Coexistence of spin‐lattice relaxation and phonon‐bottleneck processes in Gd(III)‐phthlocyaninato triple‐decker complexes under highly diluted conditions

Gd 3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single molecule magnets (SMMs), although the Gd 3+ ion does not have strong magnetic anisotropy. To reveal the origin of slow magnetic relaxations of Gd 3+ complexes, we investigated the magnetic properties and heat capacity of two Gd 3+ -phthalocyaninato triple-decker complexes, one of which has intramolecular Gd 3+ -Gd 3+ interactions and the other does not. It was shown that the Gd 3+ -Gd 3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of Gd 3+ complexes into a large amount of diamagnetic Y 3+ complexes, underwent dual magnetic relaxations. From detailed dynamical magnetic analyses, the coexistence of spin-lattice relaxation and phonon bottleneck processes is the origin of dual magnetic relaxation processes.