Search

Relaxation of magnetization in endohedral metallofullerenes DySc2N@C80 is studied at different temperatures, in different magnetic fields, and in different molecular arrangements. Magnetization behavior and relaxation are analyzed for powder sample, and for DySc2N@C80 diluted in non-magnetic fullerene Lu3N@C80, adsorbed in voids of a metal–organic framework, and dispersed in a polymer. The magnetic field dependence and zero-field relaxation are also studied for single-crystals of DySc2N@C80 co-crystallized with Ni(II) octaethylporphyrin, as well as for the single crystal diluted with Lu3N@C80. Landau–Zener theory is applied to analyze quantum tunneling of magnetization in the crystals. The field dependence of relaxation rates revealed a dramatic dependence of the zero-field tunneling resonance width on the dilution and is explained with the help of an analysis of dipolar field distributions. AC magnetometry is used then to get access to the relaxation of magnetization in a broader temperature range, from 2 to 87 K. Finally, a theoretical framework describing the spin dynamics with dissipation is proposed to study magnetization relaxation phenomena in single molecule magnets.

Carbide clusterfullerene DyYTiC@C80-Ih with three different metal atoms in the endohedral cluster is obtained by arc-discharge synthesis with methane as reactive gas and is successfully isolated by HPLC. The compound shows single-molecule magnetism (SMM) with magnetic hysteresis below 8 K. The SMM properties of DyYTiC@C80 are compared to those of DySc2N@C80 and the influence of the central atom in the endohedral cluster is analyzed.

Magnetic properties of endohedral metallofullerenes with nitride clusters DySc(2)N and Dy(2)ScN and different carbon cages are studied by SQUID magnetometry. All molecules behave as single molecule magnets (SMMs) and exhibit magnetic hysteresis. It is found that the blocking temperature of magnetization and relaxation times strongly depend on the fullerene cage, with the C(80)-I(h) isomer offering the best SMM properties.

Encapsulation of lanthanides ions inside a carbon cage gives a variety of structures with very different magnetic properties, including single molecule magnetism (SMM). When other non-metal ions (N, S, O) are encapsulated as well, short distance between metal ions and negatively-charged non-metal ions creates large single-ion magnetic anisotropy of encapsulated lanthanides. In such clusterfullerene SMMs, very large barriers of the relaxation of magnetization can be achieved.[1] Encapsulation of only two metal atoms gives a possibility to create unique 3-center spin systems comprising large localized magnetic moments of lanthanide ions and an unpaired semi-delocalized spin on the metal-metal bonding orbital. In such a system, giant exchange interactions emerge and couple magnetic moments of individual spins into a giant superspin structure featuring unusually high blocking temperatures of magnetization.[2] Importantly, slow relaxation of magnetziatin is preserved even when fullerene-SMMs are deposited onto metal substrates, which usually has a dramatic deteriorating effect on SMMs. This contribution will present an overview of the recent developments in the magnetism of EMFs in bulk samples as well as in submonolayers deposited on metallic substartes.. References [1] D.S. Krylov, F. Liu, S.M. Avdoshenko, L. Spree, B. Weise, A. Waske, A.U.B. Wolter, B. Büchner, A.A. Popov, Record-high thermal barrier of the relaxation of magnetization in the nitride clusterfullerene Dy2ScN@C80-Ih , Chem. Commun., 53 (2017) 7901-7904. [2] F. Liu, D.S. Krylov, L. Spree, S.M. Avdoshenko, N.A. Samoylova, M. Rosenkranz, A. Kostanyan, T. Greber, A.U.B. Wolter, B. Büchner, A.A. Popov, Single molecule magnet with an unpaired electron trapped between two lanthanide ions inside a fullerene, Nat. Commun., 8 (2017) 16098.