2.13 Spin Current Measurement Mechanism
69
paramagnetic metal. In the paramagnetic metal, this spin current (J s ) is converted
into an electric field E ISHE due to the inverse spin Hall effect (ISHE) and is given by
E ISHE = [(θ SH ρ) × (2e )J s × σ ]/A,
(2.56)
where θ SH , ρ and A are the spin Hall angle of PM, the electric resistivity of PM and
the contact area between F and PM, respectively. By measuring E ISHE in the PM film,
the longitudinal SSE can be detected electrically.
2.14 Conclusions
In this chapter, we discussed some important notions, such as spin polarization, spin
filter effect, spin injection, spin accumulation, spin relaxation, spin extraction etc.
We have also discussed passive spintronic devices, such as spin valves in this chapter.
Currently available commercial spintronic products, such as magnetic read heads for
reading data in computer hard disks or entertainment systems such as Apple iPods,
and magnetic random access memory utilize these passive devices. Hence, sufficient
knowledge is essential for engineers to understand these devices. In this chapter, we
have also presented different kinds of spin relaxation, in both time and space, of
conduction electrons in metals and semiconductors. In this direction, four primary
spin relaxation mechanisms such as the D’yakonov-Perel’, the Elliott–Yafet, the BirAronov-Pikus and hyperfine interactions with nuclear spins have been discussed.
Since spin relaxation mechanism poses limitations to the performance of most of the
spintronics devices, it is an important issue for thorough discussion. Ultimately, the
objective of all device engineers and physicists is to minimize the spin relaxation
rate in spintronics devices so that they become more robust and useful. We have
also discussed field and heat-driven spintronics effect, i.e., spin Hall effect, Seebeck
effect and spin current measurement mechanism. These effects are important in the
context of terahertz spintronics devices and have been discussed in Chap. 8. Our
objective is to introdduce important concepts about spintronics to the reader to make
them well conversant with the topic.
2.15 Exercises
1. Define spin polarization.
2. What is spin filter effect in a ferromagnet? State the physical interpretation of
spin asymmetry ‘A’.
3. Define spin detection efficiency.
4. Why in case of ferromagnet the electronic transport is spin-dependent? Hence
define spin filter effect in ferromagnet.
5. Define spin injection process.
69
paramagnetic metal. In the paramagnetic metal, this spin current (J s ) is converted
into an electric field E ISHE due to the inverse spin Hall effect (ISHE) and is given by
E ISHE = [(θ SH ρ) × (2e )J s × σ ]/A,
(2.56)
where θ SH , ρ and A are the spin Hall angle of PM, the electric resistivity of PM and
the contact area between F and PM, respectively. By measuring E ISHE in the PM film,
the longitudinal SSE can be detected electrically.
2.14 Conclusions
In this chapter, we discussed some important notions, such as spin polarization, spin
filter effect, spin injection, spin accumulation, spin relaxation, spin extraction etc.
We have also discussed passive spintronic devices, such as spin valves in this chapter.
Currently available commercial spintronic products, such as magnetic read heads for
reading data in computer hard disks or entertainment systems such as Apple iPods,
and magnetic random access memory utilize these passive devices. Hence, sufficient
knowledge is essential for engineers to understand these devices. In this chapter, we
have also presented different kinds of spin relaxation, in both time and space, of
conduction electrons in metals and semiconductors. In this direction, four primary
spin relaxation mechanisms such as the D’yakonov-Perel’, the Elliott–Yafet, the BirAronov-Pikus and hyperfine interactions with nuclear spins have been discussed.
Since spin relaxation mechanism poses limitations to the performance of most of the
spintronics devices, it is an important issue for thorough discussion. Ultimately, the
objective of all device engineers and physicists is to minimize the spin relaxation
rate in spintronics devices so that they become more robust and useful. We have
also discussed field and heat-driven spintronics effect, i.e., spin Hall effect, Seebeck
effect and spin current measurement mechanism. These effects are important in the
context of terahertz spintronics devices and have been discussed in Chap. 8. Our
objective is to introdduce important concepts about spintronics to the reader to make
them well conversant with the topic.
2.15 Exercises
1. Define spin polarization.
2. What is spin filter effect in a ferromagnet? State the physical interpretation of
spin asymmetry ‘A’.
3. Define spin detection efficiency.
4. Why in case of ferromagnet the electronic transport is spin-dependent? Hence
define spin filter effect in ferromagnet.
5. Define spin injection process.