CeTi@C80: A tender single molecule magnet with electric and magnetic didipoles investigated with magnetometry and x-ray absorption spectroscopy

In endohedral fullerenes otherwise unstable atomic clusters can be stabilized. Here we investigate the electronic and magnetic properties of the dimetallic endohedral fullerene CeTi@C 80 , a molecular system encapsulating nominally trivalent cations of Ce and Ti within a C 80 carbon cage. Using low temperature magnetometry and temperature-dependent X-ray Absorption Spectroscopy (XAS) at the Ce M 4 , 5 -edge, we explore the magnetism and the orientation of the Ce–Ti endohedral unit. The magnetization measurements indicate ”tender” single-molecule magnetism with small hysteresis and a 3.3 μ B magnetic moment. The measured XA spectra of drop-cast molecules can be simulated with a ligand field of a didipole that consists of a C–Ti and an opposite Ce–C dipoles. They confirm trivalent Ce with a J z =5/2 ground state and random distribution of the Ce–Ti axes. Temperature-dependent XAS below room temperature shows minimal spectral change, indicating a thermally robust ground-state. These findings establish CeTi@C 80 as a stable electric and magnetic didipole single molecule magnet. • Single molecule magnetism of CeTi@C 80 above 2 K. • High J z ground state of Ce at low temperatures as established by magnetometry. • Stable Ce 4f J z = 5 / 2 ground state up to room temperature and isotropic Ce–Ti axis distribution in multilayers as established by Ce M 4 , 5 -edge X-ray Absorption Spectroscopy.