TY  - JOUR
AU  - Zeleňáková, Adriana
AU  - Zeleňák, Vladimir
AU  - Michalík, Štefan
AU  - Kováč, Jozef
AU  - Meisel, Mark W.
TI  - Structural and magnetic properties of CoO-Pt core-shell nanoparticles
JO  - Physical review / B
VL  - 89
IS  - 10
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - DESY-2014-02488
SP  - 104417
PY  - 2014
AB  - Using microemulsion methods, CoO-Pt core-shell nanoparticles, with diameters of nominally 4 nm, weresynthesized and characterized by high-resolution transmission electron microscopy and a suite of x-rayspectroscopies, including diffraction, absorption, absorption near-edge structure, and extended absorption finestructure, which confirmed the existence of CoO cores and pure Pt surface layers. Using a commercialmagnetometer, the ac and dc magnetic properties were investigated over a range of temperature (2 K <  T < 300 K), magnetic field (< 50 kOe), and frequency (< 1 kHz). The data indicate the presence of two differentmagnetic regimes whose onsets are identified by two maxima in the magnetic signals, with a narrow maximumcentered at 6 K and a large one centered at 37 K. The magnetic responses in these two regimes exhibit differentfrequency dependencies, where the maximum at high temperature follows a Vogel-Fulcher law, indicating asuperparamagnetic blocking of interacting nanoparticle moments and the maximum at low temperature possessesa power-law response characteristic of a collective freezing of the nanoparticle moments in a superspin glassstate. This co-existence of blocking and freezing behaviors is consistent with the nanoparticles possessing anantiferromagnetically ordered core, with an uncompensated magnetic moment, and a magnetically disorderedinterlayer between the CoO core and the Pt shell.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000333125100003
DO  - DOI:10.1103/PhysRevB.89.104417
UR  - https://bib-pubdb1.desy.de/record/168323
ER  -