A spin-transfer torque memory apparatus and non-destructive self-reference
read schemes are described. One method of self-reference reading a
spin-transfer torque memory unit includes applying a first read current
through a magnetic tunnel junction data cell and forming a first bit line
read voltage and storing the first bit line read voltage in a first
voltage storage device. The magnetic tunnel junction data cell has a
first resistance state. Then the method includes applying a second read
current thorough the magnetic tunnel junction data cell having the first
resistance state and forming a second bit line read voltage and storing
the second bit line read voltage in a second voltage storage device. The
first read current is less than the second read current. Then the stored
first bit line read voltage is compared with the stored second bit line
read voltage to determine whether the first resistance state of the
magnetic tunnel junction data cell was a high resistance state or low
resistance state.