bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperfine interactions, magnetic, transport and structural properties of La0.67Ca0.33Mn0.9457Fe0.06O3
Authors: Przewoźnik J. , Żukrowski J. , Chmist J. , Tarnawski Z. , Kołodziejczyk A. , Krop K. , Kellner K. , Gritzner G. 
Published: January 2006

AbstractThe La0.67Ca0.33Mn0.9457Fe0.06O3compound was studied using powder X‐ray diffraction, VSM magnetometry, four‐probe resistance measurements and57Fe Mössbauer spectroscopy. The Mössbauer measurements were performed between 15 K and 850 K and showed good agreement between Curie temperature determined from temperature dependences of the hyperfine field (141 K) and DC magnetization (142 K). They show the inhomogeneous character of the magnetic transition and the coexistence of ferromagnetic and paramagnetic phases in the temperature range 110 K ≤T< 141 K. Our results confirmed that substitution of Fe3+for Mn3+strongly affects the magnetic and transport properties of the parent compound. It causes a difference between Curie temperature and the metal‐insulator transition temperature of about 80 K and a strong reduction of their values. X‐ray diffraction measurements were performed between 4 and 500 K and showed complete suppression of the thermal expansion anomaly at Curie temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic excitations in FCC Mn (37%Fe, 3%Cu) alloy
Authors: Mikke Kazimierz , Jankowska‐Kisielińska Joanna , Hennion Bernard 
Published: January 2006

AbstractWithin the program of our systematic studies of magnetic excitations of manganese alloys the inelastic neutron scattering in FCC Mn(37%Fe,3%Cu) was measured for the temperature range 1.7–600 K. This alloy has the FCC crystal structure both in paramagnetic and AF phase and its composition is close to the range where the enhanced itinerant behaviour was predicted by the theory. The measured spin‐wave velocity and the energy gap in the spin wave spectrum were reported earlier to reach the maximum values in this composition range. Our data did not confirm these earlier results. The expected anisotropy of the inelastic neutron scattering was not found neither in the antiferromagnetic phase nor in the paramagnetic one. The q‐dependence of the spin‐wave damping is quadratic rather than linear and the spin‐wave damping increase with temperature, as usually predicted for damping due to magnon scattering on magnons and on other excitations. This result is in contrast with the data for the FCT Mn(10%Fe,3%Cu) where the q‐dependence of the spin‐wave damping is linear and the damping parameter was found to be temperature independent excepting the region close to TN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of RCoxGe2 (R=Ce, Pr, Gd) compounds
Authors: Penc B. , Szytuła A. , Wawrzyńska E. , Winiarski A. 
Published: January 2006

AbstractThe electronic structure of the RCoxGe2 (R=Ce, Pr, Gd) compounds with the orthorhombic crystal structure of CeNiSi2‐type was studied by X‐ray photoemission spectroscopy. The valence bands of CeCo0.86Ge2 and PrCo0.85Ge2 compounds have the similar character. Near the Fermi level the broad peak corresponding to the Co 3d and R 4f and 5d6s states is observed. In the case of GdCo0.64Ge2, the strong intensity peak at 8.7 eV corresponding to Gd 4f states is observed. The analysis of the XPS spectra of Ce and Pr 3d5/2 and 3d3/2 in the Gunnarson‐Schönhammer model give the information on the hybridization of the f orbital with the conduction band. The hybridization energy equal 93 eV for R=Ce and 143 eV for R=Pr, respectively indicate stability of the shell in these compounds. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase diagrams and multicritical points in the ternary mixed‐spin alloy with a single‐ion anisotropy
Authors: Dely J. , Bobák A. 
Published: January 2006

AbstractThe phase diagram of the ABpC 1–p ternary alloy consisting of different Ising spins SA = 3/2, SB = 2, and SC = 5/2 in the presence of a single‐ion anisotropy is investigated by the use of a mean‐field theory. At finite temperature by changing values of the parameters of the model different types of phase diagrams are obtained, including critical end points and isolated critical points. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The DC and AC insulating properties of magnetic fluids based on transformer oil
Authors: Tomčo L. , Marton K. , Herchl F. , Kopčanský P. , Potočová I. , Koneracká M. , Timko M. 
Published: January 2006

AbstractThe AC‐dielectric breakdown was investigated in magnetic fluids based on transformer oil TECHNOL US 4000 for two orientations of external magnetic field (B ‖ E and B ⊥ E) and in B = 0. The found results were compared with those obtained formerly for the DC‐dielectric breakdown. The observations of the time development of the AC‐dielectric breakdown showed the presence of partial discharges long before the complete breakdown occurrence, while for DC‐dielectric breakdown a complete breakdown of the gap next to the onset of a measurable ionization was characteristic. The comparison of the AC‐dielectric breakdown strengths of pure transformer oil and transformer‐oil‐based magnetic fluid showed better dielectric properties of magnetic fluid in external magnetic field and comparable, but not worse, in B = 0. Regarding to the better heat transfer, provided by magnetic fluids, they could be used in power transformers as insulating fluids. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized theoretical approach to quasi‐one‐dimensional molecular magnets
Authors: Pełka R. , Bałanda M. , Przychodzén P. , Tomala K. , Sieklucka B. , Wasiutyński T. 
Published: January 2006

AbstractTwo quasi‐one‐dimensional compounds [LnIII(terpy)(DMF)4][WV(CN)8] · 6H2O, where Ln stands for Gd or Sm, were synthesized and the measurements of their magnetic features were carried out. Magnetization was measured at 2K in the field range 0–5 T. To extract physical information from the experimental data a generalization of the theoretical approach given by Verdaguer et al. (Phys. Rev. B 29 , 5144 (1984)) [1] is put forward. That theoretical model is found to fit the data well. It allows for the determination not only of the coupling constant but also of the zero‐field splitting parameter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New spin configurations in nano‐sized magnets near reorientation phase transition
Authors: Kisielewski M. , Maziewski A. , Zablotskii V. 
Published: January 2006

AbstractWe review the evolution of magnetization distributions in samples with low magnetic perpendicular‐anisotropy described by the quality factor Q (the relation between anisotropy and demagnetization energies). Infinite ultrathin films, nanowires and disks are studied using real magnetic parameters determined for ultrathin cobalt. By micromagnetic simulations we demonstrate novel types of magnetization distributions. Reconstructions of magnetization distributions at the spin reorientation transition (RPT) from the perpendicular to in‐plane state are discussed. We show that the sample edge significantly affects the magnetization distribution performance and shifts the RPT to lower Q (higher nanostructure thickness) and/or to higher amplitude of in‐plane applied magnetic fields in comparison to those in laterally infinite films. A unified thermodynamic treatment is presented for reorientation transitions in nanowires. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of Ni‐Mn‐Ga Heusler alloy films
Authors: Dubowik J. , Gościańska I. , Kudryavtsev Y. V. , Lee Y. P. , Sovák P. , Konĉ M. 
Published: January 2006

AbstractThe films with composition Nix Mny Gaz (x = 50 ± 5, y = 25 ± 5, z = 25 ± 5) were deposited by flash‐evaporation or sputtering on mica and glass substrates and annealed in a high vacuum at 673–973 K. X‐ray diffraction at room temperature reveals the presence of B2 (or L21) type of structure depending on annealing conditions. Magnetic properties were studied by ferromagnetic resonance at temperatures from 78 K to 400 K and compared with electric resistivity data. It is shown that the magnetic properties of the films critically depend on their structural ordering and microstructure. The films annealed at T < 800 K reveal a complex magnetic behavior due to their specific microstructure while those annealed at T > 800 K show magnetic properties comparable with those of bulk Ni‐Mn‐Ga alloys. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ground‐state properties of the three‐dimensional Falicov‐Kimball model
Authors: Farkašovský Pavol , Čenčariková Hana , Tomašovičová Natália 
Published: January 2006

AbstractThe ground‐state properties of the three‐dimensional spinless Falicov‐Kimball model are studied by a wellcontrolled numerical method. The results obtained are used to categorize the ground‐state configurations according to common features for weak, intermediate and strong interactions. It is shown that only a few configuration types form the basic structure of the phase diagram. In particular, the largest regions of stability correspond to phase segregated configurations, striped configurations and configurations in which electrons are distributed in diagonal planes with incomplete chessboard structure. Near half‐filling, mixtures of two phases with complete and incomplete chessboard structure are determined. In addition, the picture of metal‐insulator transitions is presented. The relevance of these results for a description of real material is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical sound propagation in MnF2
Authors: Pawlak A. 
Published: January 2006

AbstractWe analyse the critical sound attenuation in the antiferromagnet MnF2 above its Neel temperature. A general formula for the acoustic self‐energy, derived in the model in which a sound mode is coupled to both the order‐parameter fluctuations as well as to the energy mode, is applied to interpret the experimental data in MnF2. It has been shown that a very interesting competition between three asymptotic singularities is responsible for the complex behaviour of the sound attenuation coefficient in the high‐temperature phase. The relative strength of these terms depends also on the ultrasonic frequency. For high frequency sound propagation also a background attenuation starts playing an important role. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective sound attenuation exponents in magnets
Authors: Pawlak A. , Fechner B. 
Published: January 2006

AbstractWe try to explain how some magnets belonging to the Heisenberg universality class can be characterised by positive sound attenuation exponents near the critical point. In magnets being also insulators the sound attenuation exponent should be equal to 2α where α is the usual specific‐heat exponent. This exponent is however negative in the Heisenberg universality class. In this paper we interpret the positive attenuation exponents measured in isotropic magnets such as RbMnF3, Y3Fe5O12 and Gd3Fe5O12 in terms of the effective critical exponents. The high value of the sound attenuation exponent in anisotropic FeF2 can also be interpreted in this way. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetization dynamics of perpendicular exchange‐biased (Pt/Co)‐Pt‐IrMn multilayers studied by MOKE microscopy and magnetometry
Authors: Czapkiewicz M. , van Dijken S. , Stobiecki T. , Rak R. , Zoladz M. , Mietniowski P. 
Published: January 2006

AbstractIn this paper the dynamics of the magnetization reversal process in perpendicularly biased [20 Å Pt/5 Å Co]3/t Å Pt/100 Å IrMn/20 Å Pt multilayers with different Pt insertion layer thickness (0 Å ≤ t ≤ 12 Å) is studied. The insertion of 1 Å thick Pt enhances the exchange bias field (Hex ) and for t > 3 Å Hex decreases exponentially with increasing Pt layer thickness. We show by magnetization relaxation measurements and direct observation of magnetic domains that magnetization reversal takes place by the nucleation of isolated cylindrical domains with a different nucleation site density in the forward and backward branches of the hysteresis loop. All the results were quantitatively analyzed using the Fatuzzo model for the dynamics of domain reversal processes. The activation energies for magnetization reversal by domain nucleation and domain propagation were determined. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of roughness on some magnetic properties of layered structures of Fe, Co separated Cu or Au
Authors: Staniucha I. , Urbaniak‐Kucharczyk A. 
Published: January 2006

AbstractThe system of two magnetic (M) layers divided by nonmagnetic (N) spacer is considered. Roughness in interface region is introduced employing model proposed by Bruno and Chappert. Presence of roughness leads to modification of interface exchange parameter and interface anisotropy in comparison to samples with ideal interface. The magnetisation distribution and Curie temperature has been calculated using Green function formalism for systems consisting of Fe or Co standing for M and Cu or Au standing for N, respectively. Parameters corresponding to GaAs have been taken into account to characterize the substrate. The results obtained show decreasing of Curie temperature and shift of magnetisation curve with increasing of roughness parameter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An extended Boltzmann formalism for transport description in thin Fe–Cr–Fe trilayers
Authors: Warda K. , Wojtczak L. , Baldomir D. , Pereiro M. , Arias J. 
Published: January 2006

AbstractWe present the calculations of Giant Magnetoresistance (GMR) for thin trilayers of the type nFe/3Cr/nFe where 1 ≤ n ≤ 8 for the slab geometry. All parameters used for the calculations in Boltzmann approach like the potentials, relaxation times, effective masses and the Fermi energy are determined for the different spin polarisations from electronic structure of trilayer on the base of ab initio method. The value of the parameter P corresponds to the specularity factor in Fuchs–Sondheimer theory. It is responsible for scattering electron from the metallic surface determined in analytical way. The results show a strong dependence of GMR on the ferromagnetic layer thickness as well as on the concentration of scattering centers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diode effect in transport through a quantum dot coupled to non‐collinearly polarized ferromagnetic leads
Authors: Rudziński W. , Świrkowicz R. , Wilczyński M. , Barnaś J. 
Published: January 2006

AbstractElectron tunneling through a spin‐split discrete level of an interacting quantum dot coupled to two ferromagnetic electrodes with non‐collinear magnetizations is investigated theoretically by means of the nonequilibrium Green function approach. It is shown that the spin splitting of the dot level due to an external magnetic field leads to qualitatively new effects. In particular, numerical results show that the negative differential conductance and diode effect may occur in symmetrical junctions with non‐collinear magnetizations and for large enough magnetic polarization of the leads. It is also found that in asymmetrical junctions with one electrode being half‐metallic, the spin splitting gives rise to an enhancement of the diode‐like features in transport characteristics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of Fe layer thickness on electronic and magnetic properties of antiferromagnetically coupled Fe/Si multilayers
Authors: Luciński T. , Wandziuk P. , Baszyński J. , Szymański B. , Stobiecki F. , Zweck J. 
Published: January 2006

AbstractThe antiferromagnetically coupled Fe/Si multilayers deposited by magnetron sputtering with different Fe layer thicknesses have been examined. It has been shown that the magnetization of ferromagnetic layer reduces its value with decreasing Fe layers thickness affecting the antiferromagnetic interlayer coupling. This coupling has been found to occur for Fe layer thicker than 0.5 nm. It has been shown that the antiferromagnetic interlayer coupling occurs through the semiconducting spacer layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic and transport properties of thin GdCo4B alloy films
Authors: Smardz L. , Toliński T. , Luciński T. , Gościańska I. , Szlaferek A. , Trybuła Z. , Kowalczyk A. 
Published: January 2006

AbstractGdCo4B thin films were prepared onto liquid nitrogen (LN) cooled or non‐cooled glass substrates by an UHV flesh evaporation technique. Structural studies showed that the samples deposited onto the LN cooled or non‐cooled glass substrates are amorphous and crystallize after an UHV annealing at 873 K. The resistance of the amorphous thin films increases with temperature decreasing from RT down to 4.2 K, while the annealed samples exhibit metallic behaviour. The crystallization process was observed by resistivity measurements in the temperature range varied from RT to 873 K with a rate of 10 K/min. We have observed a systematic change in the shape and peaks position of the XPS valence band after in‐situ annealing of the “as prepared” amorphous GdCo4B thin films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetization and FMR studies of [Fe/Cr]n structures with ultrathin iron layers
Authors: Drovosekov A. B. , Kreines N. M. , Milyaev M. A. , Romashev L. N. , Ustinov V. V. 
Published: January 2006

AbstractMagnetic multilayer structures [Fe(t Fe)/Cr(t Cr)]n with ultrathin (t Fe < 5 Å) iron layers prepared by a molecular beam epitaxy were studied using SQUID‐magnetometry and ferromagnetic resonance technique. For the samples with t Fe ≳ 3 Å, the obtained magnetization curves and resonance spectra are typical for regular magnetic superlattices. On the contrary, the samples with t Fe ≲ 3 Å demonstrate superparamagnetic‐like behavior. These samples show a strong temperature dependence of their static and resonance magnetic properties. To explain the obtained results, we propose a theoretical model considering a cluster structure of thin iron layers. Magnetization curves and resonance spectra are calculated using an effective field approximation taking into account an interlayer interaction and cluster size distribution. The calculated dependencies show a qualitative agreement with the experimental data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties and 1H NMR spectroscopy of TM22+[WIV(CN)8]·nH2O
Authors: Kováč J. , Zentková M. , Bokor M. , Mihalik M. , Kavečanský V. , Mitróová Z. , Zentko A. , Pekker A. , Kamarás K. 
Published: January 2006

AbstractWe report on magnetic properties of bimetallic extended networks built from [WIV(CN)8]4– and TM2+ = Mn2+ , Fe2+, Co2+, Ni2+, Cu2+ , Zn2+. The weak exchange interaction is the reason for appearance of magnetically ordered state at low temperatures for all compounds with exception of Zn2[W(CN)8].nH2O. It has been shown that susceptibility data for all compounds, except Co2[W(CN)8].5H2O, follows the Curie Weiss law above T = 50 K. For Co2[W(CN)8].5H2O the modified Curie Weiss law is valid. Free induction decay (FID) signals showed behaviour peculiar to paramagnetic samples. The decayed more rapidly in a higher applied static magnetic field B 0 = ω 0/γ 1H. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of Ge substitution in Ni2MnGa1–xGex Heusler alloys and films
Authors: Gościańska I. , Dubowik J. , Kudryavtsev Y. V. , Jezierski A. 
Published: January 2006

AbstractWe present the results on the effect of adding Ge on the magnetic properties of Ni2MnGa1–x Gex (0 < x < 0.4) alloys and thin films deposited by flash‐evaporation from the powdered alloys. It is found that the annealed alloys are single phase with L21 ordering (cubic lattice constant a ≃ 0.581 nm). The Ge addition causes a drastic decrease in the martensitic transformation temperature from T M = 200 K (x = 0) to T M = 50 K (x = 0.4) with almost no effect on the Curie temperature T C ≃ 380 K and magnetization M S (0) ≃ 450–500 G. The magnetic properties of thin films strongly depend on ordering. The ordered films have similar L21 (or B2) ordering and exhibit the magnetic properties similar to the properties of corresponding bulk alloys. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A 55Mn NMR study of the La0.75Sr0.25MnO3 nanoparticles
Authors: Rybicki D. , Sikora M. , Kapusta Cz. , Riedi P.C. , Jirak Z. , Knizek K. , Marysko M. , Pollert E. , Veverka P. 
Published: January 2006

AbstractWe report on a 55Mn NMR study of the La0.75Sr0.25MnO3 nanoparticles of the average grain size 33 nm and 114 nm at 4.2 K and 77 K and at applied field of 0, 0.2 and 0.5T. A dominant signal from the double exchange (DE) controlled metallic ferromagnetic interior of the grains as well as a small signal from insulating ferromagnetic regions is observed. From a comparison with bulk magnetization measurement the thickness of the nonferromagnetic outer layer of the grains and the amount of the ferromagnetic insulating phase was determined. The relative amount of these phases with respect to the ferromagnetic metallic phase increases with decreasing grain size. The DE line in the NMR spectrum shows a frequency shift with applied field according to a full 55Mn gyromagnetic ratio. A value of the demagnetizing field close to zero is obtained, which indicates a single domain state of the nanoparticles. For the sample with larger grains a higher NMR enhancement is observed, which indicates a higher magnetic susceptibility of the sample at the NMR frequencies. A comparison with the NMR data obtained on a microcrystalline material is made. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal expansion of RIn3 compounds with R=Pr,Gd and Lu
Authors: Sołyga M. , Czopnik A. , Pluznikov V. , Ulner J. , Durczewski K. , Kletowski Z. 
Published: January 2006

AbstractResults of the linear thermal expansion coefficient α (T ) measurements for PrIn3, GdIn3 and LuIn3 are reported. These rare earth intermetallic compounds belong to a large family of RIn3 compounds which crystallize in AuCu3‐type crystal structure. The measurements were made on monocrystalline samples in temperature range 5K ÷ 200 K. The compounds under investigation differ in their magnetic properties: PrIn3 is a typical example of a singlet ground‐state paramagnet in which the interionic interactions are quenched by the crystalline electric field (CEF), whereas GdIn3 is the crystal‐field free antiferromagnet in which the interionic RKKY interactions play essential role and cause the antiferromagnetic structure which is still unknown. The results of the measurements for LuIn3 served as a non‐magnetic background for the separation of the contribution to α (T ) arising from the magnetic interaction. Theoretical considerations concerning the influence of CEF on the thermal expansion are remined. Pertinent Grüneisen parameters will be estimated in a forthcoming paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical properties of carbon doped EuB6
Authors: Bat'ková M. , Bat'ko I. , Mihalik M. , Konovalova E. S. , Shitsevalova N. , Paderno Y. 
Published: January 2006

AbstractWe report results of electrical resistivity and tunnelling spectroscopy studies of carbon doped EuB6 showing a colossal magnetoresistance effect. Performed tunnelling spectroscopy studies confirm a metallic‐like nature of the system. The electrical resistivity studies reveal, it is a spin‐disorder scattering that dominates in the temperature region 10.3–20 K and the magnetic phase transition temperature is T c = 4.1 K. Due to similarities of the temperature dependence of the resistivity with ones reported for stoichiometric and lanthanum substituted EuB6, the resistivity behavior in the intermediate temperature region is expected to be strongly influenced by the formation of magnetic polarons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)