Structural studies of GMR magnetic multilayers and spin-valves grown by DC sputtering

The structures and growth characteristics of sputtered GMR magnetic multilayers and spin-valves have been characterized using conventional and high resolution transmission electron microscopy (CTEM and HRTEM). The first part of this dissertation focused on the characterization of polycrystalline Cu/Py (permalloy™), Ag/Py, and Cu/CoZr spin-valves. For the Cu/Py spin-valves, structures with different Py thicknesses sputtered at different temperatures were examined. All of the spin-valves displayed polycrystalline structures with columnar grains. The grains grew on close packed planes ({lcub}111{rcub} in the bcc Nb contacts and {lcub}110{rcub} in the fcc Cu, FeMn, and Py spin-valve layers) taking up a near Kurdjumov-Sachs {lcub}111{rcub}_fcc//{lcub}110{rcub}_bcc;<110> _fcc//<111>_bcc orientation relationship. FFT analysis and HRTEM image simulations indicate that in some of the columnar grains, the Cu, FeMn, and Py regions take up non-equilibrium bcc structures, regardless of differences in layer thicknesses and sputtering temperatures. For the Ag/Py spin-valves, in addition to the expected polycrystalline morphology, in one instance an epitaxial single crystal Ag layer was discovered when the spin-valve was grown directly on a Si substrate. HREDS has shown that this single crystal (epitaxial) layer is likely composed of Ag and In in a 4:1 atomic ratio. In all of the other Ag/Py spin-valve samples, polycrystalline morphologies were consistently observed regardless of the substrate. For the Cu/CoZr spin-valves, CTEM observations of two spin-valves revealed that both samples are polycrystalline with columnar grains similar to the morphologies observed in Cu/Py and Ag/Py spin-valves.; The second part of this dissertation is focused on determining the correct parameters for growing a high quality Cu buffer layer on an epitaxial Nb contact. CTEM observations demonstrate that the quality of epitaxial growth of Cu buffer layers depends strongly on deposition temperatures and post annealing. High quality epitaxial Cu buffer layers were obtained when the Cu layer was grown at low temperatures (100°C and 150°C) without post annealing. Diffraction patterns of multilayers show that twin variants appear in epitaxial Cu and Py layers, consistent with electron backscatter patterns (EBSP) results from thick films. HRTEM images reveal that the Cu buffer layer grown at 150°C appears as twin variants with two stacking sequences of {lcub}111{rcub} fcc planes. A three-layer periodic contrast observed in the Py layer can be rationalized based on overlapped twins along [110] with {lcub}111{rcub} twin planes.