For a start, the grains of magnetite are not strong enough magnets to make a useful memory, and the size of each domain (20 microns across) is huge by modern computing standards.

首先对于可用的存储器来说，那些磁铁颗粒的磁性还不够强大，并且每个区域的尺寸（20微米的跨度）对现在计算机标准来说太大了。