Domain structures and temperature-dependent spin reorientation transitionsin c-axis oriented Co-Cr thin films

Highly c-axis oriented Co95Cr5 films with perpendicular anisotropy were gro wn epitaxially on Si (111), using an Ag seed layer, by physical vapor depos ition. Films were characterized by x-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction, and Lorentz microsco py in a TEM. The following epitaxial relationship was confirmed: (111)(Si)p arallel to(111)(Ag)parallel to(0001)(CoCr);[(2) over bar 20](Si)parallel to [(2) over bar 20](Ag)parallel to[(1) over bar 100](CoCr). Magnetic domain s tructures of these films were observed as a function of thickness; t, in th e range, 200 Angstrom < t < 700 Angstrom using a wedge-shaped sample, and t emperature-dependent measurements were carried out by in situ resistance he ating. Thickness was measured locally by electron energy loss spectroscopy. At room temperature, below a critical thickness, t(c)approximate to 300 An gstrom, the magnetization was found to be effectively in-plane of the film, and above t(c) a regular, stripe-like domain pattern with a significant, a lternating in sign, perpendicular component was observed. The spin reorient ation transitions of the stripe domains to the in-plane magnetization were studied dynamically by observing the domains as a function of temperature b y in situ heating up to 350 degrees C. The critical transition thickness, t (c), which is a function of K-u and magnetostatic energy, was found to incr ease with increasing temperature. The stripe-domain period, L observed at r oom temperature was found to increase gradually with thickness; L=90 nm at t=300 Angstrom, and L=110 nm at t=700 Angstrom. (C) 2000 American Institute of Physics. [S0021-8979(00)46408-X].