Exchange anisotropy in coupled films of Ni81Fe19 with NiO and Co<i>x</i>Ni1−<i>x</i>O

Abstract

Shifted hysteresis loops were used to investigate exchange anisotropy in 500 Å CoxNi1−xO/300 Å Ni81Fe19 polycrystalline bilayer couples. Bilayers of Ni81Fe19 with NiO have a room-temperature exchange field, He, of 30 Oe in the as-deposited state. A maximum in the exchange field at room temperature was observed near x=0.4, indicating an optimal alloying of the properties of the high anisotropy CoO and the high Néel temperature NiO. The blocking temperatures of the exchange couples vary linearly with x, suggesting a linear dependence of the oxide Néel temperature with x.