180
7 Opto-spintronics
Fig. 7.12 Ultrafast modification of magnetic order in FeRh (a–d) (adapted and redrawn from Ref.
(Nˇ emec et al. 2018))
7.10 All-Optical Spintronic Switching
The prevailing notable magnetization switching technologies (see Fig. 7.13) are based
on spin transfer torque (STT), spin–orbit torque (SOT) and magnetoelectric/voltagecontrolled (ME) switching. Speed is the major hurdle towards the extensive selection
of spintronic devices. The switching time of spintronic devices is still on the order of
hundreds of picoseconds, which is much greater than that of the silicon field-effect
transistors where it less than 5 ps.We have already observed that ultrafast femtosecond
laser can control and demagnetize the magnetic medium on sub-picosecond time
scales even in the absence of external magnetic field. Now the question is whether
we can switch the magnetization without magnetic field? The answer is yes, we can.
Femtosecond laser pulse can also switch the magnetization, i.e., can reverse the spins
from one direction to other without magnetic field. This effect is known as all optical
spin switching (AOS). It bears tremendous potential in the field of magnetic data
storage, memory and logic based devices.
AOS combines two important characteristics, i.e., (i) strong storage capability of
spintronic media and (ii) efficient speed delivery power of fs laser, yet free from
magnetic field. All optical switching can broadly be classified into two categories.
One category is based on helicity of polarized light and another one is based on
7 Opto-spintronics
Fig. 7.12 Ultrafast modification of magnetic order in FeRh (a–d) (adapted and redrawn from Ref.
(Nˇ emec et al. 2018))
7.10 All-Optical Spintronic Switching
The prevailing notable magnetization switching technologies (see Fig. 7.13) are based
on spin transfer torque (STT), spin–orbit torque (SOT) and magnetoelectric/voltagecontrolled (ME) switching. Speed is the major hurdle towards the extensive selection
of spintronic devices. The switching time of spintronic devices is still on the order of
hundreds of picoseconds, which is much greater than that of the silicon field-effect
transistors where it less than 5 ps.We have already observed that ultrafast femtosecond
laser can control and demagnetize the magnetic medium on sub-picosecond time
scales even in the absence of external magnetic field. Now the question is whether
we can switch the magnetization without magnetic field? The answer is yes, we can.
Femtosecond laser pulse can also switch the magnetization, i.e., can reverse the spins
from one direction to other without magnetic field. This effect is known as all optical
spin switching (AOS). It bears tremendous potential in the field of magnetic data
storage, memory and logic based devices.
AOS combines two important characteristics, i.e., (i) strong storage capability of
spintronic media and (ii) efficient speed delivery power of fs laser, yet free from
magnetic field. All optical switching can broadly be classified into two categories.
One category is based on helicity of polarized light and another one is based on