MICROMAGNETIC BEHAVIOR AND RECORDING PERFORMANCE IN HIGH-DENSITY 5 GBIN(2) COCRPTTA MEDIUM/

Micromagnetic studies of the magnetization process in high density 5 G b/in.(2) CoCrPtTa and 0.8 Gb/in.(2) CoCrTa media were carried out in c onjunction with recording performance measurements. The maximum value of the delta M curves measured at room temperature and at 373 K is sma ller for CoCrPtTa compared to CoCrTa which indicates lesser intergranu lar exchange coupling in the quaternary medium. At room temperature, t he Barkhausen volume V, which is the smallest switching unit in magne tization reversal, corresponds approximately to one grain for CoCrPtTa but to three to four grains for CoCrTa. These results are consistent with the lower media noise found for CoCrPtTa especially at high bit d ensities. A decrease in V to the size of one grain for CoCrTa is obse rved for temperatures below 200 K. The reduced intergranular exchange is confirmed by delta M measurements at 77 K. Low coupling, however, l eads to low values of M-r which leads to a reduction in the reading si gnal. The value of M-r. for CoCrTa at 77 K is 60% greater than that of CoCrPtTa at room temperature despite the reduced exchange coupling in dicating that larger values of M-r can still be achieved while confini ng the switching volume to no more than a grain. (C) 1997 American Ins titute of Physics.