A word-organized NDRO memory using fluted magnetic films

Fluted films are thin permalloy films consisting of narrow parallel strips ( wide) of alternating thickness (typically Å, Å). These strips, parallel to the easy direction ( axis), introduce a microshape anisotropy which stabilizes hard direction locked states. The two hard direction states with either positive or negative component of magnetization are used to characterize binary one or zero, respectively. In a word-organized memory, the extraordinary stability of these locked states can be used for a nondestructive readout. For write-in, overlapping of a word field with an advanced (one) or a delayed (zero) bit field of equal polarity is required. Word field or bit field alone leaves the locked states unchanged. Thus, in selected elements along a word line write-in is possible. Readout and write-in occur by the inherently fast magnetization rotation. The attainable speed of a readout is essentially a question of compensation of capacitive and inductive noise in the sense line. By use of dummy lines and fast differential sense amplifiers, sufficient noise cancellation appears possible to allow readout repetition rates of 50 Mc/s or above.