  We characterized the interfaces of heterostructures with different stack
sequences of La0.7Sr0.3MnO3/BiFeO3 (LSMO/BFO) and BFO/LSMO using TEM revealing
sharp and rough interfaces, respectively. Magnetometry and magnetoresistance
measurements do not show a detectable exchange bias coupling for the multistack
with sharp interface. Instead, the heterostructures with rough and chemically
intermixed interfaces exhibit a sizable exchange bias coupling. Furthermore, we
find a temperature-dependent irreversible magnetization behavior and an
exponential decay of coercive and exchange bias field with temperature
suggesting a possible spin-glass-like state at the interface of both stacks.
