Abstract
The in-plane magnetic structure of a layered system composed of polycrystalline grains smaller than the ferromagnetic exchange length was studied to elucidate the mechanism controlling the magnetic properties considerably different from the bulk using polarized neutron scattering under grazing incidence geometry. The measured result, together with quantitative analysis based on the distorted wave Born approximation, showed that the in-plane length of the area with a uniform orientation of moments ranging from 0.5–1.1 μ m was not significantly varied during the process of demagnetization followed by remagnetization. The obtained behavior of moments is in good agreement with the two-dimensional random anisotropy model where coherent magnetization rotation is dominant.
Highlights
Layered magnetic structures have drawn considerable interests because of their attractive and useful magnetic properties not seen in the bulk such as exchange coupling between layers, giant magnetoresistance, and tunnel magnetoresistance [1,2,3]
The measured values were normalized with the volume of the Fe layers, using an Fe thickness of 3.8 nm where the thickness of the “magnetically-dead” layers was determined as 1.2 nm per a period by the result of the polarized neutron reflectivity measurement shown in Section 3.2 and subtracted from a nominal Fe thickness of 5.0 nm calculated by the sputtering rate
We performed the polarized off-specular neutron scattering (OSS) and grazing-incidence small-angle neutron scattering (GISANS) measurements for the Fe/Si multilayer composed of polycrystalline grains smaller than the ferromagnetic exchange length to understand what was responsible for the magnetic properties different from the bulk
Summary
Layered magnetic structures have drawn considerable interests because of their attractive and useful magnetic properties not seen in the bulk such as exchange coupling between layers, giant magnetoresistance, and tunnel magnetoresistance [1,2,3]. The idea of the formation and movement of domain walls disagrees with the measured data when the grain size becomes comparable to or smaller than the ferromagnetic exchange length. In this case, the exchange interaction between neighboring moments prevails over the magneto-crystalline anisotropies. The information on the behavior of moments, the in-plane magnetic structure, during the demagnetization and remagnetization is needed to demonstrate whether this model agrees with our system composed of polycrystalline grains smaller than the ferromagnetic exchange length
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