I. Characterization of Magnetic and Electrostatic Properties in Nanomaterials

My research is to understand the magnetic and electrostatic structures of nanomaterials using off-axis electron holography and Lorentz electron Microscopy. These instruments are very powerful tools for investigating magnetic structures in materials with nanometers size and have higher resolutions and more informations than microscopes such as a magnetic force microscope, a scanning hall probe microscope and a SQUID magnetic microscope. Since the magnetic behavior of nanomaterials is strongly related to size, distribution, chemistry crystallographic orientation of the materials, we examine the correlations between the magnetic and electrostatic properties and microstructures including chemistry. We will investigate the electrostatic structures of biased semiconductors, transistors, and nanomaterials by using a transmission electron microscope (TEM) with the special sample holder that allows to observe them in-situ during supplying a bias voltage to the samples. These studies will contribute to develop the new technologies for magnetic storages and transistors.

II. Relationships between Microstructures and Magnetic Properties in Minerals

In order to understand the magnetic acquisition mechanisms and the magnetic properties of rocks in nature, most studies of rock magnetisms has been carried out by only bulk measurements, nevertheless it is necessary to examine relationships between microstructures and magnetic properties in rocks for essential understanding of rock magnetisms. Especially, we study about effects of microstructure on magnetic properties of magnetite [Fe3O4] and the origin of remanent magnetization in an exsolved hematite-ilmenite [Fe2O3-FeTiO3] system by combination of conventional TEM including energy-filtered TEM, off-axis electron holography and Lorentz electron microscopy.

III. Minerals-Water-Microorganisms Interaction on the Earth Surface

It is known that the redistribution of elements on the Earth surface results from an interaction between minerals, water and atmosphere. Secondary minerals formed at an initial stage as a result of the interaction are mostly nanometer size mineral particles and clay minerals, which have their ability for adsorbing cations and anions because of a huge, charged surface area. Therefore, such a mineral is used widely as an effective absorbent for toxic metals to remediate or protect environments. Recent studies have revealed formations of these minerals are qualitatively related to the presence of microorganisms. My interest is to understand quantitatively effects of microorganisms on formations of mineral particles and migration of toxic elements. We study on weathering processes in the present day and the Precambrian age as well, which are the most important water-rocks (minerals) reaction on the Earth surface. The interest is that we may be able to know O2 and CO2 concentrations in the Precambrian age because the information of the Precambrian atmosphere was recorded in the rocks by their interaction.