MEMORY CORES HAVING RECTANGULAR HYSTERESIS LOOP CHARACTERISTICS AND METHOD OF MANUFACTURING THE SAME

摘要

1299667 Ferrite cores HITACHI Ltd 29 April 1970 [6 May 1969 (2)] 20645/70 Heading H1H A magnetic memory core having a rectangular hysteresis characteristic is made of a composition including Li, FeSP3+/SPZnSP2+/SP, O together with MnSP3+/SP and/or MnSP2+/SP and represented by the formula where 0À03 # x + y # 0À75; 0À09 # z # 0À42. SP4/SP The composition may also contain V 2 O 5 and/or SiO 2 in amounts not greater than 2À0 wt. per cent and 3À0 wt. per cent respectively. The core is made by pre-firing a mixture of oxideforming metal compounds, e.g. oxalates or carbonates, grinding, pressing into shape and sintering. Sintering may be effected at 1000-1200‹ C. for, e.g. 2-20 minutes in an oxygen atmosphere when MnSP2+/SP is absent, in conditions of reducing O 2 partial pressure with increase in MnSP2+/SP/MnSP3+/SP ratio, and in a reducing atmosphere when MnSP3+/SP is absent. In examples, wet or dry mixtures of oxide precursors are fired at 700- 900‹ C. for 2 hrs., ground, mixed into granules with P.V.A., press-moulded into toroids and sintered on O 2 , air or N 2 . The toroids have a rectangular hysteresis loop.