D. Labergerie

Hydrogen induced changes of the interlayer coupling in Fe(3)/V(x) superlattices (x=11–16)

Abstract The effect of hydrogen on the magnetic exchange coupling between iron layers through vanadium spacer layers has been studied with magneto-optical Kerr effect experiments in Fe (3) /V ( x ) superlattices. Here x refers to the number of V monolayers varying from 11 to 16 and the Fe layer thickness is fixed at three monolayers. Without hydrogen the superlattice is antiferromagnetic (AFM) for x between 12 and 14 and ferromagnetic (FM) in all other cases. With hydrogen loading the coupling can be switched from AFM to FM and vice versa. As previously observed with neutron reflectivity measurements (Hjorvarsson et al., Phys. Rev. Lett. 79 (1997) 901) the change of the interlayer coupling upon hydrogen uptake is not simply due to the expansion of the non-magnetic vanadium spacer layer but more likely to the distortion of the Fermi surface. Bilinear and biquadratic exchange couplings can be recognized by the magnetic hysteresis loops and their coupling energies have been extracted by fits to the curves. For all samples the easy axis of the magnetization is in the plane without any preferred in-plane direction. Hydrogen loading does not affect the magnetic anisotropy of these samples.

Evolution of atomic magnetic moments in Fe/V multilayers with hydrogen loading

Abstract The change of the magnetic saturation magnetisation of Fe/V superlattices upon in situ loading with hydrogen was investigated using a highly sensitive Faraday balance. Without hydrogen the magnetic moments in the superlattice were found to be considerably smaller than those obtained by ab initio calculations, whereas the moment increase with hydrogen was notably larger than predicted by ab initio calculations. Calculations of the Fe/V and Fe/V–H superlattices with intermixing at the interface were performed within the periodic Anderson model. They demonstrate the key role of interface alloying for the formation of magnetic properties.

Hydrogen in thin epitaxial metal films and superlattices: structure, magnetism, and transport

Abstract Hydrogen in thin epitaxial films and superlattices has gained renewed interest because of the hydrogen-induced novel optical and magnetic switching properties that have recently been unraveled. In this contribution we present new results on the effect of hydrogen on the structural properties of epitaxial Y-films and the H–D isotope exchange in the trihydride phase. We also report on magneto-optical Kerr effect measurements of the magnetic hysteresis in Fe (3) /V ( x ) superlattices as a function of the hydrogen pressure. Here x refers to the number of V monolayers varying from 11 to 16 and the Fe layer thickness fixed at three monolayers. Without hydrogen the superlattice is antiferromagnetic (AFM) for x between 12 and 14 and ferromagnetic (FM) in all other cases. With hydrogen loading the coupling can be switched from AFM to FM and vice versa.

On the structure of epitaxial YHx films

Hydrogen in thin epitaxial films and superlattices has gained renewed interest because of the hydrogen-induced novel optical and magnetic switching properties that have recently been revealed. In this contribution we report on structural details on the effect of hydrogen in epitaxial Y-films. X-ray diffraction reveals the response of the host metal lattice upon hydrogen loading. The hydrogen ordering within the hydride phases as well as the hydrogen concentration can be measured by neutron diffraction. The macroscopic aspects of the hydride formation like domain nucleation and growth are accessible by in-situ real time X-ray diffraction topography.

Hydrogen in thin epitaxial Nb films

Abstract The solubility isotherms of hydrogen in epitaxial Nb(100) films have been determined via in situ X-ray lattice-parameter measurements. The Nb films were grown by molecular-beam epitaxial techniques on R-Al 2 O 3 substrates with different thicknesses varying from 34 to 204 nm. Similar to Nb(110) films, the maximum out-of-plane lattice expansion scales inversely with Nb(100) film thickness. Furthermore, the critical temperature T c for the α-α′ phase transition as derived from the solubility isotherms depends strongly on the film thickness. For both orientations we determine similar T c ’s but for film thicknesses below 30 nm, T c in Nb(100) films are higher by about 80 K as compared to Nb(110) films. The influence of finite size scaling and adhesion of the films to the substrates on the solubility isotherms will be discussed.