  We study quantum Otto thermal machines with a two-spin working system coupled
by anisotropic interaction. Depending on the choice of different parameters,
the quantum Otto cycle can function as different thermal machines, including a
heat engine, refrigerator, accelerator and heater. We aim to investigate how
the anisotropy plays a fundamental role in the performance of the quantum Otto
engine operating in different time scales. We find that while the efficiency of
the engine efficiency increases with the increase in anisotropy for the
quasistatic operation, quantum internal friction and incomplete thermalization
degrade the performance in a finite time cycle. Further, we study the QOE with
one of the spins, the local spin, as the working system. We show that the
efficiency of such an engine can surpass the standard quantum Otto limit, along
with maximum power, thanks to the anisotropy. This can be attributed to quantum
interference effects. We demonstrate that the enhanced performance of a
local-spin QOE originates from the same interference effects, as in a
measurement-based QOE for their finite time operation.
