1. A memory unit comprising: a giant magnetoresistance cell electrically coupled between a write bit line and a write source line, a write current passing through the giant magnetoresistance cell switches the giant magnetoresistance cell between a high resistance state and a low resistance state; and a magnetic tunnel junction data cell electrically coupled between a read bit line and a read source line, the magnetic tunnel junction data cell is configured to switch between a high resistance state and a low resistance state by magnetostatic coupling with the giant magnetoresistance cell, and be read by a read current passing though the magnetic tunnel junction data cell; wherein the read source line and the write source line is a common source line and the read bit line is separately addressable from the write bit line and a write transistor is electrically coupled between the source line and the giant magnetoresistance cell, and a read transistor is electrically coupled between the source line and the magnetic tunnel junction data cell.