MeV Si+ irradiation of Ni/Fe multilayers: structural, transport and magnetic properties

The modification of the structural, transport and magnetic properties of Fe (28 Angstrom)/Ni(85 Angstrom) multilayers on 1-MeV Si+ irradiation at low t emperature (77 K) has been studied as a function of dose, The as-deposited multilayers exhibit a strong Ni(111)/Fe(110) texture with sharp interfaces. Upon irradiation, progressive intermixing at the interfaces is clearly obs erved in the low-angle X-ray reflectivity and quantified by fitting the dat a with a standard optical model incorporating interface roughness, intermix ing and individual layer thickness fluctuations. Simultaneously, the averag e grain size gradually increases from similar to 170 to similar to 250 Angs trom with increasing ion dose up to 3 X 10(16) ions cm(-2). These changes l ead to an increase in the anisotropic magnetoresistance from similar to 1.4 % in the as-deposited sample to similar to 1.8% after irradiation with a do se of 10(16) ions cm(-2), and to the establishment of an in-plane easy axis for the magnetization. The effect of ion bombardment on the transport prop erties are explained using a model based on the Boltzmann equation incorpor ating the intermixing characteristics determined from the quantitative X-ra y analyses. (C) 2001 Elsevier Science B.V. All rights reserved.