Magnetoresistance Anisotropy of Polycrystalline Cobalt Films: Geometrical-Size- and Domain-Effects

The magnetoresistance (MR) of 10 nm to 200 nm thin polycrystalline Co-films, deposited on glass and insulating Si(100), is studied in fields up to 120 kOe, aligned along the three principal directions with respect to the current: longitudinal, transverse (in-plane), and polar (out-of-plane). At technical saturation, the anisotropic MR (AMR) in polar fields turns out to be up to twice as large as in transverse fields, which resembles the yet unexplained geometrical size-effect (GSE), previously reported for Ni- and Permalloy films. Upon increasing temperature, the polar and transverse AMR's are reduced by phonon-mediated sd-scattering, but their ratio, i.e. the GSE remains unchanged. Basing on Potters's theory [Phys.Rev.B 10, 4626(1974)], we associate the GSE with an anisotropic effect of the spin-orbit interaction on the sd-scattering of the minority spins due to a film texture. Below magnetic saturation, the magnitudes and signs of all three MR's depend significantly on the domain structures depicted by magnetic force microscopy. Based on hysteresis loops and taking into account the GSE within an effective medium approach, the three MR's are explained by the different magnetization processes in the domain states. These reveal the importance of in-plane uniaxial anisotropy and out-of-plane texture for the thinnest and thickest films, respectively.Comment: 10 pages, 9 figure

First operation of the KATRIN experiment with tritium

The determination of the neutrino mass is one of the major challenges in astroparticle physics today. Direct neutrino mass experiments, based solely on the kinematics of β β -decay, provide a largely model-independent probe to the neutrino mass scale. The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to directly measure the effective electron antineutrino mass with a sensitivity of 0.2 eV 0.2 eV (90% 90% CL). In this work we report on the first operation of KATRIN with tritium which took place in 2018. During this commissioning phase of the tritium circulation system, excellent agreement of the theoretical prediction with the recorded spectra was found and stable conditions over a time period of 13 days could be established. These results are an essential prerequisite for the subsequent neutrino mass measurements with KATRIN in 2019

Quantitative Long-Term Monitoring of the Circulating Gases in the KATRIN Experiment Using Raman Spectroscopy.

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims at measuring the effective electron neutrino mass with a sensitivity of 0.2 eV/c2, i.e., improving on previous measurements by an order of magnitude. Neutrino mass data taking with KATRIN commenced in early 2019, and after only a few weeks of data recording, analysis of these data showed the success of KATRIN, improving on the known neutrino mass limit by a factor of about two. This success very much could be ascribed to the fact that most of the system components met, or even surpassed, the required specifications during long-term operation. Here, we report on the performance of the laser Raman (LARA) monitoring system which provides continuous high-precision information on the gas composition injected into the experiment's windowless gaseous tritium source (WGTS), specifically on its isotopic purity of tritium-one of the key parameters required in the derivation of the electron neutrino mass. The concentrations cx for all six hydrogen isotopologues were monitored simultaneously, with a measurement precision for individual components of the order 10-3 or better throughout the complete KATRIN data taking campaigns to date. From these, the tritium purity, εT, is derived with precision of <10-3 and trueness of <3 × 10-3, being within and surpassing the actual requirements for KATRIN, respectively

Quantitative Long-Term Monitoring of the Circulating Gases in the KATRIN Experiment Using Raman Spectroscopy.

The Karlsruhe Tritium Neutrino (KATRIN) experiment aims at measuring the effective electron neutrino mass with a sensitivity of 0.2 eV/c2, i.e., improving on previous measurements by an order of magnitude. Neutrino mass data taking with KATRIN commenced in early 2019, and after only a few weeks of data recording, analysis of these data showed the success of KATRIN, improving on the known neutrino mass limit by a factor of about two. This success very much could be ascribed to the fact that most of the system components met, or even surpassed, the required specifications during long-term operation. Here, we report on the performance of the laser Raman (LARA) monitoring system which provides continuous high-precision information on the gas composition injected into the experiment's windowless gaseous tritium source (WGTS), specifically on its isotopic purity of tritium-one of the key parameters required in the derivation of the electron neutrino mass. The concentrations cx for all six hydrogen isotopologues were monitored simultaneously, with a measurement precision for individual components of the order 10-3 or better throughout the complete KATRIN data taking campaigns to date. From these, the tritium purity, εT, is derived with precision of <10-3 and trueness of <3 × 10-3, being within and surpassing the actual requirements for KATRIN, respectively