Magneto-transport properties of two-dimensional Co anti-dot arrays

We fabricated two-dimensional Co anti-dot arrays, square-lattice structure of 1.02-μm-diameter circular holes with a periodicity of 1.60 μm, on a silicon substrate by using the CMOS (complementary metal-oxide semiconductor) process. The X-ray diffraction data indicate that the anti-dot arrays constitute an exchange-biased system that consists of vertical ferromagnetic Co layers interfaced with antiferromagnetic Co-oxide layers. We found an anomaly in the temperature dependence of the resistivity at temperatures below the Neel temperature of CoO. We also found exchange biased behaviors in both the magnetization curves and the magneto-transport data. By extracting the exchange-bias fields of the anti-dot array, we found that the exchange bias for the longitudinal magnetic field was much larger than that for the transverse field, which might be attributed to the spin-transfer effect.