CORRELATION BETWEEN MAGNETIC AND STRUCTURAL-PROPERTIES OF NI80FE20 SPUTTERED THIN-FILMS DEPOSITED ON CR AND TA BUFFER LAYERS

We studied the magnetic properties and structure of sputtered Ni80Fe20 films, on Si(100) substrates with either a Cr or Ta buffer. The films deposited on Ta buffers exhibit a very low coercive field (Hc approximate to 0.9 Oe), much smaller than those deposited on Cr buffers (Hc approximate to 2.5 Oe). Moreover, by transmission electron microscopy (both plane views and cross-sections), it was established that the Ta buffer induces a marked (111) perpendicular texture and a small lateral grain size (D approximate to 150 Angstrom). This is in strong contrast with the absence of any preferential orientation and the larger crystalite size (D approximate to 400 Angstrom) of the films deposited on Cr. The very low coercivity obtained on Ta buffers is tentatively explained considering that the film geometry, together with the induced texture, constrained the magnetization to lie in (111) crystallographic planes, which is shown to strongly suppress the possible sources of local anisotropy fluctuations.