Explain the operation of a magnetic tunnel junction (MTJ) in magnetoresistive random-access memory (MRAM).
1 Answer
Magnetoresistive Random-Access Memory (MRAM) is a type of non-volatile memory that uses magnetic tunnel junctions (MTJs) as its fundamental storage elements. MTJs are devices that exploit the phenomenon of magnetoresistance to store and read data. Let's break down the operation of a magnetic tunnel junction in MRAM:
Basic Structure:
A magnetic tunnel junction (MTJ) consists of two ferromagnetic layers separated by a thin insulating barrier. One of the ferromagnetic layers is referred to as the "fixed layer," and its magnetic orientation remains constant. The other ferromagnetic layer is known as the "free layer," and its magnetic orientation can be altered.
Tunneling Magnetoresistance (TMR):
The key principle that enables the operation of an MTJ is the phenomenon called "tunneling magnetoresistance" (TMR). TMR is a quantum mechanical effect that occurs when electrons pass through the insulating barrier between the two ferromagnetic layers. The probability of electron tunneling depends on the relative orientation of the magnetic moments in the two layers.
Parallel and Anti-parallel Configurations:
When the magnetization directions of the fixed and free layers are parallel, the TMR effect is enhanced, leading to a lower resistance for the MTJ. Conversely, when the magnetization directions are anti-parallel, the TMR effect is reduced, resulting in a higher resistance for the MTJ.
Writing Operation:
To write data into an MTJ, a current is applied through the MTJ. This current exerts a torque on the magnetic moment of the free layer, causing it to switch its orientation to either align parallel or anti-parallel with the fixed layer, depending on the desired data state.
Reading Operation:
During the read operation, a small voltage is applied across the MTJ. The resistance of the MTJ depends on the relative orientation of the magnetic moments in the fixed and free layers. By sensing the resistance, the state of the MTJ (and thus the stored data) can be determined. A low resistance indicates a parallel configuration (corresponding to one data state), while a high resistance indicates an anti-parallel configuration (corresponding to the other data state).
Non-Volatile Memory:
MRAM is non-volatile because the data stored in the MTJs remains even when the power supply is disconnected. This is because the magnetic orientation of the free layer is retained, making it a stable storage element.
In summary, the magnetic tunnel junction (MTJ) in Magnetoresistive Random-Access Memory (MRAM) operates based on the tunneling magnetoresistance (TMR) effect, where the relative orientation of the magnetic moments in the fixed and free layers determines the resistance. By applying currents to write data and sensing resistance to read data, MRAM provides a non-volatile and fast memory technology.
Basic Structure:
A magnetic tunnel junction (MTJ) consists of two ferromagnetic layers separated by a thin insulating barrier. One of the ferromagnetic layers is referred to as the "fixed layer," and its magnetic orientation remains constant. The other ferromagnetic layer is known as the "free layer," and its magnetic orientation can be altered.
Tunneling Magnetoresistance (TMR):
The key principle that enables the operation of an MTJ is the phenomenon called "tunneling magnetoresistance" (TMR). TMR is a quantum mechanical effect that occurs when electrons pass through the insulating barrier between the two ferromagnetic layers. The probability of electron tunneling depends on the relative orientation of the magnetic moments in the two layers.
Parallel and Anti-parallel Configurations:
When the magnetization directions of the fixed and free layers are parallel, the TMR effect is enhanced, leading to a lower resistance for the MTJ. Conversely, when the magnetization directions are anti-parallel, the TMR effect is reduced, resulting in a higher resistance for the MTJ.
Writing Operation:
To write data into an MTJ, a current is applied through the MTJ. This current exerts a torque on the magnetic moment of the free layer, causing it to switch its orientation to either align parallel or anti-parallel with the fixed layer, depending on the desired data state.
Reading Operation:
During the read operation, a small voltage is applied across the MTJ. The resistance of the MTJ depends on the relative orientation of the magnetic moments in the fixed and free layers. By sensing the resistance, the state of the MTJ (and thus the stored data) can be determined. A low resistance indicates a parallel configuration (corresponding to one data state), while a high resistance indicates an anti-parallel configuration (corresponding to the other data state).
Non-Volatile Memory:
MRAM is non-volatile because the data stored in the MTJs remains even when the power supply is disconnected. This is because the magnetic orientation of the free layer is retained, making it a stable storage element.
In summary, the magnetic tunnel junction (MTJ) in Magnetoresistive Random-Access Memory (MRAM) operates based on the tunneling magnetoresistance (TMR) effect, where the relative orientation of the magnetic moments in the fixed and free layers determines the resistance. By applying currents to write data and sensing resistance to read data, MRAM provides a non-volatile and fast memory technology.