A. A. Parizzi | Searcharxiv

arXiv2010

Magnetic Structure in Fe/Sm-Co Exchange Spring Bilayers with Intermixed Interfaces

The depth profile of the intrinsic magnetic properties in an Fe/Sm-Co bilayer fabricated under nearly optimal spring-magnet conditions was determined by complementary studies of polarized neutron reflectometry and micromagnetic simulations. We found that at the Fe/Sm-Co interface the magnetic properties change gradually at the length scale of 8 nm. In this intermixed interfacial region, the saturation magnetization and magnetic anisotropy are lower and the exchange stiffness is higher than values estimated from the model based on a mixture of Fe and Sm-Co phases. Therefore, the intermixed interface yields superior exchange coupling between the Fe and Sm-Co layers, but at the cost of average magnetization.

cond-mat.mtrl-sci↗

arXiv2001

Decoupled Moderators - Do we always need them? or: A New Approach for Pulse Shaping

At a spallation neutron source, the wavelength of a neutron is generally determined by its time-of-flight (TOF) from the source to the detector. The achievable precision is ultimately limited by the non-zero emission time-width of the source/moderator system. Particularly, coupled moderators that are used to produce high intensity cold neutron beams show long "tails" in the intensity/time distribution for all wavelengths. For this reason much less intense decoupled moderators are often used for instruments that require high resolution. We present here a novel technique for dynamic energy filtering of thermal and cold polarized neutron beams. The device consists of a polarizer/analyzer system and an energy-selective spin-resonance flipper. By drifting its resonance condition in synchronization with the TOF, the filter controls the energy resolution of a broad bandwidth TOF neutron pulse. Calculations show that substantial resolution gains are obtainable by applying this technique to a TOF neutron reflectometer.

physics.ins-det↗