A spin-transfer torque memory apparatus and 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, the magnetic tunnel junction data cell having a first resistance
state and storing the first bit line read voltage in a first voltage
storage device. Then applying a low resistance state polarized write
current through the magnetic tunnel junction data cell, forming a low
second resistance state magnetic tunnel junction data cell. A second read
current is applied through the low second resistance state magnetic
tunnel junction data cell to forming a second bit line read voltage. The
second bit line read voltage is stored in a second voltage storage
device. The method also includes comparing the first bit line read
voltage with the 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.