Microwave assisted magnetic recording(MAMR) is one of the candidates for realizing ultrahigh density recording over Tbits/inch^2.In this study, signal-to-noise ratio (SNR) and recorded track width have been investigated for achieving high track density in MAMR. Moderate intergrain exchange interaction is know to improve SNR by suppressing the generation of islands reversals in recorded bits. On the other hand, intergrain exchange interaction was found to widen recording track width, which tends to decrease track density. However, track density as high as 1129 ktpi was estimated to be realizable in MAMR on the assumption of no intergrain exchange interaction in this study.