Abstract
In this work we show that a magnon spin capacitor is realized at a junction between two exchange coupled ferromagnets. In this junction, the buildup of magnon spin over the junction is coupled to the difference in magnon chemical potential, realizing the magnon spin analogue of an electrical capacitor. We analyse the junction in detail by considering spin injection and detection from normal metal leads, the tunnelling current across the junction and magnon decay within the ferromagnet, showing that such a structure realizes a magnon spin RC circuit. Choosing platinum and yttrium iron garnet as the normal metal and ferromagnet, we numerically calculate the RC time, which ranges from picoseconds to microseconds, depending on the area of the junction. We therefore conclude that the magnon spin capacitor has clear experimental signatures and could directly be of use in applications.
