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Update(MM/DD/YYYY):10/21/2019

Prediction of Magnetic Materials Containing No Magnetic Elements


Researchers: Hase Izumi, Senior Researcher, Yanagisawa Takashi, Chief Senior Researcher, and Aiura Yoshihiro, Leader, Electronics and Photonics Research Institute

Summary

The researchers have theoretically predicted that if holes are introduced in an oxide represented by the chemical formula A2B2O7 that contains no magnetic elements, the oxide will exhibit magnetism.

Figure
(a) Pyrochlore lattice and (b) energy bands of Sn2Nb2O7
The red band of (b), which is called as a quasi-flat band, plays an essential role to become ferromagnetic


Background

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.

New findings

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.

Future plans

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






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