Effect of post annealing on spin accumulation and transport signals in Co2FeSi/MgO/n+-Si on insulator devices

Ajay Tiwari,Hideyuki Sugiyama,Mizue Ishikawa,Yoshiaki Saito,Tomoaki Inokuchi,Nobuki Tezuka

doi:10.1063/1.4960210

Abstract

The post annealing temperature dependence of spin accumulation and transport signals in Co2FeSi/MgO/n+-Si on insulator were investigated. The spin signals were detected using 3- and 4-terminal Hanle, 2-terminal local and 4-terminal nonlocal magnetoresistance measurements. The post annealing temperature (TA) dependence of the magnitude in 3-terminal narrow Hanle signals is nearly constant up to TA &lt; 400°C, however a slight decrease above TA ≥ 400°C is observed. This behavior is consistent with the TA dependence of the magnitude of 4-terminal nonlocal magnetoresistance (MR) signals. The spin polarization estimated from the 3-terminal narrow Hanle signals and the magnitude of 2-terminal local MR signals show a slight improvement with increasing post annealing temperature with a peak at around 325°C and then start reducing slowly. The slight increase in the spin signal would be due to high spin polarization of Co2FeSi as a result of structural ordering. The 2-terminal local MR signals do not vary significantly by annealing between as-deposited and TA = 400°C, indicating the robustness of our device. This result would be useful for future Si spintronics devices.

Highlights

Many studies on silicon (Si) spintronics for realizing the spin-MOSFETs have been reported because of the observation of room-temperature spin signals in Si.[1,2,3,4,5,6,7] In order to realize the Spin-MOSFET, highly efficient spin injection and detection in ferromagnet/semiconductor (FM/SC) are required
The 2-terminal local MR signals do not vary significantly by annealing between as-deposited and TA = 400◦C, indicating the robustness of our device. This result would be useful for future Si spintronics devices
TA dependence on spin accumulation and transport signals for Co2FeSi/MgO (1.3 nm)/Mg (0.6 nm)/n+-Si on insulator (SOI) have been discussed As a result, we find that the behavior in the 3-terminal narrow Hanle signals is nearly consistent with the 4-terminal nonlocal

Summary

Introduction

Many studies on silicon (Si) spintronics for realizing the spin-MOSFETs have been reported because of the observation of room-temperature spin signals in Si.[1,2,3,4,5,6,7] In order to realize the Spin-MOSFET, highly efficient spin injection and detection in ferromagnet/semiconductor (FM/SC) are required. Heusler alloys are attractive spin polarized sources for spin injectors/detectors because many of them have been predicted to be half-metallic (spin polarization of 1) The Co-based Heusler alloys (Co2YZ, where Y is usually a transition metal and Z is a main group element) have attracted much interest as highly spin-polarized materials.[12,13,14] This is because of the half-metallic nature (theoretically predicted for many of these alloys) and because of their high Curie temperatures, which are well above room temperature (RT).[15,16,17,18] The Co2YZ thin films have been widely applied to magnetic tunnel junctions (MTJs), in particular, in combination with a MgO barrier.[12,13,19,20,21]

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Results

Conclusion