5 research outputs found
Interfacial Dzyaloshinskii-Moriya interaction in epitaxial W/Co/Pt multilayers
Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered
ferromagnetic films gives rise to non-colinear spin structures stabilizing
magnetization configurations with nontrivial topology. In this work
magnetization reversal, domain structure, and strength of DMI are related with
the structure of W/Co/Pt multilayers grown by molecular beam epitaxy. Applied
growth method enables fabrication of layered systems with higher crystalline
quality than commonly applied sputtering techniques. As a result, a high value
of D coefficient was determined from the aligned magnetic domain stripe
structure, substantially exceeding 2 mJ/m2. The highest value of DMI value
D = 2.64mj/m2 and strength of surface DMI parameter DS = 1.83pJ/m for
N=10 has been observed. Experimental results coincide precisely with those
obtained from structure based micromagnetic modelling and density functional
theory calculations performed for well-defined layered stacks. This high value
of DMI strength originates from dominating contributions of the interfacial
atomic Co layers and additive character from both interface types
Cryogenic temperature growth of Sn thin films on ferromagnetic Co(0001)
Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin-polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator (TI) materials is the large defect concentration which leads a high background carrier concentration. Elemental tin in its α-phase is a room temperature topological semimetal, which is intrinsically less prone to defect-related shortcomings. Recently, the growth of ultrathin α-Sn films on ferromagnetic Co surfaces has been achieved, however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α-Sn films on Co at cryogenic temperatures was explored. Very low-temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ∼3 atomic layers, above which the film partially transforms into the undesired β-phase, remains the same as for room-temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact
Magnetic properties, martensitic and magnetostructural transformations of ferromagnetic Ni-Mn-Sn-Cu shape memory alloys
The influence of Cu doping on structural and magnetic properties of Ni50-xMn36Sn14-
yCux, y (x=0, 1,2 and y=1 at. %) ribbons has been investigated. The crystalline structures of the
alloys were resolute by X-ray diffraction (XRD). It is found that the addition of Cu for Ni
stabilizes austenite phase, whereas, replacing small amount of Cu for Sn stabilizes modulated
martensite phase. Differential scanning calorimetry measurements have proved the
characteristic transformation temperatures.The financial support from MAT2016-675967-P MINECO project is acknowledged. This work
was partially supported by the national Science Centre of Poland – project
2018/31/B/ST7/04006.Postprint (author's final draft
Electronic properties of topological semimetal investigated by transport and ARPES
We have performed electron transport and ARPES measurements on single
crystals of transition metal dipnictide TaAs2 cleaved along the (
0 1) surface which has the lowest cleavage energy. A Fourier transform of the
Shubnikov-de Haas oscillations shows four different peaks whose angular
dependence was studied with respect to the angle between the magnetic field and
the [ 0 1] direction. The results indicate the elliptical shape
of the Fermi surface cross-sections. Additionally, a mobility spectrum analysis
was carried out, which also reveals at least four types of carriers
contributing to the conductance (two kinds of electrons and two kinds of
holes). ARPES spectra were taken on freshly cleaved ( 0 1)
surface and it was found that bulk states pockets at the constant energy
surface are elliptical, which confirms the magnetotransport angle dependent
studies. First-principles calculations support the interpretation of the
experimental results. The theoretical calculations better reproduce the ARPES
data if the theoretical Fermi level is increased, which is due to a small
n-doping of the samples. This shifts the Fermi level closer to the Dirac point,
allowing to investigate the physics of the Dirac and Weyl points, making this
compound a platform for the investigation of the Dirac and Weyl points in
three-dimensional materials.Comment: 12 pages, 13 figure