Aggregation vs Surface Segregation: Antagonism over the Magnetic Behavior of NiCr Nanoparticles | Zendy

Murtaza Bohra | Zendy; Vidya Alman | Zendy; Arun Showry | Zendy; Vidyadhar Singh | Zendy; Rosa E. Diaz | Zendy; Mukhles Sowwan | Zendy; Panagiotis Grammatikopoulos | Zendy

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Aggregation vs Surface Segregation: Antagonism over the Magnetic Behavior of NiCr Nanoparticles

Author(s) -

Murtaza Bohra,

Vidya Alman,

Arun Showry,

Vidyadhar Singh,

Rosa E. Diaz,

Mukhles Sowwan,

Panagiotis Grammatikopoulos

Publication year - 2020

Publication title -

acs omega

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.779

H-Index - 40

ISSN - 2470-1343

DOI - 10.1021/acsomega.0c03056

Subject(s) - superparamagnetism , materials science , annealing (glass) , nanoparticle , spin glass , condensed matter physics , chemical physics , nichrome , magnetic nanoparticles , atom (system on chip) , nanotechnology , magnetism , magnetization , chemical engineering , magnetic field , metallurgy , chemistry , physics , quantum mechanics , computer science , engineering , embedded system

Annealing is a valuable method for fine-tuning the ultrasmall magnetic properties of alloy nanoparticles (NPs) by controlling their sizes, modifying their surfaces, and affecting their magnetic interactions. Herein, we study the effect of moderate annealing (450 °C) on strongly interacting NiCr nanoparticle assemblies (0 ≤ atom % Cr ≤ 15) immediately after deposition. Concurrent temperature-dependent electron microscopy and magnetization data demonstrate the interplay of two competing factors, namely, enhanced particle aggregation and element-specific surface segregation, on the magnetic properties, with the former boosting and the latter suppressing them. Strong interparticle interactions can lead to a magnetic response different from that of superparamagnetic particles, namely, from canonical spin-glass (0 atom % Cr) to correlated spin-glass (5-15 atom % Cr) behavior below higher spin-glass transition temperatures T g (20-350 K). The observation of " high-field susceptibility " below cryogenic temperatures (≤20 K) is ascribed to the presence of inhomogeneity/defects caused by Cr segregation. This work emphasizes the necessity of taking into account the delicate balance of such competing factors to understand the magnetic properties of nanoparticulate samples.

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