Mossbauer study of the influence of thermal treatment on giant magnetoresistance and interface structure in Fe/Cr multilayers

The dependence of the giant magnetoresistance effect (GMR) on the interface structure in Fe/Cr multilayers was studied by magnetoresistivity and Mossb auer spectroscopy. The Fe/Cr multilayers consisting of Fe(6 nm) + [Cr(1.1 n m)/Fe(3 nm)](60) + Cr(1.1 nm) were deposited by dc magnetron sputtering. Sa mples were annealed for 1 h at temperatures ranging from 200 to 500 degrees C. The interface structure was characterized by conversion electron Mossba uer spectroscopy (CEMS). Various different Fe sites: the bulk, step and per fect interface positions were identified. The evolution of the fraction of Fe atoms in different environments vs annealing temperature revealed that a nnealing at 300 degrees C induces bulk and in-plane diffusion of atoms. Hig her annealing temperature causes substantial roughening of the interface re lated to a strong bulk diffusion of atoms. Microstructural changes observed in the CEMS spectra correspond well to the GMR measurements which reveal a n enhancement of magnetoresistivity in Fe/Cr multilayers annealed at about 300 degrees C and its decrease due to deterioration of the interface at hig her annealing temperatures. (C) 1999 American Institute of Physics. [S0021- 8979(99)19608-7].