Magnetic damping in ferromagnetic/heavy-metal systems: The role of interfaces and the relation to proximity-induced magnetism

Damping and spin transport in spintronic multilayered systems continues to be a topic of active research. The enhancement of damping in ferromagnet (FM)/spacer layer (SL)/heavy-metal (HM) thin-film systems was studied for Co 25 Fe 75 / SL / Pt with a nonmagnetic (NM) SL of either Au or Cu with variable thickness, in order to understand the correlation with proximity-induced magnetism (PIM) in the HM. Structural, PIM and magnetic damping measurements were undertaken on the same samples. Specifically, secondary ion mass spectroscopy, element specific x-ray magnetic reflectivity and x-ray magnetic circular dichroism at the Pt and Au L 3 edges, and ferromagnetic resonance methods were used. With increasing thickness of a Cu or Au SL directly between the FM and the Pt layer, the Pt PIM and the damping both fall rapidly, with a relationship between damping and PIM that depends on the SL material. The PIM observed in the Au layer showed a complex dependence on the layer thickness, suggesting some hybridization with the Pt. The role of the number and location of interfaces on the damping was demonstrated with the addition of a SL within the Pt layer, which showed that the specific details of the NM/HM interface also affects the damping. The insertion of a Cu SL within the Pt showed a measurable increase in the overall enhancement of the damping while the insertion of a Au SL into Pt had almost no effect on the damping. Together these results demonstrate the role of both PIM and of additional interfaces in the enhancement of damping in FM/HM systems, which is not fully accounted for by existing theory

Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7- δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3

Investigation of spin wave dynamics in Au/CoFeB/Au multilayers with perpendicular magnetic anisotropy

Abstract We have carried out an experimental investigation of the spin-wave dynamics in the Au/CoFeB/Au multilayer consisting of a ferromagnetic film with thicknesses of 0.8, 0.9 and 1.0 nm. We employed the Brillouin light scattering spectroscopy to measure the frequency of the spin waves in dependence on the wave vector. Additionally, we characterized the samples by ferromagnetic resonance measurements. We found that the considered samples exhibit perpendicular magnetic anisotropy with low damping, indicating small pumping effects. Furthermore, we found a nonreciprocal dispersion relation pointing at a non-negligible Dzyaloshinskii–Moriya interaction. These results make the Au/CoFeB/Au multilayer a compelling subject for further analysis and as a potential material for future applications within magnonics

Hard and Soft X-Ray Reflectivity Studies οf (NiFe//Au//Co//Au)10(NiFe//Au//Co//Au)_{10} Magnetic Multilayers

We report on hard and soft X-ray reflectivity investigations of $(Ni_{80}Fe_{20} (2.2 nm)//Au(2.3 nm)//Co(0.8 nm)//Au(2.3 nm))_{10}$ multilayers. Specular reflectivity curves were measured with Cu $K_{α}$ radiation and circularly polarized synchrotron radiation tuned to Co $L_{3}$ and Ni $L_{3}$ absorption edges. Structural properties of the multilayers were determined from the hard X-ray reflectivity curve. Comparison of reflectivity curves taken at different photon energies shows: (i) small difference in peak positions in dependence of reflectivity versus scattering vector q, (ii) different shapes of satellite Bragg peaks, (iii) different ranges of q for appearance of the Kiessig fringes. Analysis of soft X-ray reflectivity curves taken as a function of magnetic field allows to determine magnetic properties of Co and NiFe layer specifically

The Influence of He +

The influence of $He^+$ ion bombardment on magnetoresistance, magnetization reversal and domain structure of sputtered $(Ni_{80}Fe_{20}(2 nm)//Au(2 nm)//Co(0.6 nm)//Au(2 nm))_{10}$ multilayers was investigated. The samples were bombarded using $He^+$(30 keV) ions with fluences D varied from $10^{13}$ to 3×$10^{16}$ $He^+$/$cm^{2}$. With increasing D the following changes in magnetic properties were observed: (i) exponential decay of the saturation field of Co layers, (ii) progressive decrease in magnetoresistance as a result of degradation of Co layers perpendicular anisotropy, (iii) linear decrease in stripe domain period with log(D)

Co/Au multilayers with graded magnetic anisotropy for magnetic field sensing

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich. - This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively

Production of cosmetic emulsion base in SEM-type mechanical mixers

W pracy poddano analizie wpływ liczby sit, przez które wytwarzana była baza emulsji kosmetycznej, na wielkość kropel. Przeanalizowano również układ z pojedynczym sitem, o dwóch różnych wielkościach oczek, pod kątem związku między masowym natężeniem pompy perystaltycznej, a wielkością średnic kropel fazy rozproszonej. Zastosowanie mieszalników typu SEM wpływa korzystnie na właściwości emulsji i pozwoliło uzyskać drobne krople oraz monodyspersyjną emulsję, co jest zjawiskiem pożądanym w przypadku emulsji, które znajdują zastosowanie w kosmetyce.The influence of number of sieves through which the cosmetic emulsion base was produced on a droplet size was analyzed. The single-sieve system with two different mesh sizes was also analyzed, aiming to find the relationship between mass flow rate of peristaltic pump and droplet diameters of dispersed phase. The use of SEM-type mixers positively influences emulsion properties and enables one to obtain fine droplets and monodisperse emulsion which are advantage features in cosmetic emulsions

The Influence of He+He^+ Ion Bombardment on Magnetic Properties of NiFe/Au/Co/Au Multilayers

The influence of $He^+$ ion bombardment on magnetoresistance, magnetization reversal and domain structure of sputtered $(Ni_{80}Fe_{20}(2 nm)//Au(2 nm)//Co(0.6 nm)//Au(2 nm))_{10}$ multilayers was investigated. The samples were bombarded using $He^+$(30 keV) ions with fluences D varied from $10^{13}$ to 3×$10^{16}$ $He^+$/$cm^{2}$. With increasing D the following changes in magnetic properties were observed: (i) exponential decay of the saturation field of Co layers, (ii) progressive decrease in magnetoresistance as a result of degradation of Co layers perpendicular anisotropy, (iii) linear decrease in stripe domain period with log(D)

Proximity induced magnetism and the enhancement of damping in ferromagnetic/heavy metal systems

The relationship between proximity induced magnetism (PIM) at the heavy metal/ferromagnet interface and spin-transport across such interfaces has generated significant debate. To investigate the link between the two, element specific X-ray magnetic circular dichroism and ferromagnetic resonance measurements were made on the same CoFe/Au/Pt and NiFe/Au/Pt thin film samples with varying Au thickness, with complementary SIMS analysis, which shows evidence of Ni diffusion from NiFe into the Pt. An approximately linear relationship is observed between the magnitude of Pt PIM and magnitude of damping enhancement in both systems. The results demonstrate that electronic hybridization of the heavy metal and ferromagnet is required for a full understanding of damping enhancement and interfacial spin-transport for spintronic devices