Enhancement of magnetoresistance by inserted nano oxide layer in Mn-Ir bottom spin valve

Abstract

Summary form only given. High output signal and easy controlling of bias point are necessary to achieve 100 G/bit/sup 2/ magnetic areal density in magnetic recording technology. Specular spin valve in which the NOL enhance specular electron scattering and smooth interface were suggested as a new technology. In this paper, we studied effect of nano-oxide layer (NOL) formation at the interface between ferromagnetic layers and investigated chemical bonding of NOL. Si/Ta(5nm)/NiFe(3.5 nm)/Mn-Ir(6 nm)/CoFe(2 nm)/NOL/CoFe(2 nm)/Cu(2.5 nm)/Co-Fe(t nm)/Ta(2.5 nm) specular bottom spin valves were deposited on Si(100) substrate by auto-process magnetron sputtering. The base pressure was less than 3x 10/sup -8/ Torr. The samples were deposited under 5 mTorr. A NOL was formed in the load lock chamber by exposing to pure oxygen gas. Samples were annealed for 30 min at 200/spl deg/C under 3 kOe in-plane magnetic field in a vacuum furnace (1 x 10/sup -5/ Torr), followed by cooling to room temperature for 2 hour. The magnetoresistance (MR) and the exchange bias field (H..) increased from 7.8 and 247 without NOL to 10.2 % and 320 Oe with NOL, at t =40 nm, respectively Also the coupling field (H/sub f/) and sheet resistance (R/sub s/) decreased from 35 and 4.9 without NOL to 19 Oe and 4.67 Q/sq with NOL, respectively. In case of using NOL the decreased sheet resistance indicates that the probability of spin dependent scattering of conduction electrons is increased because electrons have long mean free path in the ferromagnetic layers. Improved magnetic properties of spin valve by inserted NOL are considered to be due to the specular effect. The values of rms, peak-to-valley and average roughness decreased from 1.46, 45.3 and 0.92 to 1.32, 15.5 and 0.81 nm, after O/sub 2/ exposure This indicates that the interface greatly smoother by NOL formation. This uniform interface reduce ferromagnetic static coupling between two ferromagnetic layers XPS results showed that NOL was constituted from about 31 % Fe/sub 2/O/sub 3/ and about 51 % FeO. And Co-oxide was negligible. TEM will be presented in more detail microstructure of specular spin valve.