The magnetic interfacial properties of an exchange biased nanocrystalline Ni80Fe20/α-Fe2O3 bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

• Published in: Japanese Journal of Applied Physics 2020-01, Vol.59, p.SAAC03-1
• Main Authors: Causer, Grace L, Cortie, David L, Callori, Sara J, Manna, Palash K, van Lierop, Johan, Lee, Yi-Ju, Wang, Xiaolin L, Lin, Ko-Wei, Klose, Frank
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Bias; Bilayers; Computer simulation; Exchanging; Ferromagnetism; Grain boundaries; Interface roughness; Interfacial properties; Iron oxides; Magnetic measurement; Magnetic properties; Monte Carlo simulation; Morphology; Nanocrystals; Reflectometry
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/1347-4065/ab4603

The strength of exchange bias can be influenced by interface roughness and antiferromagnetic morphology. Here, we studied the interface profile of an exchange biased, nanocrystalline Ni80Fe20/α-Fe2O3 bilayer. Magnetometry determined the bilayer's exchange bias is observed below a blocking temperature of 75 K. Polarized neutron reflectometry measurements revealed the Ni80Fe20 layer was fully saturated to yield a net-moment of 0.95 μB/atom, while the majority of the Fe2O3 layer exhibited zero net-magnetization with the exception of the interfacial region with an uncompensated moment between 0.5 and 1.0 μB/Fe2O3. Monte Carlo simulations of a ferromagnetic/antiferromagnetic bilayer incorporating a granular antiferromagnet indicate that an extrinsic uncompensated moment of ~1.0 μB/Fe2O3 can arise from grain boundary disorder. The size of the modeled moment is equivalent to the experimental value, and comparable with previous calculations. Furthermore, unlike intrinsic uncompensated spins, it is found that the disorder-induced moment in the granular antiferromagnet is not destroyed by interface roughness.