Celia Castán-Guerrero worked as a CNR-IOM Post-doc.
She has a background in nano- and micro-fabrication techniques (EBL, FIB, photolithography), as well as in magnetic characterization techniques, such as MOKE, Kerr microscopy, XPEEM and XMCD. Her actual field of research also includes in-operando experiments to investigate the properties of materials either under electric and magnetic fields or in near ambient conditions.
We present a new experimental setup for performing X-ray Absorption Spectroscopy (XAS) in the soft X-ray range at ambient pressure. The ambient pressure XAS setup is fully compatible with the ultra high vacuum environment of a synchrotron radiation spectroscopy beamline end station by means of ultrathin Si3N4 membranes acting as windows for the X-ray beam and seal of the atmospheric sample environment. The XAS detection is performed in total electron yield (TEY) mode by probing the drain current from the sample with a picoammeter. The high signal/noise ratio achievable in the TEY mode, combined with a continuous scanning of the X-ray energies, makes it possible recording XAS spectra in a few seconds. The first results show the performance of this setup to record fast XAS spectra from sample surfaces exposed at atmospheric pressure, even in the case of highly insulating samples. The use of a permanent magnet inside the reaction cell enables the measurement of X-ray magnetic circular dichroism at ambient pressure.
J. Phys.: Conf. Ser., 903, 012061, (2017)
Influence of Mn diffusion on IrMn thickness threshold for the onset of exchange bias in IrMn/Co bilayers
G. Vinai, L. Frangou, C. Castan-Guerrero, V. Bonanni, B. Gobaut, S. Auffret, I.L. Prejbeanu, B. Dieny, V. Baltz and P. Torelli
In this work, we studied the influence of the buffer layer composition on the IrMn thickness threshold for the onset of exchange bias in IrMn/Co bilayers. By means of magnetometry, x-ray absorption and x-ray photoelectron spectroscopy, we investigated the magnetic and chemical properties of the stacks. We demonstrated a higher diffusion of Mn through the Co layer in the case of a Cu buffer layer. This is consistent with the observation of larger IrMn thickness threshold for the onset of exchange bias.
AIP Advances, 5, 127128, (2015)
Magnetoresistance of galfenol-based magnetic tunnel junction
B. Gobaut, G. Vinai, C. Castan-Guerrero, D. Krizmancic, H. Rafaqat, S. Roddaro, G. Rossi, G. Panaccione, M. Eddrief, M. Marangolo, and P. Torelli
The manipulation of ferromagnetic layer magnetization via electrical pulse is driving an intense research due to the important applications that this result will have on memory devices and sensors. In this study we realized a magnetotunnel junction in which one layer is made of Galfenol (Fe1-xGax) which possesses one of the highest magnetostrictive coefficient known. The multilayer stack has been grown by molecular beam epitaxy and e-beam evaporation. Optical lithography and physical etching have been combined to obtain 20x20 micron sized pillars. The obtained structures show tunneling conductivity across the junction and a tunnel magnetoresistance (TMR) effect of up to 11.5% in amplitude.
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NFFA is a Progetto Internazionale financed by MIUR through CNR
(Istituto Officina dei Materiali, Trieste) and Elettra-Sincrotrone Trieste
and managed by the Commissione NFFA chaired by Giorgio Rossi
(Università di Milano and IOM-CNR).