Article

# Observation of spin-glass behavior in nickel adsorbed few layer graphene

Journal of Applied Physics (Impact Factor: 2.19). 04/2012; 113(2). DOI: 10.1063/1.4774062
Source: arXiv

ABSTRACT Nickel-adsorbed graphene was prepared by first synthesizing graphite oxide
(GO) by modified Hummers' method and then reducing a solution containing both
GO and $Ni^{2+}$. EDX analysis showed 31 atomic percent nickel was present.
Magnetization measurements under both dc and ac magnetic fields were carried
out in the temperature range 2 K to 300 K. The zero field cooled and field
cooled magnetization data showed a pronounced irreversibility at a temperature
around 20 K. The analysis of the ac susceptibility data were carried out by
both Vogel-Fulcher as well as power law. From dynamic scaling analysis the
microscopic flipping time $\tau_{0}\sim 10^{-13} s$ and critical exponent
$z\nu=5.9\pm0.1$ were found, indicating presence of conventional spin glass in
the system. The spin glass transition temperature was estimated as 19.5 K.
Decay of thermoremanent magnetization (TRM) was explained by stretched
exponential function with a value of the exponent as 0.6 .
From the results it is concluded that nickel adsorbed graphene behaves like a
spin-glass.

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• ##### Article: The peak effect (PE) region of the antiferromagnetic two layer Ising nanographene
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ABSTRACT: In this work, the magnetic properties of the ferromagnetic and antiferromagnetic two layer spin-1/2 Ising nanographene systems are investigated within the effective field theory. We find that the magnetizations and the hysteresis behaviors of the central graphene atoms are similar to those of the edge graphene atoms in the ferromagnetic case. But, they are quite different in the antiferromagnetic case. The antiferromagnetic central graphene atoms exhibit type II superconductivity and they have triple hysteresis loop. The peak effect (PE) region is observed on the hysteresis curves of the antiferromagnetic Ising nanographene system. Therefore, we suggest that there is a strong relationship between the antiferromagnetism and the peak effect. Our results are in agreement with some experimental works in recent literature.
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