磁性金屬與氧化物薄膜之介面研究-透過電場操控磁性材料

The control of magnetism using electric field has long been a crucial and challenging issue in fundamental physics and applications. Recently, the electrical control of magnetic properties has been shown to be more and more practicable. For example, in multiferroic materials, the magnetic domains and electric domains are strongly coupled. Besides, instead of a complex multiferroic oxide layer, the combination of a ferromagnetic thin film with a simple oxide layer, like MgO and etc, provides another big chance for the modulation of the magnetic properties using electric filed, because the applied electric filed will induce the net charges/electric dipoles at each sides of the oxide layer. With a ferroelectric oxide layer, the electrical control might be even easier. Due to the nonzero electrical remanence state, only a single pulse of electric field, instead of a continuous electric field for general oxide, is enough to switch the interface electrical dipoles, as well as the magnetic properties. Moreover, if the oxide layer is piezoelectric, the electrical field may induce the lattice expansion/compression in the oxide layer and the adjacent magnetic film. Accordingly the magnetism can be changed through the magneto-elastic effect. The above ideas clearly exhibit the novelty and application potential in the various hetero structures of magnetic metal/functional oxide. In this proposal, we are planning to setup a pulse-laser-deposition (PLD) system for the growth of oxide layer, combined with a multi-functional ultrahigh vacuum (UHV) chamber. With the combination of PLD to the conventional surface and magnetism instruments, including LEED, AES, MOKE and STM, we hope to in situ study the interface properties of magnetic metal/oxide in more details, especially the influence induced by electric field. Four kinds of sample listed in the following will be systematically investigated. (1) Magnetic metal/general oxide layer. (2) Magnetic metal/ferroelectric oxide layer. (3) Magnetic metal/ferromagnetic oxide layer. (4) Magnetic metal/piezoelectric oxide layer. Actually we observed fruitful exciting results from these systems, which can be widely applied in electrical control of magnetic devices.