  The exchange bias effect is an essential component of magnetic memory and
spintronic devices. Whereas recent research has shown that anisotropies
perpendicular to the device plane provide superior stability against thermal
noise, it has proven remarkably difficult to realize perpendicular exchange
bias in thin-film structures. Here we demonstrate a strong perpendicular
exchange bias effect in heterostructures of the quasi-two-dimensional canted
antiferromagnet La$_2$CuO$_4$ and ferromagnetic (La,Sr)MnO$_3$ synthesized by
ozone-assisted molecular beam epitaxy. The magnitude of this effect can be
controlled via the doping level of the cuprate layers. Canted
antiferromagnetism of layered oxides is thus a new and potentially powerful
source of uniaxial anisotropy in magnetic devices.
