Size Dependent Magnetization and High-Vacuum Annealing Enhanced Ferromagnetism in Zn1−xCoxO Nanowires

Diameter controllable ZnO nanowires have been fabricated by thermal evaporation (vapor transport) with various sizes of gold nanoparticles as catalysts. Diluted magnetic semiconductor (DMS) Zn1−xCoxO nanowires were then made by high energy Co ion implantation. The as-implanted and the argon-annealed Zn1−xCoxO nanowires displayed weak ferromagnetism while the high-vacuum annealed nanowires exhibited strong ferromagnetic ordering at room temperature. Size dependent behavior has been observed in the magnetic field and temperature dependences of magnetization. The shrinkage of the nanowire diameter reduced the spontaneous magnetization as well as the hysteresis loops. Field cooled and zero-field cooled magnetization and coercivity measurements were performed between 2 and 300 K to study the evolution of magnetism from the weak to the strong ferromagnetic states. In particular, superparamagnetic features were observed and shown to be intrinsic characteristics of the DMS Zn1−xCoxO nanowires. The room-temperature spontaneous magnetization of individual Zn1−xCoxO nanowires was also established by using magnetic force microscope measurements.

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Room temperature ferromagnetism in diluted magnetic semiconductor Zn1−xCrxTe nanoparticles synthesized by chemical method

Applied Physics Letters ◽

10.1063/1.2931705 ◽

2008 ◽

Vol 92 (20) ◽

pp. 202502 ◽

Cited By ~ 10

Author(s):

Yutaka Niwayama ◽

Hiroaki Kura ◽

Tetsuya Sato ◽

Migaku Takahashi ◽

Tomoyuki Ogawa

Keyword(s):

Chemical Method ◽

Room Temperature ◽

Diluted Magnetic Semiconductor ◽

Room Temperature Ferromagnetism ◽

Magnetic Semiconductor ◽

Diluted Magnetic

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Room-temperature ferromagnetism in Fe-doped, Fe- and Cu-codoped ZnO diluted magnetic semiconductor

Materials Letters ◽

10.1016/j.matlet.2006.11.139 ◽

2007 ◽

Vol 61 (17) ◽

pp. 3605-3607 ◽

Cited By ~ 73

Author(s):

Hua-Wei Zhang ◽

Zhi-Ren Wei ◽

Zhi-Qiang Li ◽

Guo-Yi Dong

Keyword(s):

Room Temperature ◽

Diluted Magnetic Semiconductor ◽

Room Temperature Ferromagnetism ◽

Magnetic Semiconductor ◽

Diluted Magnetic

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Deposits of iron oxides in the human globus pallidus

Open Physics ◽

10.1515/phys-2019-0030 ◽

2019 ◽

Vol 17 (1) ◽

pp. 291-298

Author(s):

Helena Svobodová ◽

Jana Hlinková ◽

Pavol Janega ◽

Daniel Kosnáč ◽

Barbora Filová ◽

...

Keyword(s):

Electron Microscopy ◽

Human Brain ◽

Iron Oxides ◽

Globus Pallidus ◽

Room Temperature ◽

Hysteresis Loops ◽

Point Of View ◽

Zero Field ◽

Fixed Temperature ◽

Transmission Electron

Abstract Samples taken from the human brain (Globus Pallidus) have been investigated by physical techniques such as light microscopy, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy and SQUID magnetometry. SEM-EDX/TEM investigation reveals multielemental composition of hematite and magnetite nanocrystals with sizes ranging from 40 nm to 100 nm and hematite microcrystals from 3 μm to 7 μm. Room temperature Mössbauer spectra show quadrupole doublets assigning to hematite and ferrihydrite. SQUID measurements of temperature dependence of the mass magnetic susceptibility between T = 2 – 300 K at DC field B0 = 0.1 T, the field dependence of the mass magnetization taken at the fixed temperature T0 = 2.0 and 4.6 K and the zero-field cooled and field cooled magnetization experiments (ZFCM/FCM) confirm a presence of ferrimagnetic phases such as maghemite and/or magnetite with hysteresis loops surviving until the room temperature. Differences between these measurements from the point of view of iron oxides detected can indicate important processes in human brain and interactions between ferritin as a physiological source of iron and surrounding environment.

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Room temperature ferromagnetism of Fe-doped ZnO and MgO thin films prepared by ink-jet printing

MRS Proceedings ◽

10.1557/opl.2012.824 ◽

2012 ◽

Vol 1394 ◽

Cited By ~ 3

Author(s):

Mei Fang ◽

Wolfgang Voit ◽

Adrica Kyndiah ◽

Yan Wu ◽

Lyubov Belova ◽

...

Keyword(s):

Thin Films ◽

Room Temperature ◽

Diluted Magnetic Semiconductor ◽

Room Temperature Ferromagnetism ◽

Magnetic Semiconductor ◽

Ink Jet ◽

Jet Printing ◽

Doped Zno ◽

Diluted Magnetic ◽

Magnetic Insulator

ABSTRACTRoom temperature magnetic properties of un-doped, as well as 10 at.% Fe-doped ZnO and MgO single-pass layer of ink-jet printed thin films have been investigated to obtain insight into the role of the band gaps and mechanisms for the origin of ferromagnetic order in these materials. It is found that on doping with Fe, the saturation magnetization is enhanced by several-fold in both systems when compared with the respective un-doped thin films. For a “28 nm thick film of Fe-doped ZnO (Diluted Magnetic Semiconductor, DMS) we observe an enhanced moment of 0.465μB /Fe atom while it is around 0.111μB/Fe atom for the doped MgO (Diluted Magnetic Insulator, DMI) film of comparable thickness. Also, the pure ZnO is far more ferromagnetic than pure MgO at comparable low film thicknesses which can be attributed to defect induced magnetism originating from cat-ion vacancies. However, the film thickness dependence of the magnetization and the defect concentrations are found to be significantly different in the two systems so that a comparison of the magnetism becomes more complex for thicker films.

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