Pinning Fields In Amorphous Materials

The stress and field dependence of the pinning field Hp of ribbons of the composition Fe73.5Cu1Nb3Si 13.5B9 and Co73.5Cu1Nb 3Si13.5B9 is compared with that of the coercivity HC. The similar character of HC(σ) and Hp(σ) indicates a strong correlation between these two properties. At higher external stresses HC(σ) and H p(σ) depend on a premagnetizing procedure. This can be explained assuming a different domain structure.731057275729New University of Lisbon,UNINOVA,Universiteit van Amsterda

The Influence Of Quenching Rate On Magnetic Properties Of Amorphous Ribbons

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Five sets of amorphous ribbons of the composition Fe73.5Cu 1Nb3Si13.5B9 produced with different quenching rates (QR) were studied in order to verify the influence of the topological disorder on magnetic properties. For this purpose several magnetic methods were applied. Significant differences have been found between the results of magnetic disaccommodation He·Δμ/μ, pinning field Hp and stress dependence of the magnetic permeability μ/μ0(σ) of as-cast materials produced at different QR. The values of He·Δμ/μ and Hp are directly proportional to the disorder degree of the samples. The μ/μ0(σ) curves display broad maxima, which are found to be related to the quenched-in stresses. In contrast with these results, no significant effects of the amorphous structure on the Curie temperature and Mössbauer spectra were found, because other parameters are dominating.7310660366052011/01071-3; FAPESP; São Paulo Research FoundationFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Frequency Dependence Of The Magnetoimpedance In Amorphous Cop Electrodeposited Layers

Magnetic properties and changes of impedance upon external field (MI) are studied in amorphous CoP magnetic layers obtained by galvanostatic electrodeposition over cylindrical Cu substrates. The magnetic layer thickness is controlled by deposition time and varies between 3 and 7 μm. Due to the columnar growth of Co, thicker layers have stronger perpendicular radial anisotropy. The field and frequency dependence of the impedance is measured in the kHz/MHz range. Although it is generally accepted that a radial anisotropy should be unfavorable to the MI effect, an increase of the MI ratio with the thickness of the magnetic layer, and thus with anisotropy, is observed. Results are explained in terms of a model considering the current distribution along the sample thickness with two well-defined regions having different transport and magnetic properties. © 2000 American Institute of Physics.879 II48254827Landau, L.D., Lifshitz, E.M., (1975) Electrodynamics of Continuous Media, p. 195. , Pergamon, OxfordPanina, L.V., Mohri, K., Uchiyama, T., Noda, M., (1995) IEEE Trans. Magn., 31, p. 1249Beach, R.S., Berkowitz, A.E., (1994) Appl. Phys. Lett., 64, p. 3652Rao, K.V., Humphrey, F.B., Costa-Kramër, J.L., (1994) J. Appl. Phys., 76, p. 6204Knobel, M., Sánchez, M.L., Velázquez, J., Vázquez, M., (1995) J. Phys.: Condens. Matter, 7, pp. L-115Sommer, R.L., Chien, C.L., (1995) Appl. Phys. Lett., 67, p. 3346Panina, L.V., Mohri, K., (1996) J. Magn. Magn. Mater., 157-158, p. 137Vázquez, M., Zhukov, A.P., Aragoneses, P., Arcas, J., García-Beneytez, J.M., Marin, P., Hernando, A., IEEE Trans. Magn., , in pressBeach, R.S., Smith, N., Platt, C.L., Jeffers, F., Berkowitz, A.E., (1996) Appl. Phys. Lett., 68, p. 2753Usov, N., Antonov, A., Granovsky, A., (1997) J. Magn. Magn. Mater., 171, p. 64Favieres, C., Aroca, C., Sánchez, M.C., Rao, K.V., Madurga, V., (1998) J. Magn. Magn. Mater., 177-181, p. 107Vázquez, M., Sinnecker, J.P., Kurlyandskaya, G.V., (1999) Mater. Sci. Forum, 302-303, p. 209Sinnecker, J.P., Knobel, M., Sartorelli, M.L., Schonmaker, J., Silva, F.C.S., (1998) J. Phys. IV, 8 (PR2), p. 665Machado, F.L.A., Rodrigues, A.R., Puça, A.A., De Araujo, A.E.P., (1999) Mat. Sci. Forum, 302-303, p. 202Cargil III, G.S., Gambino, R.J., Cuomo, J.J., (1974) IEEE Trans. Magn., MAG-10, p. 803Dietz, G., Bestgen, H., Hungenberg, J., (1978) J. Magn. Magn. Mater., 9, p. 208Riveiro, J.M., Sánchez-Trujillo, M.C., (1980) IEEE Trans. Magn., MAG-16, p. 1426Luborsky, F.E., (1983) Amorphous Metallic Alloys, , Butterworths, LondonMénard, D., Britel, M., Ciureanu, P., Yelon, A., (1998) J. Appl. Phys., 84, p. 2805Kraus, L., (1999) J. Magn. Magn. Mater., 195, p. 764Yelon, A., Ménard, D., Britel, M., Ciureanu, P., (1996) Appl. Phys. Lett., 69, p. 308

Coercivity behavior in Gd(Co1−xCux)5 system as function of the microstructureevolution

AbstractMagnetic measurements, X-ray diffraction and scanning electron microscopy (SEM) experiments were carried out in the as-cast Gd(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

Morphology and magnetism of multifunctional nanostructured γ\gamma-Fe2_2O3_3 films: Simulation and experiments

This paper introduces a new approach for simulating magnetic properties of nanocomposites comprising magnetic particles embedded in a non-magnetic matrix, taking into account the 3D structure of the system in which particles' positions correctly mimic real samples. The proposed approach develops a multistage simulation procedure in which the size and distribution of particles within the hosting matrix is firstly attained by means of the Cell Dynamic System (CDS) model. The 3D structure provided by the CDS step is further employed in a Monte Carlo (MC) simulation of zero-field-cooled/field-cooled (ZFC/FC) and magnetic hysteresis loops ($M \times H$ curves) for the system. Simulations are aimed to draw a realistic picture of the as-produced ultra-thin films comprising maghemite nanoparticles dispersed in polyaniline. Comparison (ZFC/FC and $M \times H$ curves) between experiments and simulations regarding the maximum of the ZFC curve ($T_{\scriptsize MAX}$), remanence ($M_R/M_s$) and coercivity ($H_C$) revealed the great accuracy of the multistage approach proposed here while providing information about the system's morphology and magnetic properties. For a typical sample the value we found experimentally for $T_{\scriptsize MAX}$ (54 K) was very close to the value provided by the simulation (53 K). For the parameters depending on the nanoparticle clustering the experimental values were consistently lower ($M_R/M_s$ = 0.32 and $H_C$ = 210 Oe) than the values we found in the simulation ($M_R/M_s$ = 0.53 and $H_C$ = 274 Oe). Indeed, the approach introduced here is very promising for the design of real magnetic nanocomposite samples with optimized features.Comment: 19 pages (one column), 5 figure

Magneto-impedance Relaxation In Amorphous Wires And Ribbons

Measurements of the impedance decay after the removal of a saturating magnetic field (H = 7.9 kA/m) for amorphous wire and ribbons are presented, for different frequencies and amplitudes of the driving field. © 1998 Elsevier Science B.V. All rights reserved.177-181PART 1121122Sinnecker, J.P., Sartorelli, M.L., Schoenmaker, J., Knobel, M., Silva, F.C.S., J. de Phys., , in pressKnobel, M., Sartorelli, M.L., Sinnecker, J.P., (1997) Phys. Rev. B, 55, pp. R3362Sartorelli, M.L., Knobel, M., Schoenmaker, J., Gutierrez, J., Barandiarán, J.M., (1997) Appl. Phys. Lett., 71, p. 2208Allia, P., Beatrice, C., Mazzetti, P., Vinai, F., (1987) Appl. Phys. Lett., 51, p. 142Allia, P., Vinai, F., (1990) Philas. Mag. B, 61, p. 76

Giant magneto-impedance in glass covered microwires

Giant magneto-impedance ratio in glass covered Co68.5Mn6.5Si10B15 microwires, with different glass coat thickness, was measured as a function of de axial field (up to 10.5 kA/m) and frequency (f=0.5 MHz up to 30 MHz). A maximum GMI ratio of 58% was observed at 1.5 MHz. The frequency dependence of the GMI maximum and the position where it occurs is discussed in terms of the glass coat thickness

Coercivity And Disaccommodation On Amorphous (fe1-xrx)80b20

Amorphous ribbons of the composition (Fe1-xRx)80B20 (R = Y, Ce, Pr, Nd, Sm, Gd, Ho, Er, Tm, Lu) (0{precedes above single-line equals sign}x{precedes above single-line equals sign}0.08) were studied by means of disaccommodation measurements, pinning field and coercivity measurements. The after-effect scales roughly with the square of the magnetostriction constant. The concentration dependence of the pinning field can be correlated with that of the coercivity. © 1994.1331-3270272Idzikowski, Wrzeciono, (1988) Phys. Stat. Solidi (a), 108, p. 375Khan, (1990) J. Magn. Magn. Mater., 86, p. L143Tejada, Martinez, Labarta, Grössinger, Hernando, (1990) J. Appl. Phys., 67, p. 5984Polak, (1992) Thesis, , University of ViennaJ.P. Sinnecker, M. Knobel, J.F. Saenger and R. Sato Turtelli, Proc. EMMA'93 (Kosice)Narita, Yamasaki, Fukunaga, (1980) IEEE Trans. Magn., 16, p. 435Grössinger, Wezulek, Sassik, The influence of the magnetostriction on the coercivity of amorphous ribbons (1990) Journal of Magnetism and Magnetic Materials, 83, p. 351Sinnecker, Grössinger, Turtelli, Exel, Greifeneder, Kuβ, (1994) J. Magn. Magn. Mater., 133, p. 20. , (this volume)Rezende, Turtelli, Missel, (1987) IEEE Trans. Magn., 23, p. 212

Initial Magnetic Permeability During The Development Of The Nanocrystalline State In Amorphous Ribbons

Low-field initial permeability (μi) has been measured at several steps of nanocrystallization in four amorphous Fe73.5Cu1Nb3Si13.5B9 ribbons produced by planar flow casting with different quenching rates (QRs) from the melt. It is observed that the increase in μi upon nanocrystallization is strongly influenced by the initial free-volume content of each sample. Samples produced with higher quenching rates exhibit a faster transformation kinetics and stronger enhancement of the initial permeability in the nanocrystalline state. Conventional heat treatments and accumulative annealings were performed on all the ribbons, in order to study the effect of their inhomogeneities and induced anisotropies. © 1994.1331-3255258Yoshizawa, Oguma, Yamauchi, (1988) J. Appl. Phys., 64, p. 6044Knobel, Turtelli, Rechenberg, (1992) J. Appl. Phys., 71, p. 6008Köster, Herold, Glassy Metals I: Ionic Structure (1981) Electronic Transport and Crystallization, p. 254. , H.J. Güntherodt, H. Becker, Springer-Verlag, BerlinKnobel, Sinnecker, Saenger, Turtelli, Effect of as-cast topological disorder on the magnetic properties of nanocrystalline Fe73.5Cu1Nb3Si13.5.B9 (1993) Philosophical Magazine Part B, 68, p. 861C. Polak, M. Knobel, R. Grössinger and R. Sato Turtelli, J. Magn. Magn. Mater. (to appear)P. Allia, M. Baricco, M. Knobel, P. Tiberto and F. Vinai, IEEE Trans. Magn. (in press)Knobel, Sinnecker, Turtelli, Rechenberg, Grössinger, (1993) J. Appl. Phys., 73, p. 6603Knobel, Santos, Torriani, Turtelli, (1993) Nanostr. Mater., 2, p. 399Luborsky, (1983) Amorphous Metallic Alloys, p. 360. , F.E. Luborsky, Butterworths, Londo