Nanostructures Defined by The Local Oxidation of Ferromagnetic GaMnAs Layer

The results of Local Anodic Oxidation (LAO) on the thin GaMnAs layers are reported. The ferromagnetic GaMnAs layers were prepared by low temperature MBE growth in a Veeco Mod Gen II machine. The LAO process was performed with the AFM microscope Smena NT-MDT placed in the sealed box with the controlled humidity in the range 45-80%. The oxide was grown in the semi-contact mode of the AFM. Sample was positively biased with respect to the AFM tip with the bias from 6 to 24 V. The conductive diamond coated AFM tips with the radius 30 nm were utilized for the oxidation. The tip speed during the oxidation was changed from 400 nm/s to 1.5 μm/s. The tip force was also changed during the oxidation. The height of oxide nanolines increases with applied voltage from 3 to 18 nm. The width of these lines was approximately 100 nm at half of the maximum

Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn3Sn

Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinarily difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representatives of this class of materials—Mn3Sn. We demonstrate that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well-defined domain pattern at room temperature based on heat assisted recording principle. Our study opens up a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution

Ceramic-Chromium Hall Sensors for Environments with High Temperatures and Neutron Radiation

Ceramic-chromium Hall sensors represent a temperature and radiation resistant alternative to Hall sensors based on semiconductors. Demand for these sensors is presently motivated by the ITER and DEMO nuclear fusion projects. The developed ceramic-chromium Hall sensors were tested up to a temperature of 550 °C and a magnetic field of 14 T. The magnitude of the sensitivity of the tested sensor was 6.2 mV/A/T at 20 °C and 4.6 mV/A/T at 500 °C. The sensitivity was observed to be weakly dependent on a temperature above 240 °C with an average temperature coefficient of 0.014%/°C and independent of the magnetic field with a relative average deviation below the measurement accuracy of 0.086%. A simulation of a neutron-induced transmutation was performed to assess changes in the composition of the chromium. After 5.2 operational years of the DEMO fusion reactor, the transmuted fraction of the chromium sensitive layer was found to be 0.27% at the most exposed sensor location behind the divertor cassette with a neutron fluence of 6.08 × 1025 n/m2. The ceramic-chromium Hall sensors show the potential to be suitable magnetic sensors for environments with high temperatures and strong neutron radiation

Ceramic-Chromium Hall Sensors for Environments with High Temperatures and Neutron Radiation

Ceramic-chromium Hall sensors represent a temperature and radiation resistant alternative to Hall sensors based on semiconductors. Demand for these sensors is presently motivated by the ITER and DEMO nuclear fusion projects. The developed ceramic-chromium Hall sensors were tested up to a temperature of 550 °C and a magnetic field of 14 T. The magnitude of the sensitivity of the tested sensor was 6.2 mV/A/T at 20 °C and 4.6 mV/A/T at 500 °C. The sensitivity was observed to be weakly dependent on a temperature above 240 °C with an average temperature coefficient of 0.014%/°C and independent of the magnetic field with a relative average deviation below the measurement accuracy of 0.086%. A simulation of a neutron-induced transmutation was performed to assess changes in the composition of the chromium. After 5.2 operational years of the DEMO fusion reactor, the transmuted fraction of the chromium sensitive layer was found to be 0.27% at the most exposed sensor location behind the divertor cassette with a neutron fluence of 6.08 × 1025 n/m2. The ceramic-chromium Hall sensors show the potential to be suitable magnetic sensors for environments with high temperatures and strong neutron radiation

Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn₃Sn

Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinarily difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representatives of this class of materials-Mn3Sn. We demonstrate that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well-defined domain pattern at room temperature based on heat assisted recording principle. Our study opens up a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution.publishe

Synthesis and physical properties of uranium thin-film hydrides UH2 and \b{eta}-UH3

Formation of thin uranium hydrides films, UH2 and \b{eta}-UH3, synthesized by a reactive dc sputtering of uranium metal, was explored using variable deposition conditions. Obtained stable oxygen-free hydride films were studied by a variety of methods, both in situ (photoelectron spectroscopy - XPS), and ex-situ (x-ray diffraction - XRD, transmission electron microscopy - TEM), electrical resistivity, and magnetometry). Both types of hydrides are ferromagnetic, the Curie temperatures of UH2 and \b{eta}-UH3 are approx. 120 and 170 K, respectively. Ferromagnetism in the thin films is robust and does not depend on structure details while electrical resistivity data reflect disorder in both types of hydrides