Optimal diamagnetic dilution concentration for suppressing the dipole-dipole interaction in single-ion magnets

• Published in: Dalton transactions : an international journal of inorganic chemistry 2020-02, Vol.49 (7), p.2159-2167
• Main Authors: Hu, Zhao-Bo, Feng, Xin, Li, Jing, Zhang, Yi-Quan, Yin, Lei, Wang, Zhenxing, Ouyang, Zhongwen, Kurmoo, Mohamedally, Song, You
• Format: Article
• Language: English
• Subjects: Crystal structure; Crystallography; Diamagnetism; Dilution; Dipole interactions; Electron spin; Magnetic induction; Magnetic permeability; Magnetic relaxation; Magnetism; Magnets; Mathematical analysis; Optimization; Single crystals; Solid solutions
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt04403e

The effect of screening the Co II moment of monomeric [Co II L 2 (H 2 O)] (L = 8-hydroxyquinaldine), having a trigonal bipyramid coordination, by diamagnetic Zn in Co x Zn 1− x solid solutions on its magnetic relaxation was explored using ac-susceptibility, high-field electron-spin-resonance measurements and CASPT2 calculations. The retention of the crystal structure for all the solid solutions was demonstrated using single crystal diffraction. The dc-magnetization and theoretical fittings of the susceptibility for Co 1 and Co 0.1 Zn 0.9 gave a large zero-field-splitting (ZFS) D of 50 ± 6 cm −1 , and very weak dipole interaction between the nearest neighbors, while EPR and calculations confirmed the positive sign of the axial component ( D ). Consistent parameters were obtained from experiments and theory. Importantly, only field-induced relaxation was observed for the samples with less than 50% Co and a gradual change in the barrier energy to moment reversal and relaxation times was observed between 11% and 20% Co, while both were enhanced for higher dilutions. The results establish a clear barrier for extending the longevity of the magnetism for this type of single-ion species by lowering the intramolecular interactions. The results suggest that the magnetic interaction persists up to the second sphere, that is, for a dilution of 1 in 9 (11% Co). Importantly, this method is applicable to all single-ion magnet systems, that is, the optimum dilution concentration to restrain the dipole field can be given only by the single crystal structure. The relationship of magnetic properties and diamagnetic dilution has been studied for five-coordinate Co( ii ) complex. It is found that the optimal dilution concentration to restrain dipole field can be given only by the single crystal structure.