The optimization of head field gradient and inter-granular exchange coupling was studied usinmicromagnetics simulation so that we could predict future R/W properties with combinations of different head and medium properties in perpendicular magnetic recording. The results revealed that SNR degradation with media exchange coupling could be suppressed by using a shielded head with a high field gradient. Shielded heads are also effective when the average size of media grains is reduced to 75% to achieve SNR improvements of 2-3 dB.