Stress dependence and effect of plastic deformation on magnetic hysteresis and anhysteretic magnetization of FeNi32% films

Journal of Applied Physics, 101(9): pp. 09-508.The magnetic hysteresis and anhysteretic magnetization of FeNi32% films were investigated as a function of isotropic stress. The magnetostriction contribution to dc magnetization under elastic stress and the effect of the plastic strain on the hysteresis loops are discussed. Also, a role of the plastic deformation interrelated with the elastic stress in the magnetization process is established. An experimental system based on a conventional vibrating sample magnetometer equipped with a specially designed loading fixture and optical resonant spectroscopy tension monitoring technique are used to measure anhysteretic permeability and magnetization curve as a function of stress. Measurements of magnetostriction as a function of magnetic field were shown to be also possible using this fixture. Stresses are deduced from the characteristic resonant frequency of the sample in the fixture and verified via pulse propagation velocity measurement. Both indirect stress measurements are contactless, relying on remote vibration measurement using a laser Doppler vibrometer. Uniaxial stresses up to 1 GPa can be applied for samples down to 50 m specimens. Anhysteretic permeability was extracted from the anhysteretic B-H curves constructed by degaussing the sample at the given longitudinal parallel to the stresses dc field. The large positive magnetostriction constant leads to higher susceptibility and lower coercivity with tensile stress while the large volume magnetostriction results in reduced saturation magnetization. Large stresses imposed on the sample result in plastic strain of the sample which induces increase in dislocation density and domain wall pinning. This causes the gain in hysteresis loss and coercivity to increase at the highest stresses

Microwave magnetoabsorption in glass-coated amorphous microwires with radii close to skin depth

[EN] We present the frequency dependence of microwave magnetoabsorption in glass-coated amorphous microwires of (Co100-xFex)(72.5)Si12.5B15. The data were taken at room temperature in the frequency range of 1-60 GHz for fields up to 15 kOe by either a cavity perturbation technique or a coaxial transmission line. The resulting spectra strongly depend upon the local microwave magnetic and electric fields. We have found that we can simulate the spectra using an analytic solution to the problem of electromagnetic scattering from a cylinder. We demonstrate that these unusual spectra can be interpreted in terms of ferromagnetic resonance and antiferromagnetic resonance. However, because the electromagnetic skin depth is comparable to the radius, the resonance and antiresonance fields do not follow the conventional equations. (C) 2002 American Institute of Physics.Lofland, S.; García Miquel, ÁH.; Vázquez, M.; Bhagat, S. (2002). Microwave magnetoabsorption in glass-coated amorphous microwires with radii close to skin depth. Journal of Applied Physics. 92(4):2058-2063. doi:10.1063/1.1494847S2058206392

Ferromagnetic resonance in FeCoNi electroplated wires

[EN] We have investigated the microwave properties (ferromagnetic resonance and ferromagnetic antiresonance) of FeCoNi magnetic tubes created by electroplating on CuBe wire. Important parameters such as the g factor, magnetization, anisotropy field, and damping parameter were obtained from the measurements. One sample, prepared by a method which entails rf-sputtering deposition of an additional FeNi layer, shows a clear ferromagnetic antiresonance. (C) 2003 American Institute of Physics.This work was partially supported by Spanish Secretaria de Estado de Educación y Universidades, Generalitat Valenciana under Project No. CTIDIA/2002/50, Spanish CICyT under Grant No. MAT2000-1047, Award No. Rec-005 of the U.S. Civilian Research and Development Foundation for the Independent States of the Former Soviet Union (CRDF). One of the authors (G.V.K.) thanks Spanish MCyT for her Ramon and Cajal Fellowship. The authors thank Professor V. O. Vas kovskiy for his help.García Miquel, ÁH.; Bhagat, S.; Lofland, S.; Kurlyandskaya, G.; Svalov, A. (2003). Ferromagnetic resonance in FeCoNi electroplated wires. Journal of Applied Physics. 94(3):1868-1872. https://doi.org/10.1063/1.1590407S18681872943Sixtus, K. J., & Tonks, L. (1932). Propagation of Large Barkhausen Discontinuities. II. Physical Review, 42(3), 419-435. doi:10.1103/physrev.42.419Panina, L. V., & Mohri, K. (1994). Magneto‐impedance effect in amorphous wires. Applied Physics Letters, 65(9), 1189-1191. doi:10.1063/1.112104Vázquez, M., & Hernando, A. (1996). A soft magnetic wire for sensor applications. Journal of Physics D: Applied Physics, 29(4), 939-949. doi:10.1088/0022-3727/29/4/001Britel, M. R., Ménard, D., Melo, L. G., Ciureanu, P., Yelon, A., Cochrane, R. W., … Cornut, B. (2000). Magnetoimpedance measurements of ferromagnetic resonance and antiresonance. Applied Physics Letters, 77(17), 2737-2739. doi:10.1063/1.1320042Garcı́a-Miquel, H., Garcı́a, J. ., Garcı́a-Beneytez, J. ., & Vázquez, M. (2001). Surface magnetic anisotropy in glass-coated amorphous microwires as determined from ferromagnetic resonance measurements. Journal of Magnetism and Magnetic Materials, 231(1), 38-44. doi:10.1016/s0304-8853(01)00040-3Wiggins, J., Srikanth, H., Wang, K.-Y., Spinu, L., & Tang, J. (2000). Magneto-impedance of glass-coated Fe–Ni–Cu microwires. Journal of Applied Physics, 87(9), 4810-4812. doi:10.1063/1.373167Pirota, K. ., Kraus, L., Chiriac, H., & Knobel, M. (2000). Magnetic properties and giant magnetoimpedance in a CoFeSiB glass-covered microwire. Journal of Magnetism and Magnetic Materials, 221(3), L243-L247. doi:10.1016/s0304-8853(00)00554-0Antonov, A. S., Buznikov, N. A., Iakubov, I. T., Lagarkov, A. N., & Rakhmanov, A. L. (2001). Nonlinear magnetization reversal of Co-based amorphous microwires induced by an ac current. Journal of Physics D: Applied Physics, 34(5), 752-757. doi:10.1088/0022-3727/34/5/314Gay-Balmaz, P., Maccio, C., & Martin, O. J. F. (2002). Microwire arrays with plasmonic response at microwave frequencies. Applied Physics Letters, 81(15), 2896-2898. doi:10.1063/1.1513663Beach, R. S., Smith, N., Platt, C. L., Jeffers, F., & Berkowitz, A. E. (1996). Magneto‐impedance effect in NiFe plated wire. Applied Physics Letters, 68(19), 2753-2755. doi:10.1063/1.115587Kurlyandskaya, G. V., Barandiarán, J. M., Gutiérrez, J., Garcı́a, D., Vázquez, M., & Vas’kovskiy, V. O. (1999). Magnetoimpedance effect in CoFeNi plated wire with ac field annealing destabilized domain structure. Journal of Applied Physics, 85(8), 5438-5440. doi:10.1063/1.369968Garcia, J. ., Asenjo, A., Sinnecker, J. ., & Vazquez, M. (2000). Correlation between GMI effect and domain structure in electrodeposited Co–P tubes. Journal of Magnetism and Magnetic Materials, 215-216, 352-354. doi:10.1016/s0304-8853(00)00156-6Yu, R. H., Landry, G., Li, Y. F., Basu, S., & Xiao, J. Q. (2000). Magneto-impedance effect in soft magnetic tubes. Journal of Applied Physics, 87(9), 4807-4809. doi:10.1063/1.373166Kurlyandskaya, G. ., Garcı́a-Miquel, H., Vázquez, M., Svalov, A. ., & Vas’kovskiy, V. . (2002). Longitudinal magnetic bistability of electroplated wires. Journal of Magnetism and Magnetic Materials, 249(1-2), 34-38. doi:10.1016/s0304-8853(02)00500-0Kurlyandskaya, G. V., Yakabchuk, H., Kisker, E., Bebenin, N. G., Garcı́a-Miquel, H., Vázquez, M., & Vas’kovskiy, V. O. (2001). Very large magnetoimpedance effect in FeCoNi ferromagnetic tubes with high order magnetic anisotropy. Journal of Applied Physics, 90(12), 6280-6286. doi:10.1063/1.1418423Favieres, C., Aroca, C., Sánchez, M. C., & Madurga, V. (2000). Matteucci effect as exhibited by cylindrical CoP amorphous multilayers. Journal of Applied Physics, 87(4), 1889-1898. doi:10.1063/1.372109Lofland, S. E., Garcia-Miquel, H., Vazquez, M., & Bhagat, S. M. (2002). Microwave magnetoabsorption in glass-coated amorphous microwires with radii close to skin depth. Journal of Applied Physics, 92(4), 2058-2063. doi:10.1063/1.149484

Thermal hysteresis of microwave loss in (La1-xPrx)(0.7)Ca 0.3MnO3 films

[EN] We have measured the temperature (T) dependencies of the dc resistances (R-dc) and the microwave loss (R-muw) in a variety of samples of (La1-xPrx)(0.7)Ca0.3MnO3 while varying x from 0 to 0.4. Whereas both the sets of data exhibit maxima, the ac loss peak is much flatter and, during cooling, appears at a much lower temperature than the peak temperature in R-dc. The discrepancy, which vanishes for x=0, increases with lowering tolerance factor (t) (or increasing x). Also R-muw vs T exhibits large thermal hysteresis for x=0.4 indicating that the transition is first order. Cooling in a magnetic field of 9 kOe causes an upward shift of about 20 K in the R-muw peak, in some of the x=0.4 films, yielding a large magnetoimpedance. Further, once these films are exposed to a magnetic field at low T, they fail to recover their virginal behavior on subsequent cooling from room T. These films could be brought to their original state by annealing at high T. The discrepancy between R-dc and R-muw implies that the system is inhomogeneous at low T, providing, for the first time, microwave absorption evidence that manganites exhibit multiphase behavior. Presumably, disorder and strain (increasing with x) combine to stabilize a mixed phase. (C) 2002 American Institute of Physics.S77367738911

Standing Spin Wave Resonances in Manganite Films

We report the first observation of spin wave resonances in 110 nm thick films of LBMO. The spin wave stiffness follows $D$ = 47 (1 - 3 \times 10$_{-7}$ $T^{5/2}$) meV${\AA_2}$.Comment: 5 pages LATEX, 3 figures available on request. Submitted to Nature. Please send all queries to [email protected]

Giant positive magnetoresistance in metallic VOx thin films

We report on giant positive magnetoresistance effect observed in VOx thin films, epitaxially grown on SrTiO3 substrate. The MR effect depends strongly on temperature and oxygen content and is anisotropic. At low temperatures its magnitude reaches 70% in a magnetic field of 5 T. Strong electron-electron interactions in the presence of strong disorder may qualitatively explain the results. An alternative explanation, related to a possible magnetic instability, is also discussed.Comment: 4 pages, 5 figures included in the text, references update

Large Second Harmonic Kerr rotation in GaFeO3 thin films on YSZ buffered Silicon

Epitaxial thin films of gallium iron oxide (GaFeO3) are grown on (001) silicon by pulsed laser deposition (PLD) using yttrium-stabilized zirconia (YSZ) buffer layer. The crystalline template buffer layer is in-situ PLD grown through the step of high temperature stripping of the intrinsic silicon surface oxide. The X-ray diffraction pattern shows c-axis orientation of YSZ and b-axis orientation of GaFeO3 on Si (100) substrate. The ferromagnetic transition temperature (TC ~ 215 K) is in good agreement with the bulk data. The films show a large nonlinear second harmonic Kerr rotation of ~15 degrees in the ferromagnetic state.Comment: 16 pages, 4 figures, To be published in J. Magn. Magn. Ma

Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

We report on the optical properties of undoped single crystal LaMnO_3, the parent compound of the colossal magneto-resistive manganites. Near-Normal incidence reflectance measurements are reported in the frequency range of 20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity, s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance data. The far-infrared spectrum of s_1(w) displays the infrared active optical phonons. We observe a shift of several of the phonon to high frequencies as the temperature is lowered through the Neel temperature of the sample (T_N = 137 K). The high-frequency s_1(w) is characterized by the onset of absorption near 1.5 eV. This energy has been identified as the threshold for optical transitions across the Jahn-Teller split e_g levels. The spectral weight of this feature increases in the low-temperature state. This implies a transfer of spectral weight from the UV to the visible associated with the paramagnetic to antiferromagnetic state. We discuss the results in terms of the double exchange processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure

Electrical transport, thermal transport, and elastic properties of M2AlC (M=Ti, Cr, Nb, and V)

Physical Review B: Condensed Matter and Materials Physics, 72(11): pp. 115120-1—115120-6. Retrieved September 19, 2006 from http://www.mse.drexel.edu/max/pdf%20references/drexel_pdfs/papers/2005/HettingerPRB%202005_NSF.pdf. DOI: http://dx.doi.org/10.1103/PhysRevB.72.115120In this paper we report on a systematic investigation, in the 5 to 300 K temperature regime, of the electronic, magnetotransport, thermoelectric, thermal, and elastic properties of four M2AlC phases: Ti2AlC, V2AlC, Cr2AlC, and Nb2AlC. The electrical conductivity, Hall coefficient, and magnetoresistances are analyzed within a two-band framework assuming a temperature-independent charge carrier concentration. As with other MAX-phase materials, these ternaries are nearly compensated, viz. the densities and mobilities of electrons and holes are almost equal. There is little correlation between the Seebeck and Hall coefficients. With Young’s and shear moduli in the 270 GPa and 120 GPa range, respectively, the phases studied herein are reasonably stiff. With room temperature thermal conductivities in the 25 W/m K range (45 W/m K for V2AlC) they are also good thermal conductors