Ueda Laboratory

There are many kinds of magnetic materials around us, and they are used in various ways. Typical examples of them include motors used in electric vehicles, hard disks used to store big data, and AC transformers. These are materials called ferromagnets, as they are magnetized in the absence of a magnetic field, and they are intensely studied to improve their properties. While, most of magnetic materials are so-called antiferromagnets, in which the magnetic moment does not point in just one direction.
Quantum mechanical effects are important for the manifestation of magnetism. Although the quantum mechanical state of ferromagnets is relatively simple, there origin is not clarified yet. Furthermore, the quantum mechanical state of antiferromagnets cannot be fully described, and basic research is being conducted to elucidate these quantum states. In our laboratory, we aim to clarify the magnetic state and its origin in magnetic materials by developing new materials and growing single crystals, thereby establishing the fundamental theory of magnetic materials. For our purpose, when a magnetic material with a specific structure is not reported, it is necessary to create such a material, and we mainly use ordering of ions to develop new materials. In addition, since single crystal research is essential to clarify the details of magnetism, we are also focusing on single crystal growth.
Various quantum mechanical effects play crucial roles in the magnetic state of a magnetic material. First, even for a single magnetic ion, it is necessary to consider hybridization of multiple electron configurations. For conducting magnetic materials, the effects of conduction electrons and the magnetism of the conduction electrons themselves must be taken into account. Finally, quantum mechanical magnetic states are formed by the coupling of a macroscopic number of magnetic moments through interactions between the magnetic moments of magnetic ions. We mainly study localized magnetic materials, in which the influence of conduction electrons among the above effects can be ignored.