Coexistence of glassy antiferromagnetism and giant magnetoresistance in Fe/Cr multilayer structures

Abstract

Using temperature-dependent magnetoresistance and magnetization measurements on Fe/Cr multilayers that exhibit pronounced giant magnetoresistance (GMR), we have found evidence for the presence of a glassy antiferromagnetic phase. This phase reflects the influence of interlayer exchange coupling (IEC) at low temperature ( T<140 K ) and is characterized by a field-independent glassy transition temperature, T g, together with irreversible behavior having logarithmic time dependence below a “de Almeida and Thouless” critical field line. At room temperature, where the GMR effect is still robust, IEC plays only a minor role, and it is the random potential variations acting on the magnetic domains that are responsible for the antiparallel interlayer domain alignment.