Perpendicular Magnetoresistance of Microstructured Pillars in Fe/Cr Magnetic Multilayers
- PDF / 1,208,063 Bytes
- 11 Pages / 420.48 x 639 pts Page_size
- 8 Downloads / 196 Views
PERPENDICULAR MAGNETORESISTANCE OF MICROSTRUCTURED PILLARS IN Fe/Cr MAGNETIC MULTILAYERS M.A.M. GIJS - , S.K.J. LENCZOWSKI -- AND J.B. GIESBERS * Philips Research Laboratories, 5600 JA Eindhoven, The Netherlands Eindhoven University of Technology, Department of Physics, 5600 MB Eindhoven, The Netherlands
ABSTRACT We have fabricated pillar-like microstructures of high vacuum sputtered Fe/Cr magnetic multilayers and measured the giant magnetoresistance effect in the configuration where the measuring current is perpendicular to the film plane from 4.2 K to 300 K. At 4.2 K we find a magnetoresistance of 108 % for multilayers with a Fe thickness of 3 nm and a Cr thickness of 1 nm. The pronounced temperature dependence of the perpendicular magnetoresistance is studied for samples with different Cr thicknesses and tentatively explained by electron-magnon scattering. The low-temperature data are compared with existing low-temperature models.
INTRODUCTION Since the discovery of the giant magnetoresistance (MR) effect in magnetic multilayers [1], numerous studies on a variety of multilayer systems have been reported (e.g. [2, 3]). In practically all these experiments, the measuring current is in the plane of the multilayer, the so-called current-in-plane (CIP) geometry. Nevertheless, the great importance of experiments with the measuring current perpendicular to the multilayer plane (the socalled CPP-geometry) has been emphasized in several theoretical papers (4, 5, 6, 7, 8, 9]. All these theories are valid only at low temperatures and predict a considerably larger MR effect for the CPP geometry than for the CIP geometry. The first experiments on the CPP-MR were done for Co/Ag and Co/Cu multilayers [10]. In these experiments no microfabrication techniques were used; the multilayer was sandwiched between a superconducting Nb top and bottom contact electrode and the very small multilayer resistance (typically 0.01-0.1 pfl) was measured at 4.2 K using an ultra-sensitive SQUID-based system. This implies that measurements are only possible at liquid helium temperatures. Initially relatively weak magnetic fields (H < 40 kA/m) were applied; in an improved experimental setup it is now possible to use this experimental method in external fields up to several 1000 kA/m [11]. The CPP-MR of the strongly antiferromagnetically (AF) coupled Fe/Cr system (switching fields of typically 400 kA/m [12]), which is optimally suited for comparison with existing low-temperature models, was only measured quite recently by us using microstructured samples [13]. At the same time, these experiments provided the first data on the temperature dependence of the CPP-MR effect, which still represents a theoretical challenge. In particular the role of spin-flip scattering on the giant MR remains to be elucidated. Here, we will discuss our experiments on the low-temperature CPP-MR and on the temperature dependence of the CPP-MR of microstructured Fe/Cr multilayers. Pillar structures a few microns in size were fabricated using optical lithography and reactiv
Data Loading...
