Spin-resolved off-specular neutron scattering from magnetic domain walls using the polarized [formula omitted] 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/Al 2O 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 ≈+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 ( α n +≠ α n −). Additionally, a strong influence of the stray fields from magnetic domains to the resonance splitting is observed.