Pseudomorphic Growth of Fcc FeMn Thin Film on NiFe and its Interfacial Structure

Abstract

ABSTRACTThin film couple of NiFe/FeMn has been used in the magnetoresistive read head design in the magnetic recording industry. The strong magnetic coupling between FeMn and NiFe is of most importance in providing the stability of the MR head. FeMn has been shown to grow epitaxially on NiFe surface and form a metastable fcc structure. The existence of this fcc structure is believed to be the source of the magnetic coupling. It has also been shown that the grain to grain epitaxy exists in this polycrystalline thin film couple, however with only indirect evidence such as Moiré fringes across the interface boundary. To further study this pseudomorphic growth phenomenon, a specially prepared large grain FeMn/NiFe thin film couple was used. Lattice imaging of the interfacial structure was obtained by high resolution cross-section transmission electron microscopy. The plan-view TEM imaging and electron dilfraction patterns also show clear evidence of the grain to grain epitaxy in almost all the grains. The epitaxial strain associated with each coupled grain was also evidenced by the isolated strain contours within each grain. Detailed interfacial structure analysis will be given to elucidate the mechanism(s) by which the interfacial strain is accommodated.