Development of functional interfaces in materials and its structural study with a use of high-resolution transmission electron microscopy.

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We established a reproducible method to create oxygen deficient EuO thin films whose Curie temperature is about 150K.It is essential to control the reaction kinetically, not thermodynamically, in order to make such a film. We also prepared a granular film where EuO clusters are dispersed in a ferromagnetic Fe matrix. This composite film exhibits non-saturating magnetization curve at 5K,indicating that the magnetic moments of EuO and Fe align non-colinearly.In addition, we synthesized non-equilibrium Fe-Eu alloy thin films by evaporation technique. Though the phase diagram of the system shows that Fe and Eu are immiscible even in the liquid state, our X-ray diffraction and transmission electron microscopy measurements indicated that they do form metastable alloys. The Fe-rich side of the alloy displays a ferrimagnetic character, while Eu-rich alloys exhibits a metamagnetic behavior. Longitudinal magnetoresistance of the latter has an irreversible positive component, while transverse magenetoresistance has a negative one. These transport behavior is thought to arise from breakdown of the helical order of Eu metal by the Fe impurity.