valve structures grown on MgO(001). Owing to the AFM-FM phase transition in the FeRh film, the magnetic structure of our Fe/Au/FeRh system can be temperature controlled. The indirect exchange coupling between Fe and FeRh films mediated by the Au spacer enables to control the relative orientation of the Fe and FeRh magnetizations by the Au spacer thickness between ferromagnetic and non-collinear with nearly orthogonal magnetizations. Moreover, the evolution of magnetic structure of the Fe/Au/FeRh system along with the AFM-FM transition is accompanied by the reversible in-plane rotation of the top Fe-layer magnetization.We demonstrate that FeRh layers can be implemented to the epitaxial Fe/Au/FeRh spin valve structures grown on MgO(001). Owing to the AFM-FM phase transition in the FeRh film, the magnetic structure of our Fe/Au/FeRh system can be temperature controlled. The indirect exchange coupling between Fe and FeRh films mediated by the Au spacer enables to control the relative orientation of the Fe and FeRh magnetizations by the Au spacer thickness between ferromagnetic and non-collinear with nearly orthogonal magnetizations. Moreover, the evolution of magnetic structure of the Fe/Au/FeRh system along with the AFM-FM transition is accompanied by the reversible in-plane rotation of the top Fe-layer magnetization.

A study of in-plane magnetic anisotropy (MA) in epitaxial bcc Co films and Fe/Co bilayers on a Fe(110) surface is reported. Surface MA of as-deposited Co films and Fe/Co bilayers strongly depends on the Co (dCo) and Fe (dFe) thickness. Adsorption of residual gases drastically modifies in-plane MA of both Co films and Fe/Co bilayers. We present two dimensional MA maps in the (dCo, dFe) space for both as grown and adsorption-modified films. Our results indicate how to precisely engineer in-plane MA that can be controlled by dCo, dFe and is sensitive to the residual gas adsorption.

The initial growth and influence of annealing on structural and magnetic properties of 5 monolayers epitaxial Fe films on cleaved and polished MgO(0 0 1) substrates was studied using conversion electron Mossbauer spectroscopy (CEMS). Broadening of LEED spots indi- cated a granular structure of the films grown at room temperature. The CEMS analysis showed that the film on the cleaved substrate is flat and consists of a 2 ML interfacial layer with the electronic structure affected by the oxidic substrate, while the remaining 3 ML are metallic with the Curie temperature below RT. Annealing changes the film structure, as seen by CEMS, but only for temperatures above 550 K. In the annealing process the continuous film breaks into 3-dimensional islands and oxidation takes place at the Fe/cleaved-MgO interface. On the polished substrate, the as-prepared film consists of small superparamagnetic metallic iron particles. Contrary to the cleaved substrate, no oxidation is observed at the interface upon annealing. � 2007 Elsevier B.V. All rights reserved.

We investigated changes in the magnetic properties of a single Fe monolayer on Au(0 0 1) induced by the interlayer exchange coupling (IEC) to FeAu monoatomic superlattices. The grazing incidence nuclear resonant scattering of X-rays (GI-NRS) combined with the 57 Fe probe layer concept allowed us to selectively monitor the local structure and magnetism of the Fe(0 0 1) monolayer in a coupled state. The dependence of the monolayer hyperfine parameters on temperature and spacer thickness was determined from the fitted GI-NRS time spectra, collected for the selected thickness of the stepped Au spacer. The influence of the coupling on the hyperfine magnetic field B HF was negligible at temperatures much lower than T C of the uncoupled Fe monolayer ( T C = 210 K as checked by MOKE). The analysis of the time-spectra accumulated at 200 K showed a non-monotonous dependence of the average B HF as a function of the spacer thickness, related to IEC oscillations. The maximum influence of IEC on B HF (13 T) was found for the 4 ML Au spacer.

Metal-oxide ${\mathrm{[Fe}}_{K}/(\text{MgO}){}_{L}{\mathrm{]}}_{N}$ multilayers were grown on MgO(001) substrates for various integer numbers $(K,L)$ of the Fe(001) and MgO(001) monolayers, respectively, and the number of repetitions $N$ varied from 6 to 30. Room-temperature conversion electron M\"ossbauer spectroscopy (CEMS) measurements proved that the magnetic properties of these monoatomic multilayers were extremely sensitive to both the Fe and MgO sublayer thicknesses. A stable ferromagnetic state and a strong perpendicular magnetization component at room temperature were obtained by changing the sublayer thickness and the number of multilayer repetitions. The analysis of the CEMS spectra in correlation with the magneto-optic Kerr effect measurements indicated a complicated domain structure in this special type of metal-insulator material. The vortexlike domain structure was confirmed by micromagnetic simulations.

Exchange bias (EB) is studied in an epitaxial CoO/Fe bilayer grown by molecular beam epitaxy on MgO(001). The characterization of the layer structure and interface quality was performed using LEED, AES and conversion electron Mossbauer spectroscopy(CEMS). Detailed experimental studies of the EB effect as a function of temperature were carried out using the magneto-optical Kerr effect. Notwithstanding the formation of Fe oxides at the CoO/Fe interface, as evidenced by the CEMS measurements, we observed a negative EB with blocking temperature T B = 257 K. At temperatures close to T B , the coercive field reaches a maximum, which is in agreement with the stiles and McMichael model.

We investigated the spin reorientation transition during the growth of Fe(110) films on W(110) at 250 \ifmmode^\circ\else\textdegree\fi{}C using the in situ nuclear resonant scattering of x rays. The measurements as a function of the grazing incidence angle demonstrated that the spin reorientation proceeds via an intermediate, noncollinear magnetic state, and with increasing thickness, the magnetization reorientation from the [1$\overline{1}$0] to the [001] direction is activated at the film surface and completed at the Fe/W interface. Furthermore, as the temperature was decreased from 250 \ifmmode^\circ\else\textdegree\fi{}C to 160 \ifmmode^\circ\else\textdegree\fi{}C, the temperature-driven spin reorientation transition (SRT) between the [001] and [1$\overline{1}$0] directions was observed with a similar noncollinear transient magnetic state. The thickness-temperature SRT phase diagram was schematically drawn.

We studied radiation effects on the stability of various states of hemoglobin (Hb) in red blood cells (RBC) irradiated with a very low dose of neutron rays, 50 μGy. We investigated RBCs isolated from blood of healthy donors. Mossbauer spectroscopy was applied to monitor different forms of Hb. Our results show, for the first time, that oxyhemoglobin (OxyHb) and deoxyhemoglobin (DeoxyHb) are two Hb forms sensitive to such a low neutron radiation. Both Hbs change into a new Hb form (Hbirr). Additionally, OxyHb transfers into HbOH/H2O, which under our experimental conditions is resistant to the action of neutron rays.

We investigate the dynamical properties of the non-heme iron (NHFe) in His-tagged photosynthetic bacterial reaction centers (RCs) isolated from Rhodobacter (Rb.) sphaeroides. Mössbauer spectroscopy and nuclear inelastic scattering of synchrotron radiation (NIS) were applied to monitor the arrangement and flexibility of the NHFe binding site. In His-tagged RCs, NHFe was stabilized only in a high spin ferrous state. Its hyperfine parameters (IS=1.06±0.01mm/s and QS=2.12±0.01mm/s), and Debye temperature (θD0~167K) are comparable to those detected for the high spin state of NHFe in non-His-tagged RCs. For the first time, pure vibrational modes characteristic of NHFe in a high spin ferrous state are revealed. The vibrational density of states (DOS) shows some maxima between 22 and 33meV, 33 and 42meV, and 53 and 60meV and a very sharp one at 44.5meV. In addition, we observe a large contribution of vibrational modes at low energies. This iron atom is directly connected to the protein matrix via all its ligands, and it is therefore extremely sensitive to the collective motions of the RC protein core. A comparison of the DOS spectra of His-tagged and non-His-tagged RCs from Rb. sphaeroides shows that in the latter case the spectrum was overlapped by the vibrations of the heme iron of residual cytochrome c2, and a low spin state of NHFe in addition to its high spin one. This enabled us to pin-point vibrations characteristic for the low spin state of NHFe.

An in-plane spin-reorientation transition occurring during the growth of epitaxial Fe films on W(110) was studied in situ by using the nuclear resonant scattering of synchrotron radiation. The spin-reorientation transition originates at the Fe/W(110) interface and proceeds via a noncollinear spin structure resembling a planar domain wall that propagates towards the surface with increasing film thickness.

The magnetic properties of ultrathin Fe films grown on Au(001) were studied at room temperature as a function of iron thickness in the range of two to three Fe monolayers (ML). The magneto-optic Kerr effect (MOKE) indicated that a spin reorientation from an in-plane direction to the film normal direction takes place when the iron thickness is reduced from 2.3 to 2.0 ML. Values of the effective magnetic anisotropy constants were determined from MOKE and superconducting quantum interference device measurements. The flow analysis of the effective anisotropy constants in anisotropy space revealed that the transition occurs via an intermediate state of canted magnetization.

We have engineered the magnetic properties of 1-8 nm Co films epitaxially grown on an Au-buffered bifacial W(110)/W(540) single crystal. The surface of Au/W(110) was atomically flat, whereas the Au/W(540) followed the morphology of the vicinal W surface, showing a regular array of monoatomic steps. For Co grown on Au/W(540), the existence of the out-of-plane magnetization component extended strongly to a thickness d of about 8 nm, which was accompanied by an anomalous increase of the out-of-plane switching field with increasing d. In addition, the process of up-down magnetization switching could be realized with both a perpendicular and in-plane external magnetic field.

Comparative studies of the magnetic properties of epitaxial Fe/MgO/Fe trilayers, which were directly grown on an MgO(001) crystal and a homoepitaxial MgO buffer layer, were performed to examine the interlayer exchange coupling as a function of the MgO spacer thickness. Measurements of the magneto-optic Kerr effect at room temperature demonstrated that there was a strong antiferromagnetic coupling (AFC) between the Fe layers, which was mediated by the insulating MgO barrier. A measurable AFC was found in a range of MgO thickness (dMgO) from a single monolayer (2 A) to 6 A, which had a maximum strength of −1.15 ergs/cm2 at dMgO = 2.7 A for the Fe/MgO/Fe trilayers that were prepared on the buffered sample and was notably weaker for the trilayers that were prepared directly on the MgO(001).

Nuclear resonant scattering (NRS) of synchrotron radiation was used to investigate the magnetic anisotropy of iron films in MgO/Fe(t)/MgO(001) structures for t = (4–10) A. The low-temperature NRS spectra were analyzed using a static magnetization model involving two interface-like components and a bulk-like component. We confirmed the existence of perpendicular magnetic anisotropy in MgO/Fe/MgO structures at 10 K with an increasing in-plane component of the magnetization for t > 8 A over the entire thickness of the Fe film. The evolution of the magnetic structure with increasing temperature was studied for an Fe film thickness of 8.8 A, and the temperature dependence of superparamagnetic fluctuations with characteristic frequencies ranging over tens of MHz was interpreted in terms of a spin reorientation transition. We showed that interfacial magnetic moments are less sensitive to thermal excitations than the magnetic moments in the film center, which was attributed to the spin pinning at the interface.

Non-heme Fe is a conservative component of the Q-type photosynthetic reaction centers but its function remains unknown. Applying Mossbauer spectroscopy we show that in Rhodospirillum rubrum the non-heme Fe exists mostly in a ferrous low spin state. The binding of Cd2+ ions in the vicinity of the quinone-Fe complex changes the high spin state of the non-heme Fe into a low spin one characterized by hyperfine parameters similar to those obtained for the non-heme Fe low spin state in untreated reaction centers, as confirmed by Mossbauer measurements. The nuclear inelastic scattering of synchrotron radiation experiments show that the contribution of vibrations at low energies, between 3-15 meV, activated at 240 K are damped in the bacterial reaction centers treated with CdCl2. No influence of Cd2+ ions is observed on the soft vibrational states at 60 K. These results suggest that binding of cadmium cations within the reaction centers may enhance decoupling of the non-heme Fe from the surrounding protein matrix at temperatures higher than 200 K, what can explain the slowing down of electron transfer between the QA and QB quinones by Cd2+.

Conversion electron Mossbauer spectroscopy proved in the past to be very useful in studying surface and ultrathin film magnetism with monolayer resolution. Twenty years later, its time-domain analogue, the nuclear resonant scattering (NRS) of synchrotron radiation, showed up to be by orders of magnitude faster and more efficient. The evolution of the spin structure in epitaxial 57Fe films on a tungsten W(110) was studied via the accumulation of the NRS time spectra directly during Fe film deposition. In the 0.5 – 4 monolayers Fe thickness range, the complex non-collinear magnetic structure was derived from the NRS data, resulting from the deviation from the layer by layer growth mode. For thicker Fe films, the in-plane thickness induced spin reorientation transition could be clearly identified. Based on the NRS analysis it is shown that SRT process originates at the Fe/W(110) interface and proceeds through a transient fan-like magnetization structure.

We studied magnetization reversal processes and magnetic anisotropy in ultrathin Au∕Co∕Au films deposited on a bifacial Mo(110)/(540) single crystal. The influence of the Co thickness and miscut angle on the spin reorientation from out-of-plane into in-plane magnetization were investigated by means of the magneto-optical Kerr effect (MOKE). In the case of Co grown on a vicinal Au∕Mo(540) substrate, the perpendicular magnetization component was found throughout the 1–8nm Co thickness range. The canted orientation of magnetization was deduced from vectorial MOKE magnetometry. The out-of-plane switching field, which is 160Oe for the perpendicular magnetization, increases to about 960Oe as observed at 8nm Co thickness on the vicinal part. The experimental data are discussed taking into account both uniaxial out-of-plane and in-plane magnetic anisotropy energy terms. The results indicate the possibility of tuning the perpendicular magnetization component with the use of vicinal substrates, and are important fr...

In der vorliegenden Arbeit wird uber die in der Literatur bisher noch unbekannten IR-Spektren von Wasser-Methanol-Mischungen sowie von Magnesiumsulfatlosungen in diesen Losungsmittelmischungen berichtet. Es wurde der Einflus von Salzzugaben auf die Lage sowie die Intensitat der Absorptionsmaxima von Wasser und Methanol untersucht. Die dabei auftretenden Veranderungen werden mit den in den untersuchten Systemen vorhandenen Wechselwirkungen in Verbindung gebracht. Spectroscopic Studies on Water-Methanol Solutions of Magnesium Sulphate in Near Infrared Region Spectroscopic studies on spectra of water-methanol solutions and water-methanol solutions of magnesium sulphate, unknown in literature, are presented. The influence of salt addition on the position of absorption maxima of water and methanol, as well as their intensity, was observed. The changes described were connected with interaction existing in tested systems.

Non-heme iron is a conservative component of type II photosynthetic reaction centers of unknown function. We found that in the reaction center from Rba. sphaeroides it exists in two forms, high and low spin ferrous states, whereas in Rsp. rubrum mostly in a low spin state, in line with our earlier finding of its low spin state in the algal photosystem II reaction center (Burda et al., 2003). The temperature dependence of the non-heme iron displacement studied by Mossbauer spectroscopy shows that the surrounding of the high spin iron is more flexible (Debye temperature ~ 165 K) than that of the low spin atom (~ 207 K). Nuclear inelastic scattering measurements of the collective motions in the Rba. sphaeroides reaction center show that the density of vibrational states, originating from non-heme iron, has well-separated modes between lower (4–17 meV) and higher (17–25 meV) energies while in the one from Rsp. rubrum its distribution is more uniform with only little contribution of low energy (~ 6 meV) vibrations. It is the first experimental evidence that the fluctuations of the protein matrix in type II reaction center are correlated to the spin state of non-heme iron. We propose a simple mechanism in which the spin state of non-heme iron directly determines the strength of coupling between the two quinone acceptors (QA and QB) and fast collective motions of protein matrix that play a crucial role in activation and regulation of the electron and proton transfer between these two quinones. We suggest that hydrogen bond network on the acceptor side of reaction center is responsible for stabilization of non-heme iron in different spin states.