Low-drive, temperature stable ferrite for laminated memory arrays

Research on thermally stable ferrite materials tailored to laminated memory arrays operated at low current levels is described. For this application a ferrite combining low coercive force, fast switching, good squareness, small grain size, high Curie temperature, and high resistivity is necessary. The manganese-ferrous ferrite, manganese-lithium ferrite, and manganese-magnesium-ferrite systems (including, in some cases, small amounts of other metal ions) are studied. A manganese-magnesium-zinc ferrite (Zn 0.11 Mn 0.41 Mg 0.83 Fe 16.3 O 4 ) has the best combination of properties for laminated memory arrays. Arrays containing 256 × 100 conductors were successfully operated, without thermal or current compensation, over a temperature range of 0° to 50°C. The memory arrays described have operating characteristics that are compatible with integrated semiconductor drive currents.