Double-decker phthalocyanine complexes with Tb3+ or Dy3+ showed slow magnetization relaxation as a single-molecular property. The temperature ranges in which the behavior was observed were far higher than that of the transition-metal-cluster single-molecule magnets (SMMs). The significant temperature rise results from a mechanism in the relaxation process different from that in the transition-metal-cluster SMMs. The effective energy barrier for reversal of the magnetic moment is determined by the ligand field around a lanthanide ion, which gives the lowest degenerate substate a large |Jz| value and large energy separations from the rest of the substates in the ground-state multiplets.

Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with theconcentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.

Alternating current (ac) magnetic susceptibility and magnetization hysteresis loop measurements have been carried out for anionic bis(phthalocyaninato)terbium and bis(phthalocyaninato)dysprosium. The two mononuclear lanthanide complexes show the characteristic temperature and frequency dependence in the ac susceptibility signals, reflecting their slow magnetization relaxation. From the Arrhenius analysis of the ac susceptibility data obtained for a diluted sample in a diamagnetic matrix, it has been found that the magnetization relaxation in the Tb complex is dominated by the two-phonon Orbach process in the temperature range 25−40 K and direct or Raman process below 25 K. In the Dy complex case, the Orbach process is the main relaxation process in the range 3−12 K. The Δ values in the Orbach term, corresponding to the height of the potential energy barrier to magnetic moment reversal, are in good agreement with the energy differences between the lowest and second lowest substates of the ground multiplet in the two cases. In the magnetization−field (M − H) loop measurements at 1.7 K, clear hysteresis has been observed for both complexes. These results indicate that the two double-decker phthalocyanine−lanthanide complexes behave as magnets at the single-molecular level. They are the first lanthanide compounds as well as the first mononuclear complexes showing such behaviors. Differences in the magnetization relaxation mechanism between the new “mononuclear lanthanide magnets” and the transition-metal-cluster-based SMMs (single-molecule magnets) are discussed.

We report on the magnetic properties of an oxide-diluted magnetic semiconductor (DMS), Zn0.64Mn0.36O. The temperature dependence of the magnetization shows a spin-glass behavior with the large magnitude of the Curie–Weiss temperature, corresponding to a stronger antiferromagnetic exchange coupling than other II–VI DMSs. The small effective Mn moment (x̄∼0.02) under high field also represents a strong antiferromagnetic exchange coupling in this compound.