Imprinting artificial magnetic structures (invited)

Recently we created La/Fe multilayers with a helical magnetic structure imp rinted from the conditions of growth rather than by the magnetic interactio ns between layers. Each sublayer was 30 Angstrom thick, and during depositi on the sample was rotated in an external field of 3 Oe, a field strong enou gh to magnetize the Fe layer being deposited but not sufficient to perturb the magnetization of the Fe layers already grown. As a result adjacent Fe l ayers formed a helical structure with a chirality and periodicity determine d by the rotational direction and speed of the substrate and the rate of de position. Following this discovery an extensive set of experiments (mainly using Kerr effect magnetometry and polarized neutron reflectivity) was unde rtaken to ascertain the stability of imprinted magnetic structures, and to understand the onset of magnetization during growth. La/Fe imprinted helica l magnetic structures (of different La and Fe thicknesses) were found to be stable in time and to be permanently erased only by magnetic fields larger than 90 Oe. (C) 1999 American Institute of Physics. [S0021-8979(99)67408-4 ].