Leveraging 3d-4f Coordination: Molecular Quantum Spring-Magnet Behavior in Axial Ni₂Ln Complexes

Area of Science:

• Molecular Magnetism
• Coordination Chemistry
• Quantum Information Science

Background:

• Classical exchange spring magnets utilize hard and soft magnetic phases for enhanced performance.
• Designing molecular analogues requires precise control over magnetic interactions and anisotropy at the nanoscale.
• Heterometallic complexes offer a platform to integrate different magnetic ions and tailor their coupling.

Purpose of the Study:

• To synthesize and characterize heterotrimetallic 3d-4f complexes with a linear Ni-Ln-Ni core.
• To investigate the magnetic properties, including magnetic bistability and relaxation dynamics.
• To mimic the behavior of macroscopic exchange spring magnets at the molecular level.

Main Methods:

• Synthesis of Ni-Ln-Ni complexes with N3O3 ligand environments.
• Computational studies using CASSCF to determine anisotropy axes and electronic configurations.
• Magnetic characterization using DC, AC, and µSQUID magnetometry down to 30 mK.

Main Results:

• Isostructural Ni2Ln complexes were synthesized, with Ni2Tb, Ni2Dy, and Ni2Ho exhibiting slow magnetic relaxation and open hysteresis loops.
• Ferromagnetic 3d-4f coupling was observed in active systems, contrasting with fast relaxation in inactive analogues.
• Analysis revealed that Ni2+ ions act as the 'hard' phase and Ln3+ ions as the 'soft' phase, with their coupling enhancing magnetic performance.

Conclusions:

• Optimal 3d-4f coordination enables the design of molecular magnets with tunable relaxation and bistability.
• The studied complexes successfully mimic exchange spring magnet behavior at the molecular scale.
• These findings advance the development of molecular magnets for quantum information and nanoscale magnetic devices.