Magnetic anisotropy and reversal in epitaxial Fe/MgO(001) films revisited

We investigate the magnetization reversal in Fe/MgO(001) films with fourfold in-plane magnetic anisotropy and an additional uniaxial anisotropy whose orientation and strength are tuned using different growth geometries and post growth treatments. The previously adopted mechanism of 180^{o} domain wall nucleation clearly fails to explain the observed 180^{o} magnetization reversal. A new reversal mechanism with two successive domain wall nucleations consistently predicts the switching fields for all field orientations. Our results are relevant for a correct interpretation of magnetization reversal in many other epitaxial metallic and semiconducting thin films.Comment: 4 pages, 4 figure

Reversing the training effect in exchange biased CoO/Co bilayers

We performed a detailed study of the training effect in exchange biased CoO/Co bilayers. High-resolution measurements of the anisotropic magnetoresistance (AMR) are consistent with nucleation of magnetic domains in the antiferromagnetic CoO layer during the first magnetization reversal. This accounts for the enhanced spin rotation observed in the ferromagnetic Co layer for all subsequent reversals. Surprisingly, the AMR measurements as well as magnetization measurements reveal that it is possible to partially reinduce the untrained state by performing a hysteresis measurement with an in plane external field perpendicular to the cooling field. Indeed, the next hysteresis loop obtained in a field parallel to the cooling field resembles the initial asymmetric hysteresis loop, but with a reduced amount of spin rotation occurring at the first coercive field. This implies that the antiferromagnetic domains, which are created during the first reversal after cooling, can be partially erased.Comment: 4 pages, 4 figure

Surface morphology and magnetic anisotropy of Fe/MgO(001) films deposited at oblique incidence

We have studied surface morphology and magnetic properties of Fe/MgO(001) films deposited at an angle varying between 0o and 60o with respect to the surface normal and with azimuth along the Fe[010] or the Fe[110] direction. Due to shadowing, elongated grains appear on the film surface for deposition at sufficiently large angle. X-ray reflectivity reveals that, depending on the azimuthal direction, films become either rougher or smoother for oblique deposition. For deposition along Fe[010] the pronounced uniaxial magnetic anisotropy (UMA) results in the occurrence of reversed two-step and of three-step hysteresis loops. For deposition along Fe[110] the growth-induced UMA is much weaker, causing a small rotation of the easy axes.Comment: 3 pages, 4 figure

M & L Jaargang 22/5

Chris De Maegd Het kasteeldomein van Heers: een boeiend monument. [An intriguing monument: the demesne of Heers.]Jo Braeken Schoonheid van Dynamo en Sunbeam. De luchthaven van Deurne, een vergeten pionier. [Beauty of Dynamo and Sunbeam. The airport of Deurne. Forgotten pioneer.]Alain de Winiwarter Een techniek van derestauratie. Toepassing op twee barokke biechtstoelen van de kerk Saint-Loup in Namen. [A technique of derestoration. The application on two baroque confessionals in the Saint Loup church in Namur.]Rob Buelens en Chris Van Haesendonck Een beveiligde expositieruimte voor de zilvercollectie van de Onze-Lieve-Vrouwekerk te Aarschot. [A treasure-chamber within a monument. A permanent exposition room for the silver treasure of Our Ladys collegiate church in Aarschot.]Summar

Thin film growth of semiconducting Mg2Si by codeposition

Includes bibliographical references (page 1088).Ultrahigh vacuum evaporation of magnesium onto a hot silicon substrate (⩾200 °C), with the intention of forming a Mg2Si thin film by reaction, does not result in any accumulation of magnesium or its silicide. On the other hand, codeposition of magnesium with silicon at 200 °C, using a magnesium-rich flux ratio, gives a stoichiometric Mg2Si film which can be grown several hundreds of nm thick. The number of magnesium atoms which condense is equal to twice the number of silicon atoms which were deposited; all the silicon condenses while the excess magnesium in the flux desorbs. The Mg2Si layers thus obtained are polycrystalline with a (111) texture. From the surface roughness analysis, a self-affine growth mode with a roughness exponent equal to 1 is deduced

M & L Jaargang 22/5

Summar

Spontaneous doping of two-dimensional NaCl films with Cr atoms: aggregation and electronic structure

Upon deposition of Cr atoms on ultrathin NaCl/Au(111) films they form substituting dopants either replacing Na or Cl ions, thereby changing the electronic properties of the film and in particular the work function

Deposition of toxic metal particles on rough nanofiltration membranes

Two nanofiltration (NF90 and Nano-Pro-3012) membranes were investigated for their capacity to remove metal ions. This study presents the effect of membrane roughness on the removal of toxic metal ions during dead end membrane filtration. Atomic force microscopy, scanning electron microscopy, WSXM software and ImageJ were used to characterize the roughness of the membranes. Gradual decrease in filtration permeate flux was observed as foulants accumulated at the interface of the membranes; filtration permeate flux varied from 20 L/m2/h to 14 L/m2/h and 11 L/ m2/h to 6 L/m2/h for NF90 and Nano-Pro-3012, respectively. NF90 membrane was more prone to fouling than the Nano- Pro-3012 membrane: the percentage flux reduction was higher for NF90 (3.6%) than Nano-Pro-3012 (0.98%). The bearing ratio of the fouled NF90 exhibited a high peak of 7.09 nm than the fouled Nano-Pro-3012 with the peak of 6.8 n

Spin excitations of individual magnetic dopants in an ionic thin film

Individual magnetic transition metal dopants in a solid host usually exhibit relatively small spin excitation energies of a few meV. Using scanning tunneling microscopy and inelastic electron tunneling spectroscopy (IETS) techniques, we have observed a high spin excitation energy around 36 meV for an individual Co substitutional dopant in ultrathin NaCl films. In contrast, the Cr dopant in the NaCl film shows much lower spin excitation energy around 2.5 meV. Electronic multiplet calculations combined with first-principles calculations confirm the spin excitation induced IETS, and quantitatively reveal the out-of-plane magnetic anisotropies for both Co and Cr. They also allow reproducing the experimentally observed redshift in the spin excitations of Co dimers and ascribe it to a charge and geometry redistribution.This research was supported by the National Natural Science Foundation of China (91961102, 11704057), the Shenzhen fundamental research funding (JCYJ20190806112206698), the starting funding from HIT Shenzhen (HA45001082), and the Research Foundation Flanders (G0D56.19N and G0A05.19N) and by the KU Leuven Research Council (C14/22/103). Financial support by the following Projects: RTI2018-097895-B-C41, PID2019-109539GB-C41 and PID2019-103910GB-I00, funded by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa, as well as GIU18/138 by Universidad del Pais Vasco UPV/EHU; IT-1246-19, IT986-16 and IT-1260-19 by Gobierno Vasco, is gratefully acknowledged