We electrochemically synthesized film-type vanadium hexacyanochromate-based magnets with high critical temperatures (T c ): K I 0.31 V II 0.49 V III 0.51 [Cr III (CN) 6 ] 0.94 ‚6.5H 2 O (1) (T c ) 310 K) and K I 0.61 V II 0.97 V III 0.03 [Cr III (CN) 6 ] 0.88 ‚ 7.2H 2 O‚0.4C 2 H 5 OH (2) (T c ) 345 K). The colors of these films were blue and dark blue. For film 1, the Faraday ellipticity (FE) spectra showed a weak negative peak (A) and a strong negative peak (B) around 550 nm (-640 deg cm -1 at 50 K) and 660 nm (-2300 deg cm -1 at 50 K), respectively. In the Faraday rotation (FR) spectra, two dispersive-shaped lines were observed at the same wavelength. Simulation of these spectra showed that the observed spectra can be classified as the paramagnetic type of Faraday effects. For film 2, the Faraday effect was observed even above room temperature. In its FE spectra, two negative peaks were observed around 530 nm (-850 deg cm -1 at 50 K) and 660 nm (-300 deg cm -1 at 50 K), respectively. These FE peak positions are close to the peak positions of A and B for film 1, suggesting that the origins of the Faraday effects of 1 and 2 are the same. Based on stoichiometric coefficients of the obtained films, A and B bands were assigned to the intervalence transfer (IT) bands of V II -NC-Cr III and V III -NC-Cr III , respectively. The present Faraday spectra in the ferromagnetic region are the first to be observed among molecular-based magnets.

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Co x Pt 100−x nanoparticles with dimensions from approximately 2 to 5 nm were synthesized using the reverse micelle method. High-resolution electron microscopy revealed single- and poly-crystalline nanoparticle structures. Twin boundary is a common feature in the polycrystals. As-grown nanoparticles did not show any coercivity at room temperature. However, the nanoparticles became ferromagnetic after annealing at 550 °C for 4 h. Face-centered-cubic to face-centered-tetragonal phase transformation of the nanoparticles that occurred at annealing temperatures above 550 °C was confirmed by electron diffraction patterns and x-ray diffractometry. Coercivity of the annealed nanoparticles were found depending on the nanoparticle chemical compositions. Composition atomic ratio of Co to Pt at around unity gives the highest coercivity of 5500 Oe at room temperature.

Monodispersive FePt nanoparticle films can be stabilized firmly on rigid Si substrates using amino-functional silane, such as [3-(2-aminoethlyamino) propyl]trimethoxysilane, as a coupling layer. The Si substrate/SiO2/APTS/FePt nanoparticles heterostructure was confirmed using high-resolution electron microscopy (HREM). The HREM result agreed well with the x-ray reflectivity measurement upon the individual layer thickness. The as-made superparamagnetic FePt nanoparticle film transformed from chemically disordered fcc structure to chemically ordered L10 phase upon annealing at 800 °C for 30 min under a vacuum of 10−8 Torr. Plan-view high-resolution scanning electron microscopy (HRSEM) observation indicated that under high-vacuum annealing, coalescence of the monodispersive nanoparticle film was not significant. The HRSEM result was consistent with the in-plane x-ray diffractometry measurement, in which sharpening of the diffraction peaks occurred only very slightly for the annealed films.