Showing papers by "Markus Münzenberg published in 1998"

Ion-beam induced magnetic anisotropies in iron films

Abstract: 100–300 nm thin Fe layers evaporated onto crystalline and amorphous Si or SiO2 substrates were irradiated, at 77 K, with 1014–1016 Xe+-ions/cm2 at 450 keV beam energy. The magnetizations in the films were measured by means of Perturbed Angular Correlation (PAC) spectroscopy with implanted 111In tracer ions, or the Magneto-Optic Kerr Effect (MOKE). Upon ion implantation, dramatic changes of the magnetic anisotropy were observed which are attributed to ion-beam enhanced lateral grain growth. Very little influence of the deposition parameters (type and cristallinity of substrate, evaporation rate) on the anisotropic magnetization was found.

4f and 5d magnetic moments in highly correlated [Ce/La/Fe] and [La/Ce/Fe] multilayers studied by x-ray magnetic circular dichroism

Abstract: Experiments are reported of x-ray absorption and x-ray magnetic circular dichroism at the ${L}_{2,3}(2\stackrel{\ensuremath{\rightarrow}}{p}5d)$ and ${M}_{4,5}(3\stackrel{\ensuremath{\rightarrow}}{d}4f)$ absorption edges of Ce and La in the multilayers [La/Ce(10\AA{})/La/Fe(30\AA{})]$\ifmmode\times\else\texttimes\fi{}n$ and [Ce/La(10\AA{})/Ce/Fe(30\AA{})]$\ifmmode\times\else\texttimes\fi{}n$. In these layers, Ce adopts an $\ensuremath{\alpha}$-phase-like electronic structure. Strong $3d\ensuremath{-}5d$ and $3d\ensuremath{-}4f$ hybridization is effective at the interfaces. It induces an ordered magnetic moment on the $5d$ and $4f$ states in the ground state of Ce and of the $5d$ states of La at room temperature, in antiparallel orientation to the Fe moment. By choosing the special laminar structure of the two lanthanides intercalated in between the Fe layers, the spatial extension of the Fe-induced magnetic order is directly probed. The $4f$ polarization of Ce and the $5d$ polarization of La are limited to the direct interface with Fe. In contrast, the polarization of Ce-$5d$ states extends deeply into the layers. There is evidence that the $5d$ states of $\ensuremath{\alpha}$-like Ce in these layered structures are very close to a ferromagnetic instability. Remarkably, magnetic order on the Ce-$5d$ states can exist without a polarization of the $4f$ states. Apparently the $4f\ensuremath{-}(5d,6s)$ hybridization wins over the intraatomic $4f\ensuremath{-}5d$ exchange interaction, and stabilizes a nonmagnetic $4f$ ground state. Comparative studies on alloys Ce${}_{x}$Fe${}_{1\ensuremath{-}x}$ confirm this observation: near $x=0.34$ the polarization of the $4f$ states gets lost, but the $5d$ states are magnetically ordered. The special electronic and magnetic properties of Ce and La in the multilayer systems are reflected in the reversal of the macroscopic magnetization studied by the magneto-optical Kerr effect.

Imprinting magnetic structures

Abstract: We created helical magnetic structures by depositing in sequence layers of lanthanum and iron (each 30 A thick) on a substrate rotating in a fixed field of a few Oe The magnetic field was sufficient to define the magnetization of each layer during growth without disturbing the magnetization of the layers already formed As a result, the imprinted helical magnetic structure had a chirality given by the direction of rotation of the substrate; the pitch was given by the speed of rotation and the rate of deposition This finding indicates that it is possible to engineer mesoscopic magnetic structures