Magnetic Domain structure study by Mössbauer magnetic scans in Al/Metglas 2605S2/Al trilayers

P. MENDOZA ZÉLIS; G. A. PASQUEVICH; P. S. MOSCON; E. C. PASSAMANI; F. H. SÁNCHEZ

Medellin

Conferencia; XIII Latin American Conference on the Applications of the Mössbauer Effect; 2012

Universidad de Antoquia

Recently we have devised and implemented the Mössbauer Magnetic Scan (MMS) technique. This application results in a method useful to selective study the instantaneous response of atomic magnetic moments in a sample subjected to a varying magnetic field. Nuclear resonant absorption, and therefore Mössbauer spectroscopy lines intensity, depend on the relative orientation between the gamma ray and the atomic probe magnetic moment direction. Then, the orientation of the atomic magnetic moment can be inferred from the line intensity. Therefore, recording the line intensity the 57Fe 14.4 keV gamma ray absorption at constant Doppler energies coincident with the spectral lines of the dipolar magnetic hyperfine interaction as function of the applied magnetic field (MMS experiment) is possible to study local and dynamic magnetic properties of the material. In thick samples, the absorber pattern reflects the polarization process undergone by the gamma beam along its path through the sample, as absorption occurs at a given spectral line energy. This pattern depends on the domain structure of the sample, therefore the MMS pattern also could retrieve information about some features of the domain structure dinamic. In this work we present the result obtained by MMS technique to study 20 um thick Amorphous Metglass 2605S2 alloy ribbons prepared by melt spinning, which were coated on both sides with 20 um aluminum by DC sputtering [3]. We have found that in this type of trilayers, important tensile or compressive stress appears on the individual layers at temperatures different from the sputtering one, due to the layers different thermal expansion coefficients. Due to the high magnetostriction of the amorphous phase, these stresses induce magnetoelastic anisotropy and modify the domain structure. In fact, at room temperature more than 80% of the magnetic moments are aligned perpendicularly to the sample plane, while in an uncoated amorphous ribbon the magnetization mostly lays on the ribbon plane. The trilayer composite becomes a very soft magnetic material: a 100 Oe magnetic field applied in the ribbon plane direction is enough to completely orient the magnetization in this plane. We have recorded the Mössbauer transmission at single Doppler energies corresponding to the absorption maxima of the 57Fe six (broad) line Mössbauer spectrum, each one as a function of the ac magnetic field applied. The frequency response was studied using a triangular Magnetic field wave, from 7 mHz to 80 kHz, and using amplitudes of 1100 y 65 Oe, respectively. [1] G. A. Pasquevich, P. Mendoza Zélis, F. H. Sánchez, M. B. Fernández van Raap, A. L. Veiga and N. Martinez, Physica B, 384, (2006) pp 348-350. [2] G. Pasquevich, Phd Tesis, Facultad de Ciencias Exactas, Universidad Nacional de la Plata, March 2008. [3] P. S. Moscon, E. C. Passamani, C. Larica, F. H. Sánchez and P. Mendoza Zélis. Journal of Physics D: Applied Physics, 41 (2008) 225004.