A random access memory cell is described which is capable of storing
multiple information states in a single physical bit. The basic structure
combines a conventional MTJ with a reference stack that is
magnetostatically coupled to the MTJ. The MTJ is read in the usual way
but data is written and stored in the reference stack. Through use of two
bit lines, the direction of magnetization of the free layer can be
changed in small increments each unique direction representing a
different information state.