A transmission electron energy loss spectrometry study for the source of an anomalous positive exchange bias in a Ni{sub}80Fe{sub}20/Ni{sub}xFe{sub}(1-x)O thin-film bilayer

摘要

Exchange coupling between a ferromagnetic and antiferromagnetic bilayer that results in an exchange bias shift of the hysteresis loop in the positive field direction (i.e. positive exchange bias) was first reported in the pure ferromagnet/antiferromagnet thin-film systems of Fe/FeF{sub}2 and Fe/MnF{sub}2 [1]. In these materials a large cooling field was required to reverse the easy direction of the exchange coupling and provided the mechanism for positive exchange bias [2]. Using transmission electron energy loss spectrometry we explore the possible origins for an atypical temperature dependent positive exchange bias in a Ni{sub}80Fe{sub}20/Ni{sub}xFe{sub}(1-x)O thin-film when it is zero-field cooled that shows the usual negative exchange bias when it is field cooled.