arXiv subjects

S. Mattauch

Publications and source records attributed to S. Mattauch.

4 recordsLinked to original sources

arXiv2020

Structural, Electronic, and Magnetic Properties of HiPIMS Grown Co-N Thin Films

We studied the growth behavior, structural, electronic, and magnetic properties of cobalt nitride (Co-N) thin films deposited using direct current (dc) and high power impulse magnetron sputtering (HiPIMS) processes. The N$_2$ partial gas flow (\pn) was varied in close intervals to achieve the optimum conditions for the growth of tetra cobalt nitride (\tcn) phase. We found that Co-N films grown using HiPIMS process adopt (111) orientation as compared to the growth taking place along the (100) direction in the dcMS process. It was observed that HiPIMS grown Co-N~films were superior in terms of crystallite size and uniform surface morphology. The local structure of films was investigated using x-ray absorption fine structure (XAFS) measurements. We found that the high energy of adatoms in the HiPIMS technique assisted in the greater stabilization of fcc-Co and novel \tcn~phase relative to the dcMS process. Magnetic properties of Co-N thin films were studied using magneto-optical Kerr effect, vibrating sample magnetometry and polarized neutron reflectivity. It was found that though the saturation magnetization remains almost similar in films grown by dcMS or HiPIMS processes, they differ in terms of their magnetic anisotropy. Such variation can be understood in terms of differences in the growth mechanisms in dcMS and HiPIMS processes affecting the local structure of resulting \tcn~phase.

cond-mat.mtrl-sci↗

arXiv2017

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å$^{-1}$. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

physics.ins-det↗

arXiv2015

HERITAGE: the concept of a giant flux neutron reflectometer for the exploration of 3-d structure of free-standing and solid interfaces in thin films

The instrumental concept of HERITAGE - a reflectometer with a horizontal sample geometry - fitted to the long pulse structure of a neutron source is presented. It is dedicated on creating a new class of reflectometers achieving the unprecedentedly high flux for classical specular reflectometry combined with off-specular reflectometry and grazing incidence small-angle scattering (GISANS), thus resulting in a complete 3-d exploration for lateral structures in thin films. This is achieved by specially designed neutron guides: in the horizontal direction (perpendicular to the scattering plane) it has an elliptic shape and focusses neutrons onto the sample. In the vertical direction it has a multichannel geometry providing a smooth divergence distribution at the sample while accepting the whole beam from a compact high-brilliance flat moderator. The modular collimation setup of HERITAGE provides an extremely high flexibility in respect to sample geometries and environments, including the possibility to study all types of solid and liquid interfaces statically or kinetically. Moreover, the use of multiple beam illumination allows for reflectivity and GISANS measurements at liquid interfaces both from above and below without any movement of the sample. This concept assures that reflectivity and GISANS measurements can be performed in its best way as the maximum possible and usable flux is delivered to the sample, outperforming all present-day or already planned for the ESS reflectometers and GISANS setups in flux and in measuring time for standard samples.

physics.ins-det↗

arXiv2010

High level of $^3$He polarization of 81\% Maintained in an on-beam $^3$He spin filter using SEOP

Maintaining high levels of 3He polarization over long periods of time is important to many areas of fundamental and particle beam physics. Long measurement times are often required in such experiments and the data quality is a function of the 3He polarization. This is the case for neutron scattering where the 3He can be used to analyze the spin of a scattered neutron beam and relatively small fluxes of polarized neutrons leads to experiment times longer than several days. Consequently the Jülich Centre for Neutron Science (JCNS) is developing spin-exchange optical pumping (SEOP) systems capable of polarizing the 3He gas in place on a typical neutron instrument. Using a polarizer device we constructed a high level of 3He polarization of 81 % \pm2% was maintained with good time stability. Such levels of polarization maintained over time will be able to reduce the measurement times for such experiments and eliminate time dependent data corrections.

physics.ins-det↗