APPLICATION OF ORTHOFERRITES TO DOMAIN-WALL DEVICES

Orthoferrites are of general formula RFe03 where R is any rare earth or yttrium. They are usually flux grown as large single crystals and then processed to provide platelets several mils in thickness. A high uniaxial anisotropy gives rise to a single unique easy magnetization direction parallel to the c axis above room temperature in all orthoferrites except SmFeO3. A low saturation magnetization results from the canting of a pair of antiparallel spin systems. Platelets prepared so that the easy axis of magnetization is normal to the planar surface display a serpentine domain pattern made visible by the Faraday effect. Under Under specific conditions cylindrical domains are observed. These domains, which in Sm0.55Tb0.45Fe03 are as small as 0.8 mil in diameter, can be manipulated to perform memory and logic. Three techniques can be used to propagate cylindrical domains. The first uses a sequence of current pulses applied to a conductor array. The second requires an in-plane rotating field acting on a structured Perrnalloy pattern to generate traveling positive and negative poles. These poles selectively attract and repel a cylindrical domain and thereby control its motion. The movement of an inchworm most closely approximates the propagation mechanism of the third technique. Interacting a pulsating domain with a wedgelike Perma11oy pattern results in a unidirectional movement. © 1969, IEEE. All rights reserved.