Magnetic ordered states induced by interparticle magnetostatic interaction in α-Fe/Au mixed nanoparticle assembly.
The magnetic behavior of α-Fe/Au nanoparticle (NP) assemblies is studied over a very wide range of dipolar interactions among α-Fe NPs, by changing the volume density of the α-Fe NP. The assembly whose α-Fe NP density is lower than 0.1% exhibits typical superparamagnetic behavior. When Fe NP density exceeds 8.6% the magnetic dynamics changes to that resembling superspin glass. Moreover, NP assembly with highest Fe concentration (43%), whose dipolar interaction is enormously strong compared with previous studies, exhibits a two-stage magnetic transition, i.e., ferromagnetic and spin glass-like transitions at 385 K and around 150 K, respectively. Therefore, we first observed the reentrant spin glass-like magnetism at the limit of strong interaction in a close-packed NP assembly. Based on these observations, the magnetic phase diagram of the interacting α-Fe NP assembly is determined over a very wide range of interaction.
Department of Applied Physics & Physico-Informatics, Faculty of Science and Technology, Keio University, Yokohama, 223-8522, Japan.
Kosuke
K
Hiroi
Hiroaki
H
Kura
Tomoyuki
T
Ogawa
Migaku
M
Takahashi
Tetsuya
T
Sato
D006046:Gold / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D060526:Magnetic Fields; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D044367:Phase Transition; D055672:Static Electricity
D006046:Gold; D007501:Iron