Exchange coupling and magnetoresistance in Co/Ir multilayers prepared by ion beam sputtering

A series of Co/Ir multilayers has been prepared by Ion Beam Sputtering on a glass substrate covered by a Fe(10 nm)/Ir(10 nm) buffer layer. The Co thickness has been fixed at 3 nm and the Ir thickness varied between 0.1 and 2.4 nm. X-ray diffraction patterns performed on these multilayers show an fee structure with a (111) preferential texture. The antiferromagnetic (AFM) exchange coupling and magnetoresistance show an oscillating behavior as a function of the Ir thickness with a period of about 1 nm. The first AFM peak has been observed at the 0.6 nm thick Ir spacer layer and its strength corresponds to J(AF) = -6 erg/cm(2) at 4.2 It. This interlayer coupling is strong and is supported by ab initio calculations of the magnetization. Very strong variation of the exchange coupling has been observed between room temperature and 4.2 K and is attributed to the strong intermixing at the Cc/Ir interfaces.