Creation and annihilation of 360° domain walls in magnetic tunnel junctions with exchange-biased artificial ferrimagnet

Abstract

In state-of-the-art read heads, exchange-biased artificial ferrimagnet hard layers are extensively used. In this paper, we analyze different magnetic tunnel junction stacks with respect to the formation and annihilation of 360° walls in their hard subsystem, visualized using magnetic force microscopy. The existence of 360° walls in a magnetic tunnel junction has a microscopic origin, i.e., the local competition between different coupling mechanisms in the layered system, and can qualitatively be interpreted from a strong but reversible reduction in minor loop tunnel magnetoresistance. Therefore, the magnetic history of a tunnel junction is of great importance in the interpretation of minor loop measurements.