Competing magnetic states and M- H loop splitting in core-shell NiO nanoparticles

Hur Abbas; K Nadeem; J Hester; M F Pervez; S Yick; M Kostylev; Ilse Letofsky-Papst; B Ali; C Ulrich; H Krenn

doi:10.1088/1361-6528/ac6dc3

Competing magnetic states and M- H loop splitting in core-shell NiO nanoparticles

Nanotechnology. 2022 Jun 7;33(34). doi: 10.1088/1361-6528/ac6dc3.

Authors

Hur Abbas¹, K Nadeem¹, J Hester², M F Pervez³, S Yick^{2

3}, M Kostylev⁴, Ilse Letofsky-Papst⁵, B Ali¹, C Ulrich³, H Krenn⁶

Affiliations

¹ Nanoscience and Technology Laboratory, Department of Physics, International Islamic University, Islamabad 44000, Pakistan.
² Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights NSW 2234, Australia.
³ School of Physics, The University of New South Wales, Kensington NSW 2052, Australia.
⁴ School of Physics, The University of Western Australia, Crawley, WA 6009, Australia.
⁵ Institute of Electron Microscopy, University of Technology Graz, Steyrergasse 17, A-8010 Graz, Austria.
⁶ Institute of Physics, Karl-Franzens University, Universitätsplatz 5, A-8010 Graz, Austria.

PMID: 35525188
DOI: 10.1088/1361-6528/ac6dc3

Abstract

Magnetic relaxation in a nanoparticles system depends on the intra-particle interactions, reversal mechanism, the anisotropy field, easy axis distribution, particle volume, lattice defects, surface defects, materials composite, etc. Here we report the competing magnetic states between superparamagnetic blocking and Néel transition states in 14 nm core-shell NiO nanoparticles. A crossover temperature of 50 K was observed for both these states from the zero field cooled/field cooled magnetization curves taken at different fields. At crossover temperature, an interestingM-Hloop splitting is observed which is attributed to the slow spin relaxation. This anomalousM-Hloop splitting behaviour was found to be particle size dependent and suppressed for diameters above and below 14 nm which indicates a critical size for these competing magnetic states. Additional neutron diffraction experiments confirmed this observation. This experimental study provides a new insight for the understanding of intra-particle interactions in fine antiferromagnetic nanoparticles and obtained results are an important step towards deeper understanding of the competing/non-competing modes between superparamagnetic blocked and Néel transition states.

Keywords: core–shell nanoparticles; magnetic interactions; neutron diffraction.