Spin-resolved off-specular neutron scattering from magnetic domain walls using the polarized ${}^{3}He$ gas spin filter

Abstract

We report on the use of the polarized ${}^3$He gas filter and neutron resonant enhancement techniques for the measurement of spin-polarized diffuse neutron scattering due to ferromagnetic domains. A CoO/Co exchange biased bilayer was grown on a Ti/Cu/$A{l}_2{O}_3$ neutron resonator template. The system is cooled in an applied magnetic field of $H_a=2000$ Oe through the Néel temperature of the antiferromagnet to 10 K where the applied magnetic field is swept as to measure the magnetic hysteresis loop. After the second magnetization reversal at the coercive field $H_{c2}=+230$ Oe, the system is supposed to approach the original magnetic configuration. In order to prove that this is not the case for our exchange biased bilayer, we have measured four off-specular maps I++, I+-, I-+, I-- at $H_a\approx +370$ Oe, where the Co magnetic spins were mostly reversed. They show a striking behavior in the total reflection region: while the nonspin-flip scattering exhibits no diffuse reflectivity, the spin-flip scattering shows strong diffuse scattering at incident angles which satisfy the resonance conditions. Moreover the spin-flip off-specular part of the reflectivity is asymmetric. The I-+ intensity occurs at higher exit angles than the specularly reflected neutrons, and the I+- intensity is shifted to lower angles. Their intensities are noticeably different and there is a splitting of the resonance positions for the up and down neutron spins (${\alpha }_n^{+}\ne {\alpha }_n^{-}$) . Additionally, a strong influence of the stray fields from magnetic domains to the resonance splitting is observed.

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• Exchange bias effect of ferro-/antiferromagnetic heterostructures
• Optically Polarized ${}^3$He
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• Magnetic induction and domain walls in magnetic thin films at remanence
• Polarized neutron channeling in weakly magnetic films
• Chirality of Bloch domain walls in exchange biased CoO/Co bilayer seen by waveguide-enhanced neutron spin-flip scattering
• Divergence of neutron microbeams from planar waveguides