Controlling orbital moment and spin orientation in CoO layers by strain

We have observed that CoO films grown on different substrates show dramatic differences in their magnetic properties. Using polarization dependent x-ray absorption spectroscopy at the Co L$_{2,3}$ edges, we revealed that the magnitude and orientation of the magnetic moments strongly depend on the strain in the films induced by the substrate. We presented a quantitative model to explain how strain together with the spin-orbit interaction determine the 3d orbital occupation, the magnetic anisotropy, as well as the spin and orbital contributions to the magnetic moments. Control over the sign and direction of the strain may therefore open new opportunities for applications in the field of exchange bias in multilayered magnetic films

Magnetic versus crystal field linear dichroism in NiO thin films

We have detected strong dichroism in the Ni $L_{2,3}$ x-ray absorption spectra of monolayer NiO films. The dichroic signal appears to be very similar to the magnetic linear dichroism observed for thicker antiferromagnetic NiO films. A detailed experimental and theoretical analysis reveals, however, that the dichroism is caused by crystal field effects in the monolayer films, which is a non trivial effect because the high spin Ni $3d^{8}$ ground state is not split by low symmetry crystal fields. We present a practical experimental method for identifying the independent magnetic and crystal field contributions to the linear dichroic signal in spectra of NiO films with arbitrary thicknesses and lattice strains. Our findings are also directly relevant for high spin $3d^{5}$ and $3d^{3}$ systems such as LaFeO$_{3}$, Fe$_{2}$O$_{3}$, VO, LaCrO$_{3}$, Cr$_{2}$O$_{3}$, and Mn$^{4+}$ manganate thin films

Human papillomavirus type 18 infection in a female renal allograft recipient : a case report

Publisher Copyright: © 2016 The Author(s).Background: Human papillomavirus type 18 is the second most common cause of cervical cancer and is found in 7 to 20 % of cases of cervical cancer. The oncogenic potential of high-risk human papillomavirus is associated with expression of early proteins E6 and E7. Due to long-term immunosuppressive therapy, renal transplant recipients have a higher risk of developing persistent human papillomavirus infection. Case presentation: A 29-year-old white woman from Latvia with chronic focal segmental glomerulosclerosis received renal allograft transplantation and was prescribed immunosuppressive therapy with cyclosporine, prednisolone, and mycophenolate mofetil. Two weeks after renal transplantation, her cervical swab was positive for human papillomavirus consensus sequences. After 6 months, quantitative polymerase chain reaction showed a high viral load of 3,630,789 copies/105 cells of high-risk human papillomavirus type 18 and expression of E6 and E7 oncogenes in her cervical swab and urine sample. One year after renal transplantation, the viral load in her cervical swab increased significantly to 7,413,102 copies/105 cells. Messenger ribonucleic acid of human papillomavirus type 18 E6 and E7 oncogenes were also detected. Shortly after this, she had an unsuccessful pregnancy which resulted in a spontaneous abortion at 6/7 weeks. Two months after the abortion her viral load sharply decreased to 39 copies/105 cells. Oncogenes E6 and E7 messenger ribonucleic acid expression was not observed in this period. Conclusions: This case report represents data which show that immunosuppressive therapy may increase the risk of developing persistent high-risk human papillomavirus infection with expression of E6 and E7 oncogenes in renal transplant recipients. However, even during this therapy the immune status of a recipient can improve and contribute to human papillomavirus viral load reduction. Spontaneous abortion can be considered a possible contributory factor in human papillomavirus clearance.publishersversionPeer reviewe

Growth and properties of strained VOx thin films with controlled stoichiometry

We have succeeded in growing epitaxial films of rocksalt VOx on MgO(001) substrates. The oxygen content as a function of oxygen flux was determined using 18O2-RBS and the vanadium valence using XAS. The upper and lower stoichiometry limits found are similar to the ones known for bulk material (0.8<x<1.3). From the RHEED oscillation period a large number of vacancies for both vanadium and oxygen were deduced, i.e. ~16% for stoichiometric VO. These numbers are, surprisingly, very similar to those for bulk material and consequently quite strain-insensitive. XAS measurements reveal that the vacancies give rise to strong low symmetry ligand fields to be present. The electrical conductivity of the films is much lower than the conductivity of bulk samples which we attribute to a decrease in the direct overlap between t2g orbitals in the coherently strained layers. The temperature dependence of the conductivity is consistent with a variable range hopping mechanism.Comment: 12 pages, 16 figures included, revised versio

X-rays diffraction on a new chromium oxide single-crystal thin film prepared by molecular beam epitaxy

Chromium oxide films were prepared on MgO substrates by molecular beam epitaxy. The crystalline structure of the films was characterized by X-ray diffraction (XRD) with conventional as well as synchrotron X-ray sources. The theta-2 theta spectra showed that the film was a new chromium oxide epitaxially grown on MgO(00 1) substrate. The structure of the film was revealed to be body-centred orthorhombic both by reciprocal space mapping and synchrotron Q scans. The unit cell parameters were determined to be a = 8.94, b = 2.98 and c = 3.892 angstrom. The film had a 45 degrees in-plane orientation with respect to MgO substrate. The crystalline structure of the films was equivalent to a NaCl-type CrO with 1/3 Cr atoms vacating along MgO direction in an ordered way. (c) 2006 Elsevier B.V. All rights reserved