Kazuaki Ikarashi

Spin-valves with antiferromagnetic /spl alpha/-Fe/sub 2/O/sub 3/ layers

We report that the spin-valve films using the antiferromagnetic /spl alpha/-Fe/sub 2/O/sub 3/ layers show good MR response due to the coercivity difference in an as-deposited state and due to the unidirectional biasing field after magnetic annealing. Both the high coercivity and the biasing field of the pinned layer is caused by an exchange coupling. The obtained MR ratio of 6.1% is higher than those of the other spin-valves using Fe-Mn or Ni-Mn owing to the high resistivity of the /spl alpha/-Fe/sub 2/O/sub 3/. Further higher MR ratio of 10% is achieved by imposing 1 nm-thick Co layers at the Ni-Fe/Cu interfaces. It was found that the free layer coercivity of these spin-valves is smaller than that in the Co-Pt/Cu/Ni-Fe sandwiches having the similar high coercivity of the pinned layer. High thermal stability and corrosion resistance were also confirmed in the /spl alpha/-Fe/sub 2/O/sub 3/ spin-valves.

Structure and magnetic properties of bulk Fe-Al-Ga-P-C-B-Si glassy alloys in a ringed form prepared by copper mold casting

Structure and soft magnetic properties were investigated for a bulk glassy Fe/sub 70/Al/sub 5/Ga/sub 2/P/sub 10.05/C/sub 5.75/B/sub 4.6/Si/sub 2.6/ alloy in a ring shape form with an outer diameter of 10 mm, an inner diameter of 6 mm and a thickness of 1 mm prepared by copper mold casting. The bulk sample consisted of only a single amorphous phase. The supercooled liquid region, saturation magnetization, and Curie temperature for the bulk sample are about 60 K, 1.2 T, and 620 K, respectively, in agreement with that of the corresponding amorphous alloy ribbon, The maximum permeability and the coercivity for the bulk sample are about 110000 and 2.2 A/m. These good soft magnetic properties of the bulk glassy alloy are presumably due to a higher degree of structural homogeneity resulting from its high glass-forming-ability. Therefore, these excellent soft magnetic properties as well as the very high castability for the Fe-Al-Ga-P-C-B-Si glassy alloy allows us to expect that this glassy alloy will be used as an engineering magnetic material.