Cooperative Multiscale Aging in a Ferromagnet/Antiferromagnet Bilayer

Abstract

We utilize anisotropic magnetoresistance to study temporal evolution of the magnetization state in epitaxial Ni${}_{80}$Fe${}_{20}$/Fe${}_{50}$Mn${}_{50}$ ferromagnet/antiferromagnet bilayers. The resistance exhibits power-law evolution over a wide range of temperatures and magnetic fields, indicating that aging is characterized by a wide range of activation time scales. We show that aging is a cooperative process, i.e. the magnetic system is not a superposition of weakly interacting subsystems characterized by simple Arrhenius activation. The observed effects are reminiscent of avalanches in granular materials, providing a conceptual link to a broad class of critical phenomena in other complex condensed matter systems.

5 pages, 5 figures

References in corpus (3)

• Random Fields, Topology, and The Imry-Ma Argument
• Spin configuration in a frustrated ferromagnetic/antiferromagnetic thin film system
• Role of interface coupling inhomogeneity in domain evolution in exchange bias

Cited by in corpus (5)

• Spin glass transition in a thin-film NiO/Permalloy bilayer
• Experimental demonstration and analysis of random field effects in ferromagnet/antiferromagnet bilayers
• Magnetic freezing transition in a CoO/Permalloy bilayer revealed by transverse ac susceptibility
• Exchange bias without directional anisotropy in Permalloy/CoO bilayers
• Nearly ideal memristive functionality based on viscous magnetization dynamics