Interaction of Langmuir–Blodgett films of Mn12 single molecule magnets with superconducting micro-tracks and nano-SQUIDs†

Molecular magnets with large spin moments are promising spintronic materials. In this report we study the feasibility of integrating these molecules into the field of superconducting spintronics which essentially deals with the mutual interactions of magnetic and superconducting systems. In this regard we have done two separate experiments using the widely studied single molecule magnet (SMM) Mn₁₂-ac. By performing transport measurements on thin superconducting micro-tracks of Nb coated with a Langmuir–Blodgett film of the Mn₁₂-ac SMM, we show that the SMM film significantly enhances the vortex activation energy near the transition temperature. The SMM can, therefore, help tuning the operating conditions of superconducting transition edge sensors. In a separate experiment, a Langmuir–Blodgett film of the SMM was grown onto a superconducting Nb nano-SQUID to look for local changes in magnetization arising from the magnetization tunneling phenomenon in the SMM. We observe random jumps in the voltage across the nano-SQUID corresponding to changes in the magnetization state of the SMM near the SQUID loops, which were not observed in the nano-SQUID without the SMM. These experiments show that the large spin moment and the discrete relaxation of magnetization in molecular magnets can be utilized to generate measurable signals in superconducting spintronic devices.