Increasing the exchange-bias field of Ni_0.5Co_0.5O films by microstructural control

The exchange-bias field produced by antiferromagnetic monoxide films has been shown to scale with the density of uncompensated interfacial spins. The uncompensated spin density is inversely proportional to the interfacial grain diameter. Accordingly, we have prepared Ni0.5Co0.5O films in which the average interfacial grain diameter is small, but the grains are elongated, thus avoiding thermally activated fluctuations of the spin system associated with small grain volumes. The exchange-bias field remained inversely proportional to the interfacial grain diameter, and was increased to twice its previous maximum value without introducing significant thermal instability. © 1999 American Institute of Physics.