2019, Yang, W., Velkos, G., Liu, F., Sudarkova, S.M., Wang, Y., Zhuang, J., Zhang, H., Li, X., Zhang, X., Büchner, B., Avdoshenko, S.M., Popov, A.A., Chen, N.

A new class of single-molecule magnets (SMMs) based on Dy-oxide clusterfullerenes is synthesized. Three isomers of Dy2O@C82 with Cs(6), C3v(8), and C2v(9) cage symmetries are characterized by single-crystal X-ray diffraction, which shows that the endohedral Dy−(µ2-O)−Dy cluster has bent shape with very short Dy−O bonds. Dy2O@C82 isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage. The short Dy−O distances and the large negative charge of the oxide ion in Dy2O@C82 result in the very strong magnetic anisotropy of Dy ions. Their magnetic moments are aligned along the Dy−O bonds and are antiferromagnetically (AFM) coupled. At low temperatures, relaxation of magnetization in Dy2O@C82 proceeds via the ferromagnetically (FM)-coupled excited state, giving Arrhenius behavior with the effective barriers equal to the AFM-FM energy difference. The AFM-FM energy differences of 5.4–12.9 cm−1 in Dy2O@C82 are considerably larger than in SMMs with {Dy2O2} bridges, and the Dy∙∙∙Dy exchange coupling in Dy2O@C82 is the strongest among all dinuclear Dy SMMs with diamagnetic bridges. Dy-oxide clusterfullerenes provide a playground for the further tuning of molecular magnetism via variation of the size and shape of the fullerene cage.

2009, Rößler, S., Harikrishnan, S., Naveen Kumar, C.M., Bhat, H.L., Elizabeth, S., Rößler, U.K., Steglich, F., Wirth, S.

We report on the magnetic and electrical properties of Pr 0.6Sr 0.4MnO 3 single crystals. This compound undergoes a continuous paramagnetic-ferromagnetic transition with a Curie temperature T C301 K and a first-order structural transition at T S64 K. At T S, the magnetic susceptibility exhibits an abrupt jump, and a corresponding small hump is seen in the resistivity. The critical behavior of the static magnetization and the temperature dependence of the resistivity are consistent with the behavior expected for a nearly isotropic ferromagnet with short-range exchange belonging to the Heisenberg universality class. The magnetization (M-H) curves below T S are anomalous in that the virgin curve lies outside the subsequent M-H loops. The hysteretic structural transition at T S as well as the irreversible magnetization processes below T S can be explained by phase separation between a high-temperature orthorhombic and a low-temperature monoclinic ferromagnetic phase.

2019, Bastien, G., Roslova, M., Haghighi, M.H., Mehlawat, K., Hunger, J., Isaeva, A., Doert, T., Vojta, M., Büchner, B., Wolter, A.U.B.

Magnetic properties of the substitution series Ru1-xCrxCl3 were investigated to determine the evolution from the anisotropic Kitaev magnet α-RuCl3 with Jeff=1/2 magnetic Ru3+ ions to the isotropic Heisenberg magnet CrCl3 with S=3/2 magnetic Cr3+ ions. Magnetization measurements on single crystals revealed a reversal of the magnetic anisotropy under doping, which we argue to arise from the competition between anisotropic Kitaev and off-diagonal interactions on the Ru-Ru links and approximately isotropic Cr-Ru and isotropic Cr-Cr interactions. In addition, combined magnetization, ac susceptibility, and specific-heat measurements clearly show the destabilization of the long-range magnetic order of α-RuCl3 in favor of a spin-glass state of Ru1-xCrxCl3 for a low doping of x≤0.1. The corresponding freezing temperature as a function of Cr content shows a broad maximum around x ≤ 0.45.