J. C. Jousset

High-Energy Heavy-Ion Irradiations of Fe85B15 Amorphous Alloy: Evidence for Electronic Energy Loss Effect

Amorphous metallic Fe85B15 alloy has been irradiated at low temperature with Ar, Kr and Xe ions of initial energies of 1.8, 2.7 and 3.0 GeV, respectively. Electrical resistance was measured in situ on samples piled up along the beam direction. It is shown that above a given electronic stopping power threshold the electronic losses play a crucial role in radiation-induced damage.

Radiation Damage Induced by Electronic-Energy Loss in Amorphous Metallic Alloys

The electrical resistance of amorphous metallic Fe85B15 ribbons irradiated with 3 GeV Xe ions at different tilting angles with respect to the incident ion beam has been measured in situ at 77 K. The results show that irradiation induces large sample growth due to electronic-energy loss effects. The existence of a new mechanism leading to damage creation in metallic alloys by electronic excitation alone is also demonstrated.

Influence of the Electronic Stopping Power on the Damage Rate of Yttrium-Iron Garnets Irradiated by High-Energy Heavy Ions

Heavy-ion irradiation in the GeV range is an excellent way to investigate electronic stopping power effects in solids up to a few keV/A. Effects of 1.8 GeV Ar, 2.9 GeV Kr and 3.0 GeV Xe irradiations of yttrium-iron garnets have been investigated by magnetic measurements and transmission electronic microscopy (TEM). The dominant effect of electronic losses is demonstrated. For the first time, TEM images of latent tracks are presented.

Latent tracks induced by heavy ions in the GeV energy range: Results at GANIL

Abstract The specificity of swift heavy ions is related to the following facts: i) They have long ranges (> 100 μm for the ions produced at GANIL for instance); ii) over 90% of the ion range, the electronic stopping dominates entirely the elastic stopping, the ratio between the two being constant and of the order of 103; iii) The electronic stopping is very large (a few keV/A) and varies only slowly along the path. As a consequence, the swift heavy ions are ideally suited for the study of the damage induced by electronic losses in a thick target. But the most interesting feature is perhaps that the electronic stopping associated with very heavy ions is so high that highly nonlinear effects can occur, leading to structural phase transformation above a given electronic stopping power threshold (or, more precisely, above a given amount of the deposition energy density). The efficiency of heavy ions to induce damage was measured in different classes of materials: polymers, alkali-halides, silicates, magnetic insulators, organic conductors and also in metallic amorphous alloys.

Structural modifications induced by electronic energy deposition during the slowing down of heavy ions in matter

Abstract The defects or the phase transformations induced by high density electronic excitation are studied in thick targets. Two kinds of materials have been studied: electrical conductors and magnetic insulators. These materials are insensitive to individual electronic excitations such as those created by photon or electron irradiations. In amorphous metallic alloys a two step process of damage creation has been observed: defect production followed by a change of dimensions of the samples. In high-Tc. superconductors large electronic excitations enhance the rate of decrease of the critical temperature except in La2CuO4 where Tc increases upon ion irradiation. In the case of magnetic insulators a description of ion-induced tracks is proposed which accounts for the experimental data over the whole range of electronic energy losses. Two rates of damage, correlated with a change of the shape of induced defects, are shown by Mossbauer spectroscopy and high resolution electron microscopy observations.

Displacement threshold energy of iron atoms in amorphous and crystalline Fe75B25 alloys

Abstract Displacement threshold energy determination has been made at 21 K for amorphous a-Fe75B25 alloy and its crystalline c-Fe3B counterpart. The experiment consists in measuring the electrical resistivity increase rate during a 21-K electron irradiation as a function of the incident energy of the electron beam. The results can be summarized as follows: the displacement threshold energy is the same for both alloys (22±3)eV; the resistivity of an induced defect is (400±150) μΩ cm and (2700±700) μΩ cm for thea-Fe75B25 and c-Fe3B alloy respectively; with the help of 2.4 MeV production curves, the recombination volume has been evaluated for both alloys; at a given electron dose, the irradiation induced defects concentration is higher in the amorphous than in the crystalline alloy.

High energy heavy ion irradiation effects in yttrium iron garnet

The effects of heavy ion irradiation 1.8 GeV Ar and 2.9 GeV Kr in yttrium iron garnet have been investigated by means of electron diffraction, high resolution electron microscopy (HREM) and magnetization measurements. In the high energy zone (1.2 < E < 1.8 GeV for Ar ions and 2.1 < E < 2.9 GeV for Kr ions) a contrast of black and white stripes has been observed on HREM micrographs and assumed to be due to displacement cascade damage type. In the low energy zone (0 < E < 0.6 GeV for Ar ions and 0 < E < 0.9 GeV for Kr ions), a drastic change of the saturation magnetization has been observed and associated to a transition from a crystalline to amorphous state. The effect has been interpreted in term of atomic displacements rather than in term of tracks.

Electronic-energy-loss-assisted creep in heavy-ion-irradiated amorphous Fe85B15☆

Abstract The behaviour of amorphous metallic alloys submitted to swift heavy-ion irradiation is unusual and remarkable in several aspects. At low fluences electronic excitations modify the alloy short-range order; at higher fluences, huge plastic deformation occurs. This article reports the study of the influence of different uniaxial external stresses on the latter phenomenon, which can lead to a better understanding of the process. Electrical resistance measurements show that, contrarily to what was commonly expected, the externally applied stress induces a drastic additional plastic flow at 80 K.

Structural modifications of crystalline and amorphous Ni3B irradiated with high-energy heavy ions

Crystalline and amorphous Ni3B ribbons have been irradiated at low temperature with GeV heavy ions in order to study the structural modifications induced in metallic alloys by ion electronic energy loss. The atomic rearrangements produced by irradiation were characterized via in situ electrical resistance measurements and room-temperature X-ray and electron diffraction. Amorphous Ni3B behaves as the other amorphous alloys already investigated: creation of disorder with a cross section increasing with the ion electronic stopping power, followed by an anisotropic growth of the sample dimensions. Crystalline Ni3B shows a new and very interesting behavior: a huge electrical resistivity increase above an electronic energy loss threshold attributed to amorphization of the irradiated alloy.

Effects of electronic energy loss in crystalline and amorphous Ni3B irradiated with high-energy heavy ions

Abstract Crystalline Ni-B (c-Ni-B) and amorphous Ni-B (a-Ni-B) ribbons have been irradiated at 80 K with 3 GeV Xe ions in order to study the influence of the alloy structure on the disordering process induced by heavy-ion electronic energy loss. The relative electrical resistance variation of the samples measured in situ during irradiation reveals that the effect is much larger in the amorphous than in the crystalline system. The behaviour of a-Ni75B25 is basically that of a-Fe85B15: an increase in the alloy resistivity at the beginning of the irradiation, certainly due to disorder production, followed by a large growth of the sample dimensions. Both effects are attributed to electronic energy loss. On the contrary, c-Ni3B does not present any measurable growth; high-resolution electron microscopy experiments on single crystals indicate that, in the electronic stopping power range studied, the resistivity increase is essentially due to elastic collision events. A model has been derived to account for the ...