Abstract
We theoretically study the magnetization inside a normal metal induced in an -wave superconductor/ferromagnetic metal/normal metal/ferromagnetic metal/-wave superconductor Josephson junction. Using the quasiclassical Green's function method, we show that the magnetization becomes finite inside the . The origin of this magnetization is due to odd-frequency spin-triplet Cooper pairs formed by electrons of equal and opposite spins, which are induced by the proximity effect in the junction. We find that the magnetization in the can be decomposed into two parts, , where is the superconducting phase difference between the two and is the thickness of . The -independent magnetization exists generally in junctions, while carries all dependence and represents the fingerprint of the phase coherence between the two in Josephson junctions. The dependence thus allows us to control the magnetization in the by tuning for a fixed . We show that the -independent magnetization weakly decreases with increasing , while the -dependent magnetization rapidly decays with . Moreover, we find that the time-averaged magnetization exhibits a discontinuous peak at each resonance dc voltage : integer) when dc voltage as well as ac voltage with frequency are both applied to the junction. This is because oscillates generally in time (ac magnetization) with and thus , but can be converted into the time-independent dc magnetization for the dc voltage at . We also discuss that the magnetization induced in the can be measurably large in realistic systems. Therefore, the measurement of the induced magnetization serves as an alternative way to detect the phase coherence between the two in Josephson junctions. Our results also provide a basic concept for tunable magnetization in superconducting spintronics devices.
5 More- Received 3 April 2015
- Revised 3 June 2015
DOI:https://doi.org/10.1103/PhysRevB.92.024512
©2015 American Physical Society