PUB - Publikationen an der Universität Bielefeld

Thermally evaporated permalloy/copper (Py/Cu) multilayers were deposited onto quarts glass substrate, oxidised and etched Si wafers at room temperature and at 100 K. The samples were examined during an evaporation process by means of in-situ conductance measurements whereas magnetisation, A-my diffraction, atomic force microscopy and the cross section electron transmission microscopy were performed exsitu to characterise our samples. Only very small GMR effect was observed for samples deposited at R.T. and at 100 K. An absence of the antiferromagnetic coupling seems to result from the large interface roughness. Multilayers deposited at 100 A showed the existence of highly topological disordered alloy-like structure formed during deposition process. Introduction In contrast to sputtered (Ni80Fe20=Py)/Cu multilayers (MIs) [1,2] no GMR oscillatory behaviour has been noticed for evaporated samples as a function of Cu sublayer thickness [3]. The GMR effect for evaporated Py/Cu Mis was only observed in a post annealing state [3] whereas annealing of the sputtered Py/Cu Mis even at low temperatures can led to gradual degradation of the Interlayer coupling as well as of the GMR effect [2]. This strongly indicates the influence of the deposition technique on the interlayer coupling and on the chin effect in Py/Cu multilayers. In this contribution we present reasons why far evaporated Py/Cu multilayers no GMR effect is observed. We compare the morphology, surface topography and crystal structure of Py/Cu Mis deposited by evaporation at room temperature (R.T.) and at 100 K. Experimental The [Ni80Fe20/Cu](N) (N denotes a number of bilayers and N less than or equal to 30) Mts were evaporated in UHV system from Al2O3 crucibles onto different substrates (etched Si, oxidised Si wafers and a quarts glass) covered with Py or Cu buffer layers or without any buffer layer. Thickness of evaporated layers were controlled by a quartz micro-balance. The residual pressure in the vacuum chamber with liquid nitrogen baffle was 0.06 mPa. The deposition rate for both Py and Cu evaporated materials was about 0.01 nm/sec and the distance between crucibles and substrate holder was 50 cm. Thicknesses of Py (d(Py)) and Cu (d(Cu)) sublayers were changed in the range of 0.8 less than or equal to d(Py)(d(Cu))less than or equal to 2.5 nm. The surface topography and the crystal structure of the samples were examined ex-situ by atomic force microscopy (AFM), low-(LAXRD) and high angle X-ray diffraction (HAXRD) using Cu K-alpha radiation. The morphology of selected samples has been examined by means of the transmission electron microscopy of cross-section (TEM-CS). Conductance of the samples and their magnetoresistance were measured insitu during the deposition process with a pseudo-four point method. The magnetic properties of selected samples have been measured ex-situ at room temperature with a vibrating sample magnetometer (VSM) in-plane (i-p) and out-of-plane (o-p). Results and Discussion.