Spin waves modes in cobalt nanowires arrays

Cobalt nanowires (NWs) of 40-50 nm average diameter and several micrometers in length were elaborated by electrodeposition process in alumina templates. X-ray diffraction measurements show that all the NWs present a heterogeneous crystalline structure with hcp phase that can be tuned by an appropriate choice of the electrolyte pH. A complex evolution of the magnetic coercivity and squareness with pH is observed in connection with that of the hcp c-axis of the crystalline structure. The spin waves (SWs) propagating into the NWs were investigated by means of the Brillouin light scattering technique. A detailed analysis of the SW spectra allows the identification of dipolar and exchange nature modes propagating within the NWs. Their frequency behavior is successfully described by means of analytical models

Interfacial Dzyaloshinskii-Moriya Interaction, Perpendicular Magnetic Anisotropy and damping in CoFeB/oxide-based systems

International audiencePerpendicular magnetic anisotropy (PMA), spin pumping induced damping and interfacial Dzyaloshinskii-Moriya interaction (iDMI), which are spin-orbit coupling-related phenomena of utmost importance for applications, were experimentally investigated in as grown and 225°C annealed CoFeB/PtOx, CoFeB/TaOx and Ta/CoFeB/TaOx systems by means of vibrating sample magnetometry, microstrip ferromagnetic resonance and Brillouin light scattering techniques. By varying Co8Fe72B20 (CoFeB) thickness in the range 0.8-10 nm, the effect of Ta buffer layer on anisotropy and damping was first studied, where a large surface magnetic anisotropy (Ks=2.1±0.16 erg/cm2) was measured in the unbuffered CoFeB/TaOx(0.8nm) system most likely due to their higher roughness induced by the substrate. Ks degrades significantly for CoFeB film thickness below 2 nm where spontaneous perpendicular magnetization was found to be impossible without Ta buffer layer. PMA, iDMI and damping of as-deposited and 225°C annealed CoFeB(1.5 nm)/PtOx systems were measured as a function of PtOx thickness in the range 0.7-1.6 nm. Their strong dependence versus the PtOx thickness was attributed to the decrease of the magnetic dead layer as PtOx thickness increases. Linear dependence of damping versus PMA constant was obtained confirming their relation with the spin orbit coupling. Moreover, annealing increases PMA and the effective mixing conductance probably due to the enhancement of the CoFeB crystal structure and interfaces

Magnetic properties of Mn-implanted 6H-SiC single crystal

The electronic and magnetic structures of Mn-doped 6H-SiC have been investigated using ab initio calculations. Various configurations of Mn sites and vacancy types have been considered. The calculations showed that a substitutional Mn atom at either Si or C sites possesses a magnetic moment. The Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. The magnetic properties of ferromagnetically and antiferromagnetically coupled pair of Mn atoms in the presence of vacancies have also been explored. Our calculations show that antiferromagnetically coupled pair of Mn atoms at Si sites with neighboring C vacancy is magnetically more stable. Relaxation effects were also studied. The results are correlated to the measured magnetic properties obtained for Mn-implanted 6H-SiC for various Mn concentrations. (C) 2012 American Institute of Physics

Experimental study of spin-wave dispersion in Py/Pt film structures in the presence of an interface Dzyaloshinskii-Moriya interaction

Équipe 101 : Nanomagnétisme et électronique de spinInternational audienceBrillouin light scattering (BLS), complemented by ferromagnetic resonance (FMR) characterization, has been used for studying spin-wave (SW) propagation in Py(L)/Pt(6-nm) bilayers of various Py thicknesses (4 nm <= L <= 10 nm). The FMR measurements allowed determination of the pertinent magnetic parameters and revealed the existence of a normal surface anisotropy. A pronounced asymmetry of Damon-Eshbach (DE) wave frequencies has been evidenced by BLS. Therefore, the difference between Stokes and anti-Stokes DE frequencies has been measured versusSWwave number for all the samples. A detailed discussion about the origin of this frequency difference is reported, which concludes that this is due to interface Dzyaloshinskii-Moriya interaction (IDMI)

The interfacial nature of proximity-induced magnetism and the Dzyaloshinskii-Moriya interaction at the Pt/Co interface

The Dzyaloshinskii-Moriya interaction has been shown to stabilise Nèel domain walls in magnetic thin films, allowing high domain wall velocities driven by spin current effects. The interfacial Dzyaloshinskii-Moriya interaction (IDMI) occurs at the interface between ferromagnetic and heavy metal layers with strong spin-orbit coupling, but details of the interaction remain to be understood and the role of proximity induced magnetism (PIM) in the heavy metal is unknown. Here IDMI and PIM are reported in Pt determined as a function of Au and Ir spacer layers in Pt/Co/Au,Ir/Pt. Both interactions are found to be sensitive to sub-nanometre changes in the spacer thickness, correlating over sub-monolayer spacer thicknesses, but not for thicker spacers where IDMI continues to change even after PIM is lost