2024-03-28T22:04:48Z
https://soar-ir.repo.nii.ac.jp/oai
oai:soar-ir.repo.nii.ac.jp:00012319
2022-12-14T04:05:59Z
1221:1222
Magnetic and electronic properties of bimagnetic materials comprising cobalt particles within hollow silica decorated with magnetite nanoparticles
Okada, T
Gonzalez-Alfaro, Y
Espinosa, A
Watanabe, N
Haeiwa, T
Sonehara, M
Mishima, S
Sato, T
Munoz-Noval, A
Aranda, P
Garcia-Hernandez, M
Ruiz-Hitzky, E
Bimagnetic materials were fabricated by decorating the external surface of rattle-type hollow silica microspheres (which themselves contain metallic cobalt nanoparticles) with magnetite nanoparticles; thus, each magnetic substance was spatially isolated by the silica shell. The amount of magnetite decoration on the co-occluded hollow silica was varied from 1 to 17 mass %. Magnetic and electronic properties of the resulting bimagnetic materials were characterized by superconducting quantum interference device measurements and X-ray absorption spectroscopy, respectively. The ferrous iron in the bimagnetic sample was slightly more oxidized than in the magnetite reference, probably from some charge-transfer because of the SiO2 surface contact, although the overall oxidation state of the samples is very similar to that of magnetite. The temperature dependence of the sample magnetization recorded with Zero Field Cooling and Field Cooling resulted in blocking temperatures for the bimagnetic materials that were close to that of magnetite nanoparticles (176K) and were lower than that for the bare Co-occluded hollow silica (which was above room temperature). Values of coercive force and exchange bias at 300K became quite small after decoration with only minimal amounts of magnetite nanoparticles (1-3 mass %) and were lower than those of magnetite. This is the first example of enhancing superparamagnetism by spatial separation of both Co and magnetite magnetic nanoparticles using a thin wall of diamagnetic silica.
Article
JOURNAL OF APPLIED PHYSICS. 114(12):124304 (2013)
journal article
AMER INST PHYSICS
2013-09-28
application/pdf
JOURNAL OF APPLIED PHYSICS
12
114
124304
0021-8979
AA00693547
https://soar-ir.repo.nii.ac.jp/record/12319/files/Magnetic_electronic_properties_bimagnetic_materials.pdf
eng
10.1063/1.4822299
https://doi.org/10.1063/1.4822299
Copyright© 2013 AIP Publishing LLC.