10.6 Spintronics Sensors
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the corresponding resistance of the sensor fluctuates continuously. The fluctuation of resistance of this TMR sensor is in accordance with the rotation of the top
magnet and in this way, the TMR sensor can be employed as an angle sensor.
• In this context, we should mention that in comparison to GMR-based sensors,
MTJ sensors offer a higher MR ratio and sensitivity. However, the top electrodes
of MTJ sensors are generally thicker than GMR sensors. This, in turn, makes
the sensing field of the free ferromagnetic layer smaller and thereby limiting its
application. Another challenge lies on the high intrinsic noise of MTJ sensors for
achieving ultra-high sensitivities.
TMR-Based Biosensors
MTJ-based sensors have also found their application as Biosensors. The MgO-based
MTJ sensor is bio-functionalized with Alpha Fetoprotein (AFP) capture antibodies
where Metabolic Nutrition Programs (MNPs) are functionalized with AFP detection
antibodies. A sandwich-assay configuration is generally adopted for the detection of
AFP. A complete binding of target AFP to capture antibodies is achieved. Finally,
the excess MNPs are eliminated by cleansing the Phosphate Buffered Saline (PBST)
solution.
TMR-Based Sensors for Genotyping
A proof-of-concept detection of DNA, employing MTJ-based sensors was exhibited
in 2005. In that case, MTJs with Al 2 O 3 barrier layer were utilized to detect singlestranded DNA attached with MnFe 2 O 4 nanoparticles. However, the first quantitative
detection of DNA was accomplished in MgO-based MTJ sensors.
10.7 Spin FET
Spin-based logic is presently being investigated as one of the beyond-CMOS
computing technologies to supplement complementary metal oxide semiconductor
(CMOS) field effect transistors (FET) in microprocessors. Strong-willed research
in spintronic has resulted in commercialization of MRAM and STRAM and had an
immense influence on day-to-day life. Now the question comes up whether the spintronic devices are competent enough for similar success in logic. One of the strong
contenders may be the spin field-effect transistor (spin FET), which is basically a
three-terminal device that utilizes ferromagnetic contacts in the source and drain as
spin injector and detector.
Spin FET, visualized by Datta and Das in 1990, opens a gateway to spin information processing (Datta 2018; Datta and Das 1990). Although the researches on
semiconductor spintronics have made coherent manipulation of electron spins in
semiconductors feasible yet the realization of a functional spin field-effect transistor
for information processing has not been achieved. The numbers of primary challenges are low spin-injection efficiency due to resistance mismatch, spin relaxation,
253
the corresponding resistance of the sensor fluctuates continuously. The fluctuation of resistance of this TMR sensor is in accordance with the rotation of the top
magnet and in this way, the TMR sensor can be employed as an angle sensor.
• In this context, we should mention that in comparison to GMR-based sensors,
MTJ sensors offer a higher MR ratio and sensitivity. However, the top electrodes
of MTJ sensors are generally thicker than GMR sensors. This, in turn, makes
the sensing field of the free ferromagnetic layer smaller and thereby limiting its
application. Another challenge lies on the high intrinsic noise of MTJ sensors for
achieving ultra-high sensitivities.
TMR-Based Biosensors
MTJ-based sensors have also found their application as Biosensors. The MgO-based
MTJ sensor is bio-functionalized with Alpha Fetoprotein (AFP) capture antibodies
where Metabolic Nutrition Programs (MNPs) are functionalized with AFP detection
antibodies. A sandwich-assay configuration is generally adopted for the detection of
AFP. A complete binding of target AFP to capture antibodies is achieved. Finally,
the excess MNPs are eliminated by cleansing the Phosphate Buffered Saline (PBST)
solution.
TMR-Based Sensors for Genotyping
A proof-of-concept detection of DNA, employing MTJ-based sensors was exhibited
in 2005. In that case, MTJs with Al 2 O 3 barrier layer were utilized to detect singlestranded DNA attached with MnFe 2 O 4 nanoparticles. However, the first quantitative
detection of DNA was accomplished in MgO-based MTJ sensors.
10.7 Spin FET
Spin-based logic is presently being investigated as one of the beyond-CMOS
computing technologies to supplement complementary metal oxide semiconductor
(CMOS) field effect transistors (FET) in microprocessors. Strong-willed research
in spintronic has resulted in commercialization of MRAM and STRAM and had an
immense influence on day-to-day life. Now the question comes up whether the spintronic devices are competent enough for similar success in logic. One of the strong
contenders may be the spin field-effect transistor (spin FET), which is basically a
three-terminal device that utilizes ferromagnetic contacts in the source and drain as
spin injector and detector.
Spin FET, visualized by Datta and Das in 1990, opens a gateway to spin information processing (Datta 2018; Datta and Das 1990). Although the researches on
semiconductor spintronics have made coherent manipulation of electron spins in
semiconductors feasible yet the realization of a functional spin field-effect transistor
for information processing has not been achieved. The numbers of primary challenges are low spin-injection efficiency due to resistance mismatch, spin relaxation,