Structural and magnetic properties of CoO-Pt core-shell nanoparticles

Zeleňáková, Adriana; Zeleňák, Vladimir; Meisel, Mark W.; Kováč, Jozef; Michalík, Štefan

doi:10.1103/PhysRevB.89.104417

Journal Article

DESY-2014-02488

Structural and magnetic properties of CoO-Pt core-shell nanoparticles

Zeleňáková, A. (Corresponding Author)Extern* ; Zeleňák, V.Extern* ; Michalík, Š.Extern* ; Kováč, J. ; Meisel, M. W.

2014
APS College Park, Md.

Physical review / B 89(10), 104417 (2014) [10.1103/PhysRevB.89.104417]

This record in other databases:

Please use a persistent id in citations: doi:10.1103/PhysRevB.89.104417 doi:10.3204/DESY-2014-02488

Abstract: 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.

Classification: