Optimization of ruthenium as a buffer layer for non-collinear antiferromagnetic Mn<inf>3</inf>X films

Two thin film deposition routes were studied for the growth of high quality single crystalline Ru (0001) epitaxial films on c-Al2O3 substrates using RF-magnetron sputtering. Such films are very important as buffer layers for the deposition of epitaxial non-collinear antiferromagnetic Mn3X films. The first route involved depositing Ru at 700 °C, leading to a smooth 30 nm thick film. Although, high resolution X-ray diffraction (HRXRD) revealed twinned Ru film orientations, the in-situ post-annealing eliminated one orientation, leaving the film orientation aligned with the substrate, with no in-plane lattice rotation and a large lattice mismatch (13.6%). The second route involved deposition of Ru at room temperature followed by in-situ post-annealing at 700 °C. Transmission electron microscopy confirmed a very high quality of these films, free of crystal twinning, and a 30° in-plane lattice rotation relative to the substrate, resulting in a small in-plane lattice mismatch of –1.6%. X-ray reflectivity demonstrated smooth surfaces for films down to 7 nm thickness. 30 nm thick high quality single-crystalline Mn3Ga and Mn3Sn films were grown on top of the Ru buffer deposited using the second route as a first step to realize Mn3X films for antiferromagnetic spintronics applications.H2020-MSCA-ITN-2014 SELECTA (grant agreement no. 642642 of the European Commission)

Practical Use of a Liquid Helium-Free Superconducting Magnet(Magnet Technology)

A cryocooler-cooled 4.6 T superconducting magnet with a 38 mm room temperature bore, which consists of a low-T_c Nb_3Sn coil and high-T_c Bi_2Sr_2Ca_2Cu3O_ current leads, has been working in vacuum for about 18000 cooling hours without trouble, It is found that the high-T_c current leads can hold excellent superconducting properties for a long enough time to be practically used. As a next step, we have succeeded in the construction of a l0.7 T-52 mm room temperature bore and a 5.7 T-220 mm room temperature bore liquid helium-free superconducting magnet

Extensive study of giant magnetoresistance properties in half-metallic Co₂(Fe,Mn)Si-based devices

Fully epitaxial Co₂FexMn1- xSi(CFMS)/Ag/Co₂FexMn1 -xSi current-perpendicular-to-plane giant magnetoresistive devices with various Fe/Mn ratios x and top CFMS layer thicknesses t CFMS were prepared. The highest magnetoresistance (MR) ratios, 58% at room temperature and 184% at 30 K, were observed in the sample with x = 0.4 and tCFMS = 3 nm. Enhancement of interface spin-asymmetry was suggested for x = 0.4 compared with that at x = 0. A MR ratio of 58% was also observed even in a very thin trilayer structure, CFMS(4 nm)/Ag(3 nm)/CFMS(2 nm), which is promising for a next-generation magnetic read sensor for high-density hard disk drives. © 2012 American Institute of Physics.Y. Sakuraba, M. Ueda, Y. Miura, K. Sato, S. Bosu, K. Saito, M. Shirai, T. J. Konno, and K. Takanashi, "Extensive study of giant magnetoresistance properties in half-metallic Co₂(Fe,Mn)Si-based devices", Appl. Phys. Lett. 101, 252408 (2012) https://doi.org/10.1063/1.4772546