  We performed SQUID and FMR magnetometry experiments to clarify the
relationship between two reported magnetic exchange effects arising from
interfacial spin-polarized charge transfer within ferromagnetic metal
(FM)/molecule bilayers: the magnetic hardening effect, and
spinterface-stabilized molecular spin chains. To disentangle these effects,
both of which can affect the FM magnetization reversal, we tuned the metal
phthalocyanine molecule central site's magnetic moment to selectively enhance
or suppress the formation of spin chains within the molecular film. We find
that both effects are distinct, and additive. In the process, we 1) extended
the list of FM/molecule candidate pairs that are known to generate magnetic
exchange effects, 2) experimentally confirmed the predicted increase in
anisotropy upon molecular adsorption; and 3) showed that spin chains within the
molecular film can enhance magnetic exchange. This magnetic ordering within the
organic layer implies a structural ordering. Thus, by distengangling the
magnetic hardening and exchange bias contributions, our results confirm, as an
echo to progress regarding inorganic spintronic tunnelling, that the milestone
of spintronic tunnelling across structurally ordered organic barriers has been
reached through previous magnetotransport experiments. This paves the way for
solid-state devices studies that exploit the quantum physical properties of
spin chains, notably through external stimuli.
