  Single-molecule magnets weakly coupled to two ferromagnetic leads act as
memory devices in electronic circuits---their response depends on history, not
just on the instantaneous applied voltage. We show that magnetic anisotropy
introduces a wide separation of timescales between fast and slow relaxation
processes in the system, which leads to a pronounced memory dependence in a
wide intermediate time regime. We study the response to a harmonically varying
bias voltage from slow to rapid driving within a master-equation approach. The
system is not purely memristive but shows a partially capacitive response on
short timescales. In the intermediate time regime the molecular spin can be
used as the state variable in a two-terminal molecular memory device.
