Non-Fermi Liquid Behavior of Magnetization near
the Quantum Critical Point in Ni3Al Nanoparticles
with and without Core-shell Structure
Umasankar Meesala and Sharika Nandan Kaul*
School of Physics, University of Hyderabad, Central University P.O., Hyderabad-500046,
Andhra Pradesh, India.
*
Corresponding author’s e-mail: kaul.sn@gmail.com, Tel.: 0091 - 40 - 23134322; Fax: 0091 - 40 - 23010227
Abstract
Strong experimental evidence for non-Fermi liquid behavior
of magnetization in Ni3Al nanoparticles with average crystallite sizes of 50 nm and 5 nm (with NiO shell) is presented.
Keywords: Non-Fermi liquid behavior, core-shell nanoparticles, quantum critical point
Introduction
Previous investigations [1-3] of magnetization, electrical- and magneto-transport in Ni3Al have revealed that
the reduction of the average crystallite size to d ≃ 50
nm drives the weak itinerant-electron ferromagnet Ni3Al
to magnetic instability (quantum critical point), where
the long-range ferromagnetic order collapses. Non-Fermi liquid (NFL) behavior (𝜌(T) ~ T 5/3 for 4K ≤ T ≤
22K) and antiferromagnetic spin fluctuation-mediated
superconductivity at (T < 4 K) have already been inferred [2] from electrical resistivity, 𝜌(T), in nanocrystalline (nc-) Ni3Al with d ≃ 50 nm. In this paper, evidence is provided for the NFL behavior of magnetization in nc-Ni3Al with d ≅ 50 nm (without core-shell
structure) and d ≅ 5 nm (with Ni3Al core- NiO shell
structure).
Results and discussion
Synthesis and characterization details for the nc-Ni3Al
samples are given elsewhere [3]. Figure 1 demonstrates
that magnetization, M, varies with temperature as
M(T, H) = M(0, H) [1 - a(H) T 4/3] in the nc-Ni3Al
sample with d ≅ 5 nm and that the coefficient a of the
T 4/3 term has the H 1/3 power law dependence on the
external magnetic field, H (see inset). Similar behavior
of M(T, H) has been observed in the sample with d ≃ 50
nm except that the exponent n in the T n term in this case
depends on H. According to the spin fluctuation theories
of non-Fermi liquid behavior [4], magnetization (or
susceptibility) should follow the T 4/3 power law behavior in the case of a three-dimensional ferromagnet
near the quantum critical point. The data presented in
Fig. 1 thus provide a strong experimental evidence for
Fig. 1: T 4/3 dependence of magnetization at all fields.
Inset shows H 1/3 variation of a(H).
the NFL behavior in both the nc-Ni3Al samples.
Acknowledgment
This work was supported by the Department of Science
and Technology, India, under Grant no: SP/S2/JCB18/2010. U.M. thanks the University Grants Commission, India, for the financial support in the form of SRF.
References
[1] S. N. Kaul, Anita Semwal and H. –E. Schefer,
Phys. Rev. B, 62, (2000), 13892.
[2] A.C. Abhyankar and S. N. Kaul, Appl. Phys. Lett,
89, (2006), 193125.
[3] U. Meesala, S. N. Kaul, Physica B (2014),
http://dx.doi.org/10.1016/j.physb.2014.03.005.
[4] G R. Stewart, Rev. Mod. Phys, 73, (2001), 797.