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Neutron scattering experiments using a two-dimensional detector have been performed to measure simultaneously a nuclear Bragg peak and its six surrounding magnetic satellites in a 2 μm thick (110)europium film. This technique enables the investigation of the three helical orders propagating along different directions, which gives a complete information on the magnetic configuration at a given temperature. Important variations in temperature and hysteretic effects have been observed for the magnetic population, in good agreement with a previous structural analysis. The thermal history of the film appears also to have dramatic consequences on the magnetic configurations, correlated with lattice clamping effects persisting above the magnetic ordering temperature. [ABSTRACT FROM AUTHOR]

Below its ordering temperature ( T N = 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010]. This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate direction, specifically [ $$ \bar 1 $$ 10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors. Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not vary under magnetic field. [ABSTRACT FROM AUTHOR]

A detailed structural analysis of the epitaxial growth of europium using in situ reflection high-energy electron diffraction has been performed for two kinds of buffer layers with different symmetry: (1 1 0)niobium (Nb) and (0 0 0 1)yttrium (Y). Moreover, by varying the preparation conditions of the (1 1 0)Nb layer we get either a reconstructed or an unreconstructed Nb surface, which turns out to have a strong influence on the Eu growth: the reconstructed (1 1 0)Nb surface favours the stabilisation of an Eu hexagonal surface structure, as well as the (0 0 0 1)Y buffer, whereas a pure unreconstructed (1 1 0)Nb surface enables the growth of single crystalline bcc (1 1 0)Eu films. With increasing Eu thickness, the relaxation of the metastable Eu hexagonal surface obtained on (0 0 0 1)Y or on reconstructed (1 1 0)Nb gives rise to a multidomain structure that drastically depends on the nature of the underlying buffer layer. [Copyright &y& Elsevier]

In-plane and out-ot-plane lattice parameters of Nb and Eu have been measured as a function of temperature between 10 and 300 K in the Al2O3(11&2macr;0)/Nb(110)/Eu(110) epitaxial system. It is shown that the Nb lattice is clamped in the growth plane to the sapphire substrate, in the whole temperature range. On its own, the Eu lattice is totally free to expand isotropically above a clamping temperature Tcl, below which in-plane parameters also freeze to an almost constant value. This well-defined clamping temperature strongly depends on the Eu thickness and likely is related to the thermal mobility of interface defects. [ABSTRACT FROM AUTHOR]

Abstract: Single crystal Eu(110) films exhibit an atypical magnetic arrangement, different from the bulk three helices configuration: at low temperature, under zero field, only two magnetic domains are present since the magnetic helix that propagates along the in-plane [001] axis disappears below a given temperature. This paper presents the study of the stability of the magnetic domains under magnetic field using neutron scattering experiments and magnetisation measurements on a 375nm thick Eu(110) film. The helix propagating along [001] is restored by the application of an external field along the [001] direction, which gives rise to a supplemental Zeeman contribution. [Copyright &y& Elsevier]