Exchange Biasing Single Molecule Magnets: Coupling of TbPc₂ to Antiferromagnetic Layers

TLDR

We investigate the possibility of inducing exchange bias between single‑molecule magnets and metallic or oxide antiferromagnetic substrates. Element‑resolved X‑ray magnetic circular dichroism measurements were performed on TbPc₂ deposited on Mn and CoO layers. TbPc₂ on Mn shows exchange bias with a negative horizontal shift of the Tb magnetization loop after field cooling, whereas on CoO it displays paramagnetic loops with no bias, demonstrating that SMM can polarize pinned spins and enable metal‑organic exchange‑biased heterostructures.

Abstract

We investigate the possibility to induce exchange bias between single molecule magnets (SMM) and metallic or oxide antiferromagnetic substrates. Element-resolved X-ray magnetic circular dichroism measurements reveal, respectively, the presence and absence of unidirectional exchange anisotropy for TbPc(2) SMM deposited on antiferromagnetic Mn and CoO layers. TbPc(2) deposited on Mn thin films present magnetic hysteresis and a negative horizontal shift of the Tb magnetization loop after field cooling, consistent with the observation of pinned spins in the Mn layer coupled parallel to the Tb magnetic moment. Conversely, molecules deposited on CoO substrates present paramagnetic magnetization loops with no indication of exchange bias. These experiments demonstrate the ability of SMM to polarize the pinned uncompensated spins of an antiferromagnet during field-cooling and realize metal-organic exchange-biased heterostructures using antiferromagnetic pinning layers.