14:45 〜 15:00
▼ [20p-D104-7] Analysis of spin switching effect in GdN/NbN/GdN superconducting spin valves
キーワード：Spin switching effect, Superconductor
Superconducting spin valves (SSVs)1,2 consisting of a superconductor spacer sandwiched by two ferromagnetic insulators (FIs) attract considerable interest since the superconducting state can be manipulated by the relative magnetization configuration of the FI layers. This means that the infinite magnetoresistance ratio can actually be achieved in SSVs. This phenomenon, referred to as spin switching effect (SSE), is caused by the induced exchange field in the SC spacer from the adjacent FI layers and thus the interfaces between SC/FIs are very important. SSVs with a NbN spacer have the potential to exhibit SSE at relatively high temperatures,3 owing to high critical temperature (TC) of 16 K of NbN. Our group has demonstrated the first, perfect SSEs in GdN/NbN/GdN trilayer SSVs by atomic level optimization of the two interfaces, however, the observation temperature remained as low as 1.3 K4. In this talk, to clarify optimum interfaces for SSE, we quantitatively analyzed the induced exchange field in the SSVs using different two models and compare it to the interfacial magnetic moment evaluated from polarized neutron reflectivity (PNR) measurements.
SSVs of GdN(27nm)/NbN(3.5nm)/GdN(13nm) trilayers were formed with the reactive sputtering technique in a UHV system. The Gd monolayers were inserted between NbN/GdN interfaces to compensate the nitrogen less interfaces. SSE signals were clearly observed from 2.5 K down to 1.1 K. The anti-parallel (AP) state showed a TC of 1.7 K while in the parallel (P) state it was 1.4 K. An equivalent induced magnetic field was quantitatively estimated by the Kulic-Endres modelf. A pair breaking factor in the model which was evaluated from a ration ofTC in the P and AP states was enhanced by hundredfold by tailoring interfaces by the Gd insertion layers. In our presentation, we will discuss a relationship between pair breaking factors and interfacial magnetic moments analyzed by PNR.
This work was supported by NSF and ONR grants, JSPS, and Fundacion Seneca (19791/PD/15). The research conducted at the SNS is sponsored by the Scientific User Facilities Division, Office of BES, U.S. DOE.
References
1P.G. De Gennes, Phys. Lett. 23, 10 (1966).
2B. Li, N. Roschewsky, B.A. Assaf, M. Eich, M. Epstein-Martin, D. Heiman, M. Muzenberg, and J.S. Moodera, Phys. Rev. Lett. 110, 97001 (2013).
3Y. Zhu, A. Pal, M.G. Blamire, and Z.H. Barber, Nat. Mater. 16, 195 (2017).
4Y. Takamura et al., MMM conf., Pittsburgh, USA, GF-02, Nov. 2017
SSVs of GdN(27nm)/NbN(3.5nm)/GdN(13nm) trilayers were formed with the reactive sputtering technique in a UHV system. The Gd monolayers were inserted between NbN/GdN interfaces to compensate the nitrogen less interfaces. SSE signals were clearly observed from 2.5 K down to 1.1 K. The anti-parallel (AP) state showed a TC of 1.7 K while in the parallel (P) state it was 1.4 K. An equivalent induced magnetic field was quantitatively estimated by the Kulic-Endres modelf. A pair breaking factor in the model which was evaluated from a ration ofTC in the P and AP states was enhanced by hundredfold by tailoring interfaces by the Gd insertion layers. In our presentation, we will discuss a relationship between pair breaking factors and interfacial magnetic moments analyzed by PNR.
This work was supported by NSF and ONR grants, JSPS, and Fundacion Seneca (19791/PD/15). The research conducted at the SNS is sponsored by the Scientific User Facilities Division, Office of BES, U.S. DOE.
References
1P.G. De Gennes, Phys. Lett. 23, 10 (1966).
2B. Li, N. Roschewsky, B.A. Assaf, M. Eich, M. Epstein-Martin, D. Heiman, M. Muzenberg, and J.S. Moodera, Phys. Rev. Lett. 110, 97001 (2013).
3Y. Zhu, A. Pal, M.G. Blamire, and Z.H. Barber, Nat. Mater. 16, 195 (2017).
4Y. Takamura et al., MMM conf., Pittsburgh, USA, GF-02, Nov. 2017