Crystallographic Damage to Mn-Ir Antiferromagnets by Ion Beam Etching

The etching damage caused by ion beam etching with a low energy from 100 to 425 eV to manganese (Mn) - iridium (Ir) antiferromagnets was investigated by fluorescent x-ray analysis and a way of precise grazing incidence-controlled x-ray diffraction. Two kinds of damage were observed: one was an increase in iridium content, which increased as the etching depth (detched) increased. The other kind of damage was a lattice strain. IBE at a higher acceleration voltage (Vacc) and larger detched caused expansion of the in-plane MnIr(220) spacing near the etched surface; the out-of-plane MnIr(202) spacing remained constant. A smaller detched limited the lattice strain. The depth at which the lattice strain occurred was about 12 nm from the surfaces etched with various Vacc's and to various detched's. The causes of these two types of damage might be the same, i.e., preferential etching of Mn atoms at the surface.