Comparison of the magnetic properties of metastable hexagonal close-packed Ni nanoparticles with those of the stable face-centered cubic Ni nanoparticles

Yoon Tae Jeon, Je Yong Moon, Gang Ho Lee, Jeunghee Park, Yongmin Chang

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Abstract

We report the first magnetic study of pure and metastable hexagonal close-packed (hep) Ni nanoparticles (sample 1). We also produced stable face-centered cubic (fcc) Ni nanoparticles, as mixtures with the hcp Ni nanoparticles (samples 2 and 3). We compared the magnetic properties of the hcp Ni nanoparticles with those of the fcc Ni nanoparticles by observing the evolution of magnetic properties from those of the hcp Ni nanoparticles to those of the fcc Ni nanoparticles as the number of fcc Ni nanoparticles increased from sample 1 to sample 3. The blocking temperature (TB) of the hcp Ni nanoparticles is ∼12 K for particle diameters ranging between 8.5 and 18 nm, whereas those of the fcc Ni nanoparticles are 250 and 270 K for average particle diameters of 18 and 26 nm, respectively. The hcp Ni nanoparticles seem to be antiferromagnetic for T < TB and paramagnetic for T > TB. This is very different from the fcc Ni nanoparticles, which are ferromagnetic for T < TB and superparamagnetic for T > T B. This unusual magnetic state of the metastable hcp Ni nanoparticles is likely related to their increased bond distance (2.665 Å), compared to that (2.499 Å) of the stable fcc Ni nanoparticles.

Original languageEnglish
Pages (from-to)1187-1191
Number of pages5
JournalJournal of Physical Chemistry B
Volume110
Issue number3
DOIs
StatePublished - 26 Feb 2006

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