R. Grössinger

Vienna University of Technology, Wien, Vienna, Austria

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Publications (295)447.16 Total impact

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    ABSTRACT: The present work analyzes the influence of electric conductivity on the Magnetic Barkhausen Noise (MBN) signal using a microscopic model which includes the influence of eddy currents. This model is also implemented to explain the dependence of MBN on the frequency of the applied magnetic field. The results presented in this work allow analyzing the influence of eddy currents on MBN signals for different values of the material's electric conductivity and for different frequencies of applied magnetic field. Additionally, the outcomes of this research can be used as a reference to differentiate the influence of eddy currents from that of second phase particles in the MBN signal, which has been reported in previous works.
    No preview · Article · Mar 2016 · Journal of Magnetism and Magnetic Materials
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    ABSTRACT: This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements.
    Full-text · Article · Mar 2016 · Journal of Magnetism and Magnetic Materials
  • R Grössinger · N Mehboob · M Zehetbauer
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    ABSTRACT: The effect of SPD treatment on the hysteresis properties of selected soft magnetic materials such as Fe3%Si and Fe17%Co steel is presented. The enhancement of the coercivity due to the mechanical deformation can be explained by the magnetoelastic energy Ehe frequency dependence of the coercivity and of the losses can be described using an eddy current based model.
    No preview · Article · Jun 2014 · IOP Conference Series Materials Science and Engineering
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    ABSTRACT: Investigation of the magnetostriction in Fe100-xMnx alloys with x = 45, 48, 50, 52 and 55, in as-cast, annealed and cold-rolled states was performed. The magnetostriction was measured by two methods: capacitance dilatometer and strain-gauge bridge. A careful structure characterization was made by XRD. For all samples the magnetostriction measured at room temperature was quasi-zero. Additionally, we found an orthorhombic structure for as-cast and annealed samples. These results are in strong disagreement with those reported in literature. Possible reasons for these disagreements are briefly discussed.
    Full-text · Article · Jun 2014 · IOP Conference Series Materials Science and Engineering
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    R Grössinger · R Sato Turtelli · N Mehmood
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    ABSTRACT: The magnetostrictive properties of cubic Laves phases such as TbFe2, Terfenol D and SmFe2 are summarised. It is shown that SmFe2 can be an interesting candidate as a high magnetostrictive material even in the as cast "dirty" state. Fe-X alloys based on Fe-Ga but also Fe-Al are presented as materials with a medium magnetostriction, however with the big advantage of a magnetically soft material. Generally all nonmagnetic substutional elements which cause an increase of the interatomic distance in the Fe-lattice (such as Ga, Al, Si) cause an increase of the magnetostriction too. In Ni-Ga a reduction of the magnetostriction was found. Another interesting material with high magnetostriction is CoFe2O4 which is cheap, easy to produce and an oxidic material. Here magnetostriction values up to 400 ppm can be achieved by hydrostatic compaction followed by a field annealing.
    Full-text · Article · Jun 2014 · IOP Conference Series Materials Science and Engineering
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    R Sato Turtelli · M Kriegisch · M Atif · R Grössinger
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    ABSTRACT: The development of Co-ferrite nanocrystals, and bulk materials for magnetostrictive applications is reviewed. This includes magnetic and structural properties and also processing conditions which are of special importance to increase the magnetostriction as well as to achieve very fine Co-ferrite nanocrystals. The magnetic properties of a single crystal, where a field induced phase transition was found, are also presented.
    Full-text · Article · Jun 2014 · IOP Conference Series Materials Science and Engineering
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    ABSTRACT: The effect of Mn substitution on temperature dependent magnetic properties of Mn substituted cobalt ferrite, i.e., Co1−xMnxFe2O4 (x=0.0–0.4), prepared by a ceramic method has been investigated. X-ray diffraction (XRD) analysis reveals that all samples posses a single phase cubic spinel structure. The lattice constant determined from XRD increases with Mn substitution whereas the bulk density of the samples decreases. Mössbauer results reveal that Co, Fe and Mn ions are distributed over the tetrahedral (A) and octahedral (B) sites for the prepared samples. Hysteresis loops yield a saturation magnetization (Ms) and coercive field (Hc) that vary significantly with temperature and Mn content (x). The temperature dependence of the magnetization obtained for μoH=5 T presents a maximum at 175 K which is also dependent on the value of x. The high field regimes of the hysteresis loops are modeled using the Law of Approach to Saturation (LAS) to determine the first-order cubic anisotropy coefficient (K1). It has been found that the anisotropy of these materials increases significantly with decreasing temperature. However, below 175 K, the shape of the anisotropy energy function changes significantly causing a first-order magnetization process (FOMP) at higher fields, which also prevents the magnetization to saturate even under a maximum applied field of 5 T. In general, the anisotropy coefficient decreases with increasing Mn substitution at a given temperature, which could be explained in terms of the site occupancy of the Mn2+ substituent in the cubic spinel lattice.
    Full-text · Article · Jan 2014 · Ceramics International
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    Mukhtar Ahmad · Ihsan Ali · R. Grössinger · M.U. Rana
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    ABSTRACT: The effects of Al-substitution on electrical, magnetic and high frequency dielectric parameters of single phase BaCo2AlxFe16-xO27 (x = 0-1) hexaferrites have been discussed in the present work. The XRD patterns reveal the single phase formation of these ferrites. Bulk density, X-ray density and porosity as a function of Al contents were calculated. Incorporation of Al into the W-type hexagonal structure was confirmed by energy-dispersive X-ray spectroscopic (EDXS) technique. The DC resistivity was observed to increase with increasing Al contents due to the unavailability of Fe3+ ions. The M-H loops were measured up to a maximum applied field of 9 T. The saturation magnetization (M-s) values were calculated by the law of approach to saturation. The coercivity (H-c) values for all the samples lie in the range of a few hundred oersteds which is one of the necessary conditions for EM materials, security, switching and sensing applications. The high frequency dielectric constant and dielectric loss in the frequency range of 0.025-1.5 GHz were observed to decrease as a function of Al contents which are favorable for high frequency applications and microwave devices like dielectric resonators.
    Full-text · Article · May 2013 · Journal of Alloys and Compounds
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    Mukhtar Ahmad · Ihsan Ali · R. Grössinger · M. Kriegisch · F. Kubel · M.U. Rana
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    ABSTRACT: Abstract Divalent (Me) ions substituted W-type hexagonal ferrites with chemical formula Ba0.5Sr0.5Co2-xMexFe16O27 (x=0, 0.5 and Me=Mn, Mg, Zn, Ni) were prepared by sol-gel autocombustion method at 1300°C for 5 h. Thermal and IR spectral studies were carried out by means of differential thermal/thermogravimetric analysis and Fourier transform infrared spectroscopy respectively. The microstructure was investigated by using the powder X-ray diffractometer and the field emission gun scanning electron microscope. The results showed that divalent ions substituted W-type hexagonal ferrites were single phase and appeared as hexagonal platelet-like shape which is better shape for microwave absorption. M-H loops of a selected sample were measured up to maximum applied field of 9T in a temperature range of 4.2K-400K. The values of saturation magnetization were calculated by the law of approach to saturation. The room temperature value of coercivity is found to be a few oersteds which is favorable for EM materials. Based on the results of electromagnetic parameters, reflection losses were calculated which are found to depend on the thickness of the absorber.
    Full-text · Article · May 2013 · Journal of Alloys and Compounds
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    Mukhtar Ahmad · R. Groessinger · M. Kriegisch · F. Kubel · M. U. Rana
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    ABSTRACT: The magnetic and microwave characterization of single phase hexaferrites of entirely new composition Ba1-xSrxCo2AlFe15O27 (x=0.2–1.0) for application in a microwave absorber, have been reported. The samples synthesized by sol–gel method were investigated by differential thermal analyzer, Fourier transform infrared spectroscope, X-ray diffractometer, field emission gun scanning electron microscope, vibrating sample magnetometer and vector network analyzer. Platelet grains exhibit well defined hexagonal shape which is a better shape for microwave absorption. M–H loops for a selected sample were measured for a temperature range of 4.2–400 K. Moreover M–H loops for all Sr-substituted samples were also measured at room temperature up to a maximum applied field of 9 T. Saturation magnetization values were calculated by the law of approach to saturation. The room temperature coercivity for all the samples is found to be a few hundred oersteds which is necessary for electromagnetic materials and makes these ferrites ideal for microwave devices, security, switching and sensing applications. The complex permittivity, permeability and reflection losses of a selected ferrite–epoxy composite were also investigated over a frequency range of 0.5–13 GHz.
    Full-text · Article · Apr 2013
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    ABSTRACT: Magnetic measurements, X-ray diffraction and scanning electron microscopy (SEM) experiments were carried out in the as-cast Gd(Co1−xCux)5Gd(Co1−xCux)5 samples with different Co/Cu content. Already in the as cast state, this system shows high coercive field for x=0.3 and a magnetization driven by nucleation of reversal domain. SEM micrograph and microanalysis show possible spinodal decomposition in the as-cast state, hence regions with different Co/Cu-content are observed, while the Gd-content almost does not change. High resolution X-ray diffraction patterns show a main CaCu5-type structure with traces of a secondary phase and distorted peak profiles as function of the Cu content. The evolution of the microstructure is discussed in relation with the Cu incorporation into the CaCu5-type structure. The Cu addition avoids the formation of the 2:7 phase within the 1:5 matrix, favoring the formation of a more homogeneous Gd(Co,Cu)5 phase. The relation between the observed microstructure and the magnetic behavior is also discussed.
    Full-text · Article · Jan 2013 · Physica B Condensed Matter
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    Mukhtar Ahmad · R. Groessinger · M. Kriegisch · F. Kubel · M.U. Rana
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    ABSTRACT: A series of Al-substituted Co2W hexaferrites BaCo2AlxFe16 − xO27 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) synthesized by sol-gel autocombustion method have been investigated. The samples were characterized by DTA/TGA analysis, FTIR spectroscopy, X-ray Diffractometer and field emission gun scanning electron microscopy (FEGSEM). Magnetic behavior of a selected sample was examined up to a magnetic field of 9T between a temperature range of 4.2 K–400 K. The values of saturation magnetization were calculated by the law of approach to saturation. The coercivity of the investigated sample has a value of about hundred oersteds at room temperature which is favorable for EM materials. The complex permittivity and complex permeability of a composite sample have been measured in the frequency range of 0.5–13 GHz. Based on the theoretical calculation of reflection loss; the microwave absorption properties have been investigated. The results indicate that the attenuation peak frequency of these compounds can be tuned for the desired frequency by varying the thickness of the absorber.
    Full-text · Article · Nov 2012
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    ABSTRACT: The modified oxalate precursor method was used for the preparation of nanocrystalline CoFe 2O 4. Structural investigations of as-produced powders performed by means of high-resolution transmission electron microscopy and X-ray diffraction revealed an average particle size of 8 nm. The nanocrystallites are pure CoFe 2O 4 and present a well crystallized spinel structure with lattice constant of 8.3583 Å. The particles are superparamagnetic exhibiting a blocking temperature around room temperature. The magnetization and the coercive field values obtained at 9 T are 56.8 emu · g -1 and 17.0 kOe (at 4.2 K), respectively. The crystalline anisotropy determined from the coercive field as a function of temperature is 8.0 × 10 5 J · m -3, which is much higher than that of bulk materials.
    Full-text · Article · Sep 2012 · International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde)
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    ABSTRACT: Heusler alloy Ni50.0Mn35.5In14.5 ribbons were prepared by melt-spinning technique. Several short time annealings were carried out in order to enhance the exchange bias effect in this alloy ribbon. The magnetic transition temperature increases with the annealing, compared to the as-spun sample, however no significant differences in respective Curie temperatures were observed for austenite and martensite phases in such annealed samples. Exchange bias effect is observed at low temperatures for all samples and practically vanishes at 60 K for the as-spun sample, whereas for the annealed ribbons it vanishes at 100 K.
    Full-text · Article · Feb 2012 · Journal of Magnetism and Magnetic Materials
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    ABSTRACT: Microscopic, element selective structural and magnetic properties of cobalt ferrite produced by sol–gel (SG) and by ball milling (BM) methods were studied with X-ray absorption near-edge structure (XANES) spectroscopy and X-ray emission spectroscopy (XES). All investigated samples exhibit only Fe3+ and Co2+ cations. The relative distribution of the Co2+ and Fe3+ cations in the tetrahedral and octahedral sites depends on the production method of the samples. For the samples presenting a similar but small grain size (<400 nm), the quantity of Co2+ in B-sites of SG sample is less than that in BM sample. These results are in agreement with magnetic measurements, which BM samples exhibit smaller saturation magnetization as compared with those obtained for SG samples. Additionally the coercive field and magnetostriction are larger in BM samples. All these magnetic properties are dependent on annealing parameters (temperature and time). However for samples with large grain sizes their magnetic properties become insensitive to production processes.
    Full-text · Article · Feb 2012 · Materials Chemistry and Physics
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    ABSTRACT: It turns out from our investigations on YCo4+δ B1−δ (δ=0, ±0.1, ±0.2) that the CeCo4B structure is stable for a considerable range of δ. Upon increasing the B content, the saturation magnetisation decreases, the spin reorientation temperature is nearly unchanged but the character of the spin reorientation process is strongly affected.
    No preview · Article · Jan 2012 · International Journal of Modern Physics B
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    ABSTRACT: We have proposed to build a 100 T/10 ms, 70 T/100 ms, 60 T/1 s pulsed field user facility with a 50 MJ capacitor bank at the Forschungszentrum Rossendorf near Dresden. This would provide the appealing possibility to have access to Zeeman energies in the energy range of the infrared free-electron-lasers (5 μm to 150 μm; 2 ps; cw; > 10 W) now under construction at the radiation source ELBE (superconducting electron linear accelerator; 40 MeV; 1 mA; 2 ps; cw) in Rossendorf. The work is accompanied by computer simulations of the planned coil systems, of the power supply, and by the development of high-strength conductors aiming at a tensile strength of about 1.5 GPa at σ ≈ σ Cu/2 (microcomposite CuAg alloys and Cu-steel macro compounds). With a view of gaining experience in the construction and operation of pulsed magnets, a pilot pulsed field laboratory was established at the Institute of Solid State and Materials Research Dresden (IFW Dresden). The laboratory includes short pulse magnets with peak field up to 60 T in a 24 mm bore and a rise time of about 10 ms (coil from NHMFL, Tallahassee), and a 40 T long pulse magnet with 24 mm bore and rise time of about 80 ms (coil from METIS, Leuven). The repetition rate of 20 min between pulses is limited by the cooling time of the coils. The coils are energized by a 1 MJ, 10 kV capacitor bank with some special features. With this set-up measurements of magnetization and magnetotransport on 4f-electron systems, for example RECu2, have been out in the temperature range of 1.5 to 300 K and at fields up to 52 T using high precision pick-up coils.
    Full-text · Article · Jan 2012 · International Journal of Modern Physics B
  • R. Grössinger · S. Sorta · R. Sato Turtelli
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    ABSTRACT: Different experimental possibilities to measure the magnetostriction are discussed. Special emphasis is laid on the measurement of the magnetostriction of ribbon shaped samples. For this purpose crystalline Fe85Ga15 ribbons, an amorphous Fe66Co18Si1B15 sample and a crystalline Fe83.5Si16.5 ribbon were investigated at room temperature. In this work, measurements of magnetostriction using SAMR and standard strain gauge methods were performed and the results were compared. In order to investigate the influence of stress on magnetostriction of Fe85Ga15, the hysteresis loop was measured applying different stresses. The stress dependence of the coercivity shows a minimum at around 120MPa, which value corresponds to the onset of deviation from the initial coefficient dHdc/dσ in SAMR method.
    No preview · Article · Jan 2012
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    ABSTRACT: In this work, the structural and magnetic properties of Tb3 (Fe28−xCox) V1.0 (x=0, 3, 6) compounds have been investigated. The structural characterization of compounds by X-ray powder diffraction is an evidence for a monoclinic Nd3(Fe, Ti)29-type structure (A2/m space group). The refined lattice parameters a and b (but not c) and the unit cell volume V, obtained from the XRD data by the Rietveld method, are found to decrease with increasing Co concentration. The unit cell parameters behavior has been attributed to the smaller Co atoms and a preferential substitution of Fe by Co. The anisotropy field (Ha) as well as critical field (Hcr) was measured using the singular point detection (SPD) technique from 5 to 300 K in a pulsed magnetic field of up to 30 T. At T=5 K, a FOMP of type 2 was observed for all samples and persists at all temperatures up to 300 K. For sample x=0, Hcr=10.6 and 2.0 T at 5 and 300 K, respectively, is equal to that reported earlier. The occurrence of canting angles between the magnetic sublattices during the magnetization process instead of high-order anisotropy contributions (at room temperature are usually negligible) has been considered to explain the survival of the FOMP at room temperature. The anisotropy and critical fields behave differently for samples with x=0, 3 compared with x=6. The observed behavior has been related to the fact that the Co substitution for Fe takes place with a preferential entrance in the inequivalent crystallographic sites of the 3:29 structure. The contribution of the Tb-sublattice in the Tb3(Fe, V)29 compound with uniaxial anisotropy has been scaled from the anisotropy field measured on a Y3(Fe, V)29 single crystal with easy plane anisotropy.
    Full-text · Article · Sep 2011 · Physica B Condensed Matter
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    ABSTRACT: We investigate the influence of Cu substitution, on the coercivity and magnetic viscosity, in the ternary system GdCo5−xCux (x=0, 0.5, 1, 1.5, 2 and 2.5) with different field sweep rates. All samples have been studied in the as cast state and crystallize in a single phase CaCu5 structure. With Cu addition, the coercivity was 10 times enhanced for x =1.5. The behavior of the coercivity Hc against field sweep rate, dH/dt, shows that the GdCo5−xCux system exhibits only a small magnetic viscosity effect, a desirable property for magnetic dynamic applications under high magnetic field.Highlights► The main objective of this work is to understand the role of Cu addition in the coercivity and magnetic viscosity of the GdCo5 system. ► The magnetic measurements were carried out with different techniques and field sweep rates. ► All samples have been studied in the as cast state. With Cu addition, the coercivity was 10 times enhanced for x=1.5. ► The behavior of the coercivity HC against field sweep rate, dH/dt, shows that the GdCo5−xCux system exhibits only a small magnetic viscosity effect, a desirable property for magnetic dynamic applications under high magnetic field.
    No preview · Article · Jul 2011 · Journal of Magnetism and Magnetic Materials

Publication Stats

3k Citations
447.16 Total Impact Points

Institutions

  • 1980-2016
    • Vienna University of Technology
      • • Institute of Solid State Physics
      • • Institute of Sensor and Actuator Systems
      • • Institute of Applied Physics
      Wien, Vienna, Austria
  • 2014
    • Air University of Islamabad
      • Department of Physics
      Islāmābād, Islāmābād, Pakistan
    • IST Austria
      Klosterneuberg, Lower Austria, Austria
  • 1979-2011
    • University of Vienna
      • Fakultät für Physik
      Wien, Vienna, Austria
  • 2009
    • Federal University of Rio de Janeiro
      • Instituto de Física (IF)
      Rio de Janeiro, Rio de Janeiro, Brazil
  • 2005
    • VACUUMSCHMELZE GmbH & Co. KG
      Hanau, Hesse, Germany
  • 2003
    • Chinese Academy of Sciences
      Peping, Beijing, China
  • 1995
    • University of Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 1975
    • Pädagogische Hochschule Wien
      Wien, Vienna, Austria