title: The remanence ratio in CoFe2O4nanoparticles with approximate single-domain sizes.
abstract: Approximately single-domain-sized 9-, 13-, and 16-nm CoFe2O4nanoparticles are synthesized using the thermal decomposition of a metal-organic salt. By means of dilution and reduction, the concentration, moment, and anisotropy of nanoparticles are changed and their influence on the magnetic properties is investigated. The relation of Mr/Ms∝ 1/lgHdipis observed, where Mr/Msis the remanence ratio and Hdipis the maximum dipolar field. Especially, such relation is more accurate for the nanoparticle systems with higher concentration and higher moment, i.e., larger Hdip. The deviation from Mr/Ms∝ 1/lgHdipappearing at low temperatures can be attributed to the effects of surface spins for the single-phase CoFe2O4nanoparticles and to the pinning effect of CoFe2O4on CoFe2for the slightly reduced nanoparticles. Graphical Abstract Approximately single-domain-sized 9-, 13-, and 16-nm CoFe2O4nanoparticles were synthesized and then the concentration, moment, and anisotropy of these NPs were changed. The correlation of Mr/Ms∝ 1/lgHdipwas observed, independent of the size, concentration, moment, and anisotropy, and especially, such correlation is more accurate for the nanoparticle systems with higher concentration or moment, i.e., stronger dipolar interaction, which has not been reported before as far as we know.
authors: Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science, Anhui University, Hefei, 230601, People's Republic of China.|School of Physics and Electronic Information, Huaibei Normal University, Huaibei, 235000, People's Republic of China.
authors: Shitao
authors: S
authors: Xu
authors: Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science, Anhui University, Hefei, 230601, People's Republic of China. yqma@ahu.edu.cn.
authors: Yongqing
authors: Y
authors: Ma
authors: Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science, Anhui University, Hefei, 230601, People's Republic of China.
authors: Bingqian
authors: B
authors: Geng
authors: Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science, Anhui University, Hefei, 230601, People's Republic of China.
authors: Xiao
authors: X
authors: Sun
authors: Anhui Key Laboratory of Information Materials and Devices, School of Physics and Materials Science, Anhui University, Hefei, 230601, People's Republic of China.
authors: Min
authors: M
authors: Wang
keywords: CoFe2O4 nanoparticles; Dipolar interaction; Remanence ratio; Surface spins