23 research outputs found
On Using Magnetic and optical methods to determine the size and characteristics of nanoparticles embedded in oxide semiconductors
Films of oxides doped with transition metals are frequently believed to have
magnetic inclusions. Magnetic methods to determine the amount of nanophases and
their magnetic characteristics are described. The amount of the sample that is
paramagnetic may also be measured. Optical methods are described and shown to
be very powerful to determine which defects are also magnetic.Comment: Manuscript of poster to be presented at MMM-Intermag 2010. Accepted
for publication in Magnetic Trans of IEE
Magneto-optical properties of Co/ZnO multilayer films
Multilayer films of ZnO with Co were deposited on glass substrates then
annealed in a vacuum. The magnetisation of the films increased with annealing
but not the magnitude of the magneto-optical signals. The dielectric functions
for the films were calculated using the MCD spectra. A Maxwell Garnett theory
of a metallic Co/ZnO mixture is presented. The extent to which this explains
the MCD spectra taken on the films is discussed.Comment: This paper was presented at ICM (2009) and is accepted in this form
for the proceeding
Spin polarized transport current in n-type co-doped ZnO thin films measured by Andreev spectroscopy
We use point contact Andreev reflection measurements to determine the spin
polarization of the transport current in pulse laser deposited thin films of
ZnO with 1% Al and with and without 2%Mn. Only films with Mn are ferromagnetic
and show spin polarization of the transport current of up to 55 0.5% at
4.2 K, in sharp contrast to measurements of the nonmagnetic films without Mn
where the polarization is consistent with zero. Our results imply strongly that
ferromagnetism in these Al doped ZnO films requires the presence of Mn.Comment: Published versio
Enhanced magnetic properties in ZnCoAlO caused by exchangecoupling to Co nanoparticles
We report the results of a sequence of magnetisation and magneto-optical studies on laser ablated thin films of ZnCoAlO and ZnCoO that contain a small amount of metallic cobalt. The results are compared to those expected when all the magnetization is due to isolated metallic clusters of cobalt and with an oxide sample that is almost free from metallic inclusions. Using a variety of direct magnetic measurements and also magnetic circular dichroism we find that there is ferromagnetism within both the oxide and the metallic inclusions, and furthermore that these magnetic components are exchange-coupled when aluminium is included. This enhances both the coercive field and the remanence. Hence the presence of a controlled quantity of metallic nanoparticles in ZnAlO can improve the magnetic response of the oxide, thus giving great advantages for applications in spintronics
Letter. Inactivating mutations of the histone methyltransferase gene EZH2 in myeloid disorders
Abnormalities of chromosome 7q are common in myeloid malignancies, but no specific target genes have yet been identified. Here, we describe the finding of homozygous EZH2 mutations in 9 of 12 individuals with 7q acquired uniparental disomy. Screening of a total of 614 individuals with myeloid disorders revealed 49 monoallelic or biallelic EZH2 mutations in 42 individuals; the mutations were found most commonly in those with myelodysplastic/myeloproliferative neoplasms (27 out of 219 individuals, or 12%) and in those with myelofibrosis (4 out of 30 individuals, or 13%).EZH2 encodes the catalytic subunit of the polycomb repressive complex 2 (PRC2), a highly conserved histone H3 lysine 27 (H3K27) methyltransferase that influences stem cell renewal by epigenetic repression of genes involved in cell fate decisions. EZH2 has oncogenic activity, and its overexpression has previously been causally linked to differentiation blocks in epithelial tumors. Notably, the mutations we identified resulted in premature chain termination or direct abrogation of histone methyltransferase activity, suggesting that EZH2 acts as a tumor suppressor for myeloid malignancies.<br/