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

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

doi:10.1021/acsomega.0c03056

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

Murtaza Bohra^*, Vidya Alman, Arun Showry, Vidyadhar Singh, Rosa E. Diaz, Mukhles Sowwan, Panagiotis Grammatikopoulos^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

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 Tg (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.

Original language	English
Pages (from-to)	32883-32889
Number of pages	7
Journal	ACS Omega
Volume	5
Issue number	51
DOIs	https://doi.org/10.1021/acsomega.0c03056
State	Published - 29 Dec 2020
Externally published	Yes

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title = "Aggregation vs Surface Segregation: Antagonism over the Magnetic Behavior of NiCr Nanoparticles",

abstract = "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 Tg (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.",

author = "Murtaza Bohra and Vidya Alman and Arun Showry and Vidyadhar Singh and Diaz, {Rosa E.} and Mukhles Sowwan and Panagiotis Grammatikopoulos",

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doi = "10.1021/acsomega.0c03056",

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T1 - Aggregation vs Surface Segregation

T2 - Antagonism over the Magnetic Behavior of NiCr Nanoparticles

AU - Bohra, Murtaza

AU - Alman, Vidya

AU - Showry, Arun

AU - Singh, Vidyadhar

AU - Diaz, Rosa E.

AU - Sowwan, Mukhles

AU - Grammatikopoulos, Panagiotis

PY - 2020/12/29

Y1 - 2020/12/29

N2 - 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 Tg (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.

AB - 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 Tg (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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DO - 10.1021/acsomega.0c03056

M3 - 文章

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SP - 32883

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JO - ACS Omega

JF - ACS Omega

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ER -

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

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