A. Gohla

TRANSIENT FIELD MEASUREMENT IN THE GIANT MOMENT PDFE ALLOY

Abstract The transient magnetic field (TF) for oxygen ions using the 16 O(3 − ) nuclear state as probe has been measured for the first time in the polycrystalline Pd 3 Fe ferromagnetic alloy. The measured value of the TF, associated with the polarized 1s-electron, has a strength B TF =169 (50) T corresponding to a degree of polarization of p 1s =0.058 (17). The results are in good agreement with calculations based on the spin exchange model. One concludes from these measurements, that the mean magnetization per host atom is responsible for the magnitude of the probes polarization.

Range and stopping power dependence of heavy ion-induced demagnetizations of ferromagnetic materials

Abstract Heavy ion beams induce by their stopping power severe demagnetizations of ferromagnetic materials of dynamic nature. This perturbation of ferromagnetism causes substantial attenuations of transient magnetic fields on traversing probe ions. A striking stopping power dependence has been found when the probe ions are in the H-like charge state. Due to the uncorrelated behaviour of beam ions and probe ions , moving on different trajectories through the ferromagnetic sample, the demagnetization, initially located at the ionization track of the beam ion, must propagate to the region of the probe ion. The determination of the range of demagnetization from its origin was the subject of the present measurements.

Preparation and analysis of targets with implanted thick Ar layers for in-beam γ-spectroscopy

Abstract Implantation of 80 keV 40 Ar ions into 0.5 mg/cm 2 thick Fe layers, deposited by vacuum evaporation onto a Gd foil, yielded an Ar target of 35(6) μg/cm 2 thickness which is suitable for in-beam γ-spectroscopy. Thin Fe-layer evaporation and implantation were successively applied in several cycles whereby the Ar implantation always occurred into a newly prepared Fe layer. These procedures can principally be extended for obtaining even larger thicknesses. The Ar content of the target and its layer thickness were accurately determined by the Elastic Recoil Detection Analysis technique using a 58 Ni beam.

Transient magnetic fields and electron polarizations of H-like oxygen ions in crystalline iron and amorphous iron-boron compounds

Abstract Transient magnetic fields (TF) have been measured for oxygen ions with the 16 O(3 − ) state as probe traversing thin layers of crystalline Fe and amorphous Fe 80 B 20 compounds. The TF associated with polarized 1s electrons have strengths of B TF (Fe) = 412 (38) T in Fe and B TF (FeB) = 368 (62) T in FeB implying degrees of polarization of p 1s (Fe) = 0.13 (1) and p 1s (FeB) = 0.14 (3), respectively. The strength parameter a = 12.1 (2.3) T deduced for FeB agrees very well with other data rendering it highly suitable for TF measurements.

AMORPHOUS FE TARGETS FOR TRANSIENT FIELD MEASUREMENTS WITH HEAVY-ION BEAMS

For transient field measurements (TF), ferromagnetic target foils of the amorphous Fe80 B20 compound were prepared with thicknesses between 2 and 8 μm. A minimum thickness of 8 μm was achieved employing a special lapping and polishing technique. For further thickness reduction, the ion-etching technique was used. Very promising results with respect to heavy-ion beam deterioration of TF were obtained in the preliminary measurements with this material.

Large transient magnetic fields of 28Si ions in backscattering through Fe at high velocities

Abstract Transient field (TF) precessions have been measured in Fe for high-velocity 28 Si ions following projectile Coulomb excitation of the first 2 + -state. In contrast to a recent measurement on 24 Mg ions which yielded at comparable velocity with the same geometry for the angular correlation an unexpected small TF, the present observations agree very well with the expectation of large TF: no diminution of the transferred polarization is found.

Transient field measurements with 80Se ions in glassy metals

Abstract Measurements of Transient Magnetic Fields (TF) were performed on 80 Se(2 + ) ions in amorphous Fe 80 B 20 alloys employing 48 Ti beams. The motivation was to study the influence of the amorphous structure of the host on the strength of TF, when the 2s-state of probe ions is responsible for the field. The results are compared with those of crystalline Fe, where large attenuations have been observed. The significantly smaller attenuation in the present conditions demonstrates the superiority of metallic glasses for g-factor measurements.

Evidence for ion beam induced attenuations of the static hyperfine field at recoil implanted 56Fe ions in Fe host

Abstract Measurements of transient (TF) and static (SF) magnetic hyperfine fields at 56 Fe(2 + ) ions, implanted in Fe host after Coulomb excitation using 16 O- and 56 Fe-beams, exhibit attenuations of the SF strength which is shown for the first time to be primarily due to the effect of the ion beam and only secondarily to that of the recoil ion. The beam induced attenuation is of the same nature and magnitude as for TF, which has been determined in former measurements. It must therefore arise from the depolarization of the Fe 3d electrons resulting from the ion stopping. The effect of the recoil implanted ion may be attributed to a thermal spike which seems to be more efficient for heavier probe ions.

Preparation and properties of segmented Fe targets for transient-field measurements

Abstract Multi-layered targets, consisting of segmented layers of Mg and ferromagnetic Fe on a thick Cu backing, have been prepared for transient-field experiments. The segmentation of 50 × 50 μ m squares or circles of 50 μm diameter was achieved applying the technique of photolithography and ion etching with Ar ions of 800 eV. The 10 μm thick Cu backing provided the mechanical support of the segmented structure.

New perspectives of transient field measurements using amorphous iron–boron compounds

Amorphous Fe–B alloys were used to determine transient magnetic fields (TF) for various probe ions. The aim of these investigations was to find out whether amorphous hosts are better suited under heavy ion beams, which generally cause in crystalline media very strong attenuations of TF. Experiments were performed with the light ions of 16O, 24Mg, 28Si as beams and probes to calibrate the TF. The attenuation behaviour was studied using heavy ion beams as 48Ti and 56Fe.