Uncompensated Magnetic Moment and Surface and Size Effects in Few-Nanometer Antiferromagnetic NiO Particles | Sciact - CRIS-system of Boreskov Institute of Catalysis

Uncompensated Magnetic Moment and Surface and Size Effects in Few-Nanometer Antiferromagnetic NiO Particles Full article

Journal

Journal of Magnetism and Magnetic Materials
ISSN: 0304-8853

Output data

Year: 2021, Volume: 539, Article number : 168343, Pages count : 9 DOI: 10.1016/j.jmmm.2021.168343

Tags

Antiferromagnetic NiO nanoparticles; Superparamagnetism; Surface magnetic anisotropy; Uncompensated magnetic moment

Authors

Balaev D.A. ^1,2 , Krasikov A.A. ¹ , Popkov S.I. ¹ , Semenov S.V. ^1,2 , Volochaev M.N. ¹ , Velikanov D.A. ¹ , Kirillov V.L. ³ , Martyanov O.N. ³

Affiliations

1	Kirensky Institute of Physics, Federal Research Center “Krasnoyarsk Scientific Center”, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia
2	Siberian Federal University, Krasnoyarsk 660041, Russia
3	Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia

The analysis of the M(H) magnetization curves of antiferromagnetic nanoparticles yields information about magnetic subsystems formed in these objects, which are characterized by a large fraction of surface atoms. However, in the conventionally investigated experimental magnetic field range of up to 60–90 kOe, this analysis often faces the ambiguity of distinguishing the Langevin function-simulated contribution of uncompensated magnetic moments μun of particles against the background of a linear-in-field dependence (the antiferromagnetic susceptibility and other contributions). Here, this problem has been solved using a pulsed technique, which makes it possible to significantly broaden the range of external fields in which the μun contribution approaches the saturation. Nanoparticles of a typical NiO antiferromagnet with an average size of <d> ~ 4.5 nm have been investigated. Based on the thorough examination of the M(H) magnetization curves measured in pulsed fields of up to 250 kOe, a model of the magnetic state of NiO nanoparticles of such a small size has been proposed. The average moment is ~130 μB (μB is the Bohr magneton) per particle, which corresponds to 60–70 decompensated spins of nickel atoms localized, according to the Néel hypothesis (μun ~ <d>3/2), both on the surface and in the bulk of a particle. A part of the surface spins unrelated to the antiferromagnetic core form another subsystem, which behaves as free paramagnetic atoms. Along with the antiferromagnetic core, an additional linear-in-field contribution has been detected, which is apparently related to superantiferromagnetism, i.e., the size effect inherent to small antiferromagnetic particles.

Balaev D.A. , Krasikov A.A. , Popkov S.I. , Semenov S.V. , Volochaev M.N. , Velikanov D.A. , Kirillov V.L. , Martyanov O.N.
Uncompensated Magnetic Moment and Surface and Size Effects in Few-Nanometer Antiferromagnetic NiO Particles
Journal of Magnetism and Magnetic Materials. 2021. V.539. 168343 :1-9. DOI: 10.1016/j.jmmm.2021.168343 WOS Scopus РИНЦ AN OpenAlex

Submitted:	Dec 17, 2020
Accepted:	Jul 23, 2021
Published online:	Jul 28, 2021
Published print:	Dec 1, 2021

Web of science:	WOS:000705170900004
Scopus:	2-s2.0-85112594156
Elibrary:	47027596
Chemical Abstracts:	2021:1752056
OpenAlex:	W3186658864

DB	Citing
Scopus	20
Elibrary	22
Web of science	19
OpenAlex	23