a substrate having an arrangement of self - assembling magnetic domains and a method of fabrication therefor . in some embodiments , a substrate is patterned with a plurality of chemically contrasted alignment features , and a block copolymer having a magnetic component and a non - magnetic component is deposited onto the substrate . the block copolymer self - assembles into a sequence of magnetic domains responsive to the alignment features . the period of the alignment features is between about 2 times and about 10 times the period of the magnetic domains .