Giant magnetroresistance properties of specular spin valve films in a current perpendicular to plane structure

Conventional and specular spin valve films in a current perpendicular to plane (CPP) structure have been investigated. The specular spin valve film with bottom type structure had two oxidized layers: one in the pinned layer, which was oxidized during an in situ deposition process, and the other in the free layer, which was a naturally oxidized Cu/Ta cap. Both films had increasing resistance, R, and resistance change, $\mathrm{\Delta R,}$ with decreasing element size. The conventional spin valve film showed a resistance times area product, RA, of 144 mΩ μm² and a resistance change area product, $\mathrm{\Delta RA,}$ of 0.7 mΩ μm² while the specular spin valve film showed RA of 1120 mΩ μm² and $\mathrm{\Delta RA}$ of 23 mΩ μm². The $\mathrm{\Delta RA}$ of the specular spin valve film was about 33 times larger than that of the conventional spin valve film. The calculated magnetoresistance (MR) ratios, ${\mathrm{MR}}_{\mathrm{SV}},$ of each spin valve film were 1.9% and 2.3%, respectively. We think oxidized layers in the spin valve film caused the specular electron scattering and this lengthened the path of the conduction electrons, enhancing the interfacial and bulk spin dependent scattering. We estimated the output voltage change of the 0.01 μm² element, the size required for 150 Gb/in.² recording density, of the specular spin valve film in CPP mode to be 5.3 mV. It was almost six times larger than that of the conventional spin valve film at constant power consumption. Specular spin valve film are advantageous for the CPP structure element for future giant MR sensors.