2.9 Hyperfine Interaction
57
Case I: In case of isotopes of majority of the inorganic semiconductors, nuclear
spins are non-zero. For instance, all natural isotopes of Ga, In, Al, Sb and As have
finite nuclear spins accompanied by substantial magnetic moments. Hence, hyperfine
interaction is supposed to be particularly significant in technologically relevant III–V
semiconductors, e.g., (Al)GaAs, In(Al)As etc.
Case II: Cd, Zn, S, Se and Te have isotopes, carrying nuclear spins, with less
natural abundance.
– Hyperfine interaction in II–VI semiconductors is weaker compared to their III–V
counterparts.
– Hyperfine interaction has been observed to be weak in case of elemental
semiconductors, such as Si and Ge.
Case III: For organic semiconductors, two main constituent elements are carbon
and hydrogen. In case of carbon atoms, the most abundant (98.89%) isotope 12C
possesses zero nuclear spin. Thus, it is not supposed to contribute to the hyperfine
interaction. The major contributions to hyperfine interaction in organics originate
from the hydrogen atoms (1H, abundance > 99.98%). Negligible contributions to
hyperfine interaction arise from 13C (natural abundance 1.109%) and other minor
constituent elements.
2.10 Spin Valve
Spin valve is the basic building block of spintronics (Jedema et al. 2002; Pramanik
et al. 2006). It is at the core of constructing diversified spintronics-based data storage
devices, such as GMR read head sensors of computer hard disk drives, magnetic
random access memory (MRAM) devices, spin-transfer torque-based devices, spinpolarized light emitting diodes etc. Furthermore, spin valve is also widely used to
study and measure properties associated with spin transport in paramagnetic metals
or semiconductors, like spin diffusion length, L s and then spin relaxation time τ s
related by the equation
L S =
D S τ S
(2.54)
where D S = spin diffusion coefficient. Therefore, spin valve is an important measurement device as well. Thus, we may consider spin valve as an extremely important
device, both from the viewpoint of spin-physics and spintronics or optospintronics
device applications.
57
Case I: In case of isotopes of majority of the inorganic semiconductors, nuclear
spins are non-zero. For instance, all natural isotopes of Ga, In, Al, Sb and As have
finite nuclear spins accompanied by substantial magnetic moments. Hence, hyperfine
interaction is supposed to be particularly significant in technologically relevant III–V
semiconductors, e.g., (Al)GaAs, In(Al)As etc.
Case II: Cd, Zn, S, Se and Te have isotopes, carrying nuclear spins, with less
natural abundance.
– Hyperfine interaction in II–VI semiconductors is weaker compared to their III–V
counterparts.
– Hyperfine interaction has been observed to be weak in case of elemental
semiconductors, such as Si and Ge.
Case III: For organic semiconductors, two main constituent elements are carbon
and hydrogen. In case of carbon atoms, the most abundant (98.89%) isotope 12C
possesses zero nuclear spin. Thus, it is not supposed to contribute to the hyperfine
interaction. The major contributions to hyperfine interaction in organics originate
from the hydrogen atoms (1H, abundance > 99.98%). Negligible contributions to
hyperfine interaction arise from 13C (natural abundance 1.109%) and other minor
constituent elements.
2.10 Spin Valve
Spin valve is the basic building block of spintronics (Jedema et al. 2002; Pramanik
et al. 2006). It is at the core of constructing diversified spintronics-based data storage
devices, such as GMR read head sensors of computer hard disk drives, magnetic
random access memory (MRAM) devices, spin-transfer torque-based devices, spinpolarized light emitting diodes etc. Furthermore, spin valve is also widely used to
study and measure properties associated with spin transport in paramagnetic metals
or semiconductors, like spin diffusion length, L s and then spin relaxation time τ s
related by the equation
L S =
D S τ S
(2.54)
where D S = spin diffusion coefficient. Therefore, spin valve is an important measurement device as well. Thus, we may consider spin valve as an extremely important
device, both from the viewpoint of spin-physics and spintronics or optospintronics
device applications.