The structural and magnetic phase transition in FeRh thin films are investigated. The ͑001͒ oriented single crystal FeRh thin films fabricated onto MgO ͑100͒ substrate possess lattice parameter a smaller than c, because of the compressive stress along the a axis from MgO substrate. With increasing annealing temperature, paramagnetic FeRh thin films transform into ferromagnetic and then antiferromagnetic-ferromagnetic ͑AF-FM͒ stages. The transition temperature of AF-FM increases with annealing temperature, while the thermal hysteresis width decreases. The M-H loops of the film annealed at 700°C show an opening at high magnetic fields during the transition state. Note that the opening in M-H loops disappears when AF phase has transformed into FM phase. The origin of the opening is not known but possibly due to the combination of hysteresis loops of FM and AF phases, where FM phase is soft magnetic and the AF phase FeRh shows a hysteresis behavior with coercivity due to the reduction of magnetic anisotropy at high temperatures. The abrupt change of coercivity along the perpendicular direction during the AF-FM transition suggests that a stress-induced magnetic anisotropy exists in FeRh thin films due to the volume expansion in the phase transition process.

Au nanoparticles dispersed SiO2-TiO2 composite films have been prepared by a novel wet process, Liquid Phase Deposition (LPD) method. The composite films were characterized by XRD, XPS, TEM, ICP, SEM and UV-VIS absorption spectroscopy. The results showed that the SiO2-TiO2 composite films containing Au III and Au I ionic species were co-deposited from a mixed solution of ammonium silicofluoride, ammonium hexafluorotitanate, boric acid and tetrachloroauric acid. The heat treatment induced the reduction of Au ions and formation of Au nanoparticles in the film. TEM observation revealed that the Au nanoparticles with 5-10 nm in diameter were found to be dispersed uniformly in the SiO2-TiO2 matrix. The optical absorption band due to the surface plasmon resonance of dispersed Au particles were observed at the wavelength of 550 nm and shifted toward longer wavelength with increasing heat treatment temperature.

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The magnetic and structural properties of FexRh100−x (x=35–80) nanoparticles fabricated by a solution phase chemical method have been studied systematically. From x-ray diffraction results, as-deposited nanoparticles of FeRh reveal a chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. The high-resolution transmission electron microscopy observations of FeRh nanoparticles indicate that the average size of 3–5nm in as-deposited state and larger size (10–15nm) particles are also distributed in the annealed sate. Nanoparticles with x=35–55 exhibit the behaviors of magnetization with temperature, which suggests the transition from the AFM to FM phases at around 100–200°C, whereas those with x=80 do very little change of magnetization with temperature. It is also found that there seems an effect of applied magnetic field on transition, that is, the transition temperature is shifted to a lower side upon the application of magnetic field during the transition process.

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