J. Grabis

Diffractometer for soft x-ray resonant magnetic scattering

We report on the design and construction of a new diffractometer for soft x-ray resonant magnetic scattering which has been built at the Ruhr-University Bochum. The ultrahigh vacuum-compatible diffractometer comprises a two-circle goniometer and works in horizontal scattering geometry. Rotation of the detector and sample is realized by two differentially pumped rotating platforms with motors and gears external to the vacuum. The sample environment consists of a closed-cycle He cryostat that allows heating up to 600 K and applying a magnetic field of ±2.5 kOe. All functions of the experimental setup have been extensively tested at the BESSY II Synchrotron (beamline PM3). The experimental results demonstrate the performance of the instrument.

X-ray resonant magnetic scattering study of [Co2MnGe/Au]n and [Co2MnGe/V]n multilayers

We study the structure and magnetism of the ferromagnetic half metallic Heusler compound Co2MnGe in high-quality [Co2MnGe/Au]n- and [Co2MnGe/V]n-multilayers by hard x-ray scattering and soft x-ray resonant magnetic scattering. The diffuse hard x-ray scattering reveals that in [Co2MnGe/Au]n at the interfaces correlated roughness dominates and interdiffusion is negligible, whereas in [Co2MnGe/V]n the roughness is uncorrelated and dominated by interdiffusion. An analysis of energy-dependent scans in the soft x-ray regime at the superlattice Bragg peaks allows a determination of the element-specific magnetic moment density profile within the Co2MnGe layers. We find that the magnetic moment density profile determined for Co and Mn is definitely different; moreover, it is narrower than the chemical density profile and asymmetric with respect to the growth direction. For [Co2MnGe/Au]n at room temperature a non-ferromagnetic interface layer exists with a thickness of about 0.6 nm at the bottom and 0.45 nm at the top of the Co2MnGe layers; for [Co2MnGe/V]n at the bottom and the top the corresponding thicknesses are 0.5 nm and 0.35 nm, respectively.

Energy shift of first excited state in 10Be

Using the reaction 9Be(d,p)10Be (Q = 4.59 MeV) at Ed = 1.0 MeV, the energy of the first excited state in 10Be was found to be 3368.34±0.43 keV, in excellent agreement with the literature value. The result strengthens conclusions derived from recent studies of the cold ternary spontaneous fission of 252Cf.

Magnetization Reversal Studies of Periodic Magnetic Arrays via Scattering Methods

Magnetic patterns with different shapes and aspect ratios provide control over the remanent domain state, the coercivity, and over different types of reversal mechanisms. We discuss magneto-optical, soft x-ray resonant scattering, and neutron scattering methods for evaluating the vector magnetization during reversal and the higher Fourier components of the magnetization distribution. These scattering methods, providing a statistical averaged signal, contrast real space methods, which give information on individual islands.

Heusler films and multilayers: X-ray resonant magnetic scattering and polarized neutron reflectivity studies on the relation between structure and magnetism

Abstract We have studied the structural properties and the magnetization density profiles in multilayers of the Heusler phase CoMnGe with three different spacer layers: V, Au, and AlO, using hard X-ray scattering, soft X-ray resonant magnetic scattering, and polarized neutron reflectivity. We have found that the spacer layer has a significant effect on the magnetization profile of the CoMnGe layer. In all cases the interlayers at the top and the bottom of the Heusler layer exhibit a reduced magnetic moment, the thickness of which depends on the spacer layer and increases from 0.5 nm for V, to 0.6 nm for Au and 1 nm for AlO.