Although many magnetic materials have been developed so far, strong magnets available today contain rare elements, generate significant environmental loads, and are heavy. There is a growing demand for lighter magnetic materials to be used in vehicles and passenger jets, and so development of lightweight, rare-element-free magnets with lower environmental load is being pursued. As the IoT age is coming, there is an increasing need to integrate and mount magnetic devices, such as sensors and memories, together with semiconductor devices.

The researchers performed first‐principle calculations on Sn₂Nb₂O₇ and Sn₂Ta₂O₇, which are A₂B₂O₇-type (pyrochlore-type) oxide semiconductors. The calculations showed that a valence band with a very narrow energy spread (quasi-flat band) would appear. It was shown that if holes are introduced into the quasi-flat band of these materials, they will show stable ferromagnetism over a very wide range of hole concentrations. This magnetism is likely due to a very rare electronic state caused by non-magnetic elements such as tin and oxygen. Theoretical analysis by the researchers showed that the narrow energy spread is due to a geometric configuration of the pyrochlore lattice in which four oxygens form regular tetrahedrons and their vertices are shared to build the lattice.

The researchers predicted actual materials that exhibit a quasi-flat band. They will continue with their theoretical and experimental research.