Interdiffusion and magnetism of the Co/Rh interface studied by magnetization induced second harmonic generation (original) (raw)
Related papers
Magnetic second-harmonic generation from interfaces and nanostructures
2010
Magneto-optic techniques provide non-contact and non-destructive characterization of magnetic materials. This includes embedded magnetic nanostructures, which are accessible due to the large penetration depth of optical radiation. The linear magneto-optic Kerr effect is widely used in the growth and characterization of ultra-thin magnetic films and can show monolayer sensitivity. Nonlinear magnetic second-harmonic generation (MSHG) is a more difficult and expensive technique but, uniquely, can measure the surface and interface magnetism of centrosymmetric magnetic films with sub-monolayer sensitivity. MSHG is briefly reviewed and examples from high symmetry interfaces and nanostructures described. Low symmetry structures are more difficult to characterize, however, because of the large number of tensor components that may contribute to the signal. An important class of low symmetry systems exploits vicinal substrates to grow aligned magnetic nanostructures by self-organization. These structures have a high proportion of magnetic step or edge atoms relative to the terrace atoms, and the overall magnetic response is expected to contain significant contributions from these different magnetic regions. It is shown that contributions from these different regions can be identified using normal A c c e p t e d m a n u s c r i p t -2 -incidence (NI) MSHG. This new approach is used to determine hysteresis loops from Au-capped Fe monolayers grown on a vicinal W(110) substrate. Temperature-dependent studies of the MSHG contrast also allow Curie temperatures to be determined. This experimental procedure and phenomenology opens up low symmetry magnetic interfaces and aligned nanostructures to characterization by MSHG.
Magnetization-induced optical third-harmonic generation in Co and Fe nanostructures
Physical Review B, 2006
Magnetization-induced optical third-harmonic generation (MTHG) is observed in magnetic nanostructures: Co and F e nanolayers and granular films containing Co nanoparticles. Magnetizationinduced variations of the MTHG characteristics in these nanostructures exceed the typical values of linear magneto-optical Kerr effect by at least an order of magnitude: the maximum of magnetic contrast in the MTHG intensity is up to 0.2, the angle of polarization rotation for MTHG is 10 • and the relative phase shift is up to 100 • .
Physical Review B, 2007
We have studied the magnetic field dependences of magnetic optical second harmonic generation ͑SHG͒ in MBE-grown Fe/ Cr/ Fe/ Ag/ GaAs͑100͒ heterostructures displaying both bilinear and biquadratic interlayer exchange coupling. The magnetic field H was applied in the ͑100͒ surface plane along both easy ͓͑001͔͒ and hard ͓͑110͔͒ axes of the in-plane fourfold magnetic anisotropy. The SHG has been measured in reflection at near normal incidence for different polarization combinations ͑pp , ps , ss , sp͒ of the fundamental and second harmonic light in longitudinal and transversal geometries. The magnetic field variation of the SHG signal clearly reflects the field-induced transformations of the magnetic state at the interfaces in the trilayer. It strongly depends on the configuration of light polarization, experimental geometry ͑longitudinal or transver-sal͒, and orientation of the magnetic field H relative to the crystal axes. In contrast to linear magneto-optical Kerr effect, which is odd in magnetic field, magnetic SHG is either even in H or does not display a definite parity at all, depending on the polarization configuration. We interpret the data based on a model accounting for nonmagnetic and magnetic contributions to SHG from the surface and interfaces described by C 4v point symmetry. Taking into account the changes of the mutual orientation of interfacial magnetizations allows us to describe the general features of the measured field dependences of SHG.
Journal of Physics: Condensed Matter, 2007
Surface-and interface-sensitive optical techniques, such as optical secondharmonic generation (SHG), allow the buried interfacial structure of centrosymmetric materials to be explored through thin capping layers, and magnetic SHG (MSHG) extends this to magnetic interfaces. However, the variation of the MSHG intensity with magnetic field does not measure hysteresis loops directly, because the loops are displaced by an amount dependent on the crystallographic response and its phase difference with respect to the magnetic response, and also because there is a quadratic magnetization contribution to the SH intensity that may be significant. Two new procedures are reported for extracting hysteresis loops directly from the MSHG intensity. The first is applicable to all magnetic interfaces, including exchange-biased structures, where the saturation magnetization for positive and negative magnetic fields is equal and opposite. The second applies to all centrosymmetric hysteresis loops. These procedures correct for the quadratic response, allowing experimental geometries to be chosen that maximize the magnetic contribution, thus improving the signal-to-noise ratio and the sensitivity of the technique.
In-depth selectivity of the magnetic second-harmonic generation of light in a multilayer structure
Physical Review B, 2004
The in-depth selectivity of magneto-optical second-harmonic generation (MSHG) is investigated in the CoO/ Co/ NiO/ Fe-Ni/ Cu film structure. The p in p out MSHG is essentially selective to only one NiO/ Fe-Ni buried magnetic interface, whereas p in s out and s in p out MSHG is shown to be magnetically sensitive to all interfaces. MSHG data are also compared to the usual longitudinal Kerr effect. Symmetry arguments and calculations point out that the observed in-depth MSHG selectivity is mainly linked to the electric field profile of the incident radiation through the multilayer structure.
Magnetization-induced second harmonic generation of light by exchange-coupled magnetic layers
2005
A longitudinal magneto-optical Kerr effect and magnetization-induced second-harmonic generation (MSHG) of light (at 2omega) have been measured in a SiO2/Fe96Si4/Dy30Fe58Co12/glass exchange-coupled magnetic bilayer system with competitive anisotropies. Theoretical MSHG predictions in this structure that give rise to an effect proportional to magnetization components and that are allowed by an electric dipole mechanism are reported and discussed. The magnitude of the MSHG effect depends on the electric field of the incoming radiation at each interface and on the corresponding incoming (at omega) and outgoing (at 2omega) Fresnel coefficients. It is demonstrated that transverse pp MSHG selectively probes the magnetization of the first SiO2/Fe96Si4 interface, while transverse sp and longitudinal ps MSHG is sensitive, but less selectively, to the Fe96Si4/Dy30Fe58Co12 interface that supports a planar magnetic domain wall. (p and s are the usual parallel and perpendicular polarizations to t...
Magnetization and ferromagnetic resonance studies in Co/V multilayers
Physica B-condensed Matter, 2004
The magnetic properties of evaporated Co/V multilayer films have been studied by superconducting quantum interference device magnetometer and ferromagnetic resonance (FMR). The magnetization follows a quasi-linear temperature dependence, which reverts to a T 3=2 dependence further into the bulk. We attribute the quasi-linear temperature behavior to surface spin-wave modes created by a perpendicular surface anisotropy at the interface. The FMR spectra are obtained with the applied magnetic field parallel and perpendicular to the film plane at 300 K. The FMR linewidth of uniform mode, DH > ; for the perpendicular geometry, depends on the thickness of Co layer as t À2
Layer-selective spectroscopy of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">mml:mrowmml:miFemml:mo∕mml:miGamml:miAs(001): Influence of the interface on the magnetic properties
Physical Review B, 2005
We present magneto-optic Kerr effect, x-ray photoelectron spectroscopy, and x-ray magnetic circular dichroism data from epitaxial thin ferromagnetic film grown onto GaAs͑001͒-͑4 ϫ 6͒. By seeding a half monolayer of Co in an Fe double wedge with a total thickness of six monolayers, we introduced a magnetic marker, which, similarly to Mössbauer spectroscopy, allows us to probe the magnetic and chemical properties across the ferromagnetic film in a layer-dependent analysis. The long-range magnetization is found to persist within the Fe overlayer at any depth, until a reduction is observed at the interface with GaAs. Correspondingly the spin magnetic moment is maximum at the center of the film and is reduced both at the interface and at the surface. We found also an enhancement of the orbital magnetic moment and orbit-to-spin magnetic-moment ratio near the interface with the GaAs substrate. Further, an uneven segregation ͑diffusion͒ between Ga and As has been found, and its influence on magnetic properties is discussed.
Journal of Applied Physics, 2008
The interface and bulk magnetization dynamics of single-crystalline, wedge-shaped Fe͑001͒ thin films with Cr cap layers have been studied by time-resolved magneto-optical Kerr effect ͑MOKE͒ and time-resolved magnetization-induced second harmonic generation ͑MSHG͒ using an all-optical pump-probe technique. We observed long-lived ͑Ϸ1 ns͒ MOKE and MSHG oscillations excited by ultrashort ͑Ϸ150 fs͒ optical pulses. They exhibit the same main resonance frequency f and damping constant. However, a 90°phase shift was observed between linear and nonlinear responses proving that MOKE and MSHG oscillations are related to the temporal variations of different magnetization components M z and M y . Additionally, we found weak oscillations at the double frequency 2f. Comparing the results of static and dynamic MSHG measurements we evaluate the in-plane amplitude of the optically excited interfacial magnetization oscillations.