TY - JOUR
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
N1 - Publisher Copyright:
© 2020 American Chemical Society. All rights reserved.
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.
UR - http://www.scopus.com/inward/record.url?scp=85098961506&partnerID=8YFLogxK
U2 - 10.1021/acsomega.0c03056
DO - 10.1021/acsomega.0c03056
M3 - 文章
AN - SCOPUS:85098961506
SN - 2470-1343
VL - 5
SP - 32883
EP - 32889
JO - ACS Omega
JF - ACS Omega
IS - 51
ER -