title: Magnetic and magnetoelectric properties of self-assembled Fe₂.₅Mn₀.₅O₄ nanocrystals.
abstract: We report magnetoresistance of -40%, corresponding to 80% spin polarization, at magnetic field of 0.5 T and 200 K for oleic acid-coated Fe(2.5)Mn(0.5)O(4) nanocrystals (FMO NCs) self-assembled on a SiO(2)/Si substrate by drop casting fabrication. The FMO NCs exhibited spin glass transition around 150 K and nonlinear current-voltage (I-V) characteristics. Fowler-Nordheim plot of the I-V characteristics indicated that electrons tunnel directly barriers between the FMO NCs. Transmission electron microscopy revealed that the FMO NCs are elongated hexagon in shape with size of ∼15 × 20 nm. The FMO NCs self-assembled in two-dimension hexagonal networks of collinear ferromagnetic moments. The [111] easy magnetization axis of each FMO NC was parallel to each other in the hexagonal arrays. Geometrically frustrated lattice of collinear ferromagnetic moments supports both a low and a high intergranular tunneling conductance for the self-assembled FMO NCs without and with magnetic fields, respectively.
authors.affiliation: Department of Materials Science, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan. kohiki@che.kyutech.ac.jp
authors.forename: Shigemi
authors.initials: S
authors.lastname: Kohiki
authors.forename: Koichi
authors.initials: K
authors.lastname: Okada
authors.forename: Masanori
authors.initials: M
authors.lastname: Mitome
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kohno
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Koichiro
authors.initials: K
authors.lastname: Iyama
authors.forename: Fumiya
authors.initials: F
authors.lastname: Tsunawaki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Deguchi
mesh_terms: D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D019301:Oleic Acid / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013696:Temperature
chemical_list: D019301:Oleic Acid; D012822:Silicon Dioxide; D012825:Silicon