scholarly journals Synthesis and Magnetic Properties of Hematite Particles in a “Nanomedusa” Morphology

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Jin Bae Lee ◽  
Hae Jin Kim ◽  
Janez Lužnik ◽  
Andreja Jelen ◽  
Damir Pajić ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Magnetic Phase ◽  
Hydrothermal Process ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Morin Transition ◽  
Preferential Direction ◽  
X Ray ◽  
Transmission Electron

We present the synthesis, characterization, and magnetic properties of hematite particles in a peculiar “nanomedusa” morphology. The particles were prepared from an iron-silica complex by a hydrothermal process in a solution consisting of ethyl acetate and ethanol. The particles’ morphology, structure, and chemical composition were investigated by transmission electron microscopy, powder X-ray diffraction, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The “hairy” particles consist of a spherical-like core of about 100 nm diameter and fibrous exterior composed of thin “legs” of 5 nm diameter grown along one preferential direction. The particles’ cores are crystalline and undergo a magnetic phase transition to a weakly ferromagnetic state at a temperature of 930 K that matches reasonably the Néel temperature of bulk hematite. However, unlike bulk hematite that undergoes Morin transition to an antiferromagnetic state around room temperature and small hematite nanoparticles that are superparamagnetic, the “nanomedusa” particles remain weakly ferromagnetic down to the lowest investigated temperature of 2 K. Each particle thus represents a nanodimensional “hairy” ferromagnet in a very broad temperature interval, extending much above the room temperature. Such high-temperature ferromagnetic nanoparticles are not frequently found among the nanomaterials.

scholarly journals Fabrication and magnetic properties of hierarchical nickel microwires with nanothorns

2010 ◽  
Vol 8 (2) ◽  
pp. 434-439 ◽  
Author(s):  
Junhao Zhang ◽  
Ling Yang ◽  
Xiaofang Cheng ◽  
Jinmeng Zhang ◽  
Fucai Li
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Magnetic Properties ◽  
Room Temperature ◽  
Cooperative Effect ◽  
Magnetic Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

AbstractHierarchical nickel microwires with nanothorns were fabricated through a reduction of nickelous salt with hydrazine in diethanolamine. The product was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The growth mechanism of the nickel microwires with nanothorns is proposed, based on the evolution of the structures and morphologies, which could be ascribed to the cooperative effect of the complexant of diethanolamine and inherent magnetic interactions. Magnetic properties of the product were measured at room temperature and compared with other shaped counterparts.

IMPROVEMENT OF COERCIVITY IN COBALT-DOPED ANATASE TiO2 NANOPARTICLES HYDROTHERMALLY PREPARED

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2550-2555
Author(s):  
MINGZAI WU ◽  
YING XIONG ◽  
NAN JIANG ◽  
HAI PING QI ◽  
QIANWANG CHEN
Keyword(s):  
Room Temperature ◽  
Magnetic Measurement ◽  
Hydrothermal Process ◽  
Hysteresis Loops ◽  
Anatase Tio2 ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Measurement Results ◽  
Ferromagnetic Hysteresis

Anatase Ti 1-x Co x O 2 nanoparticles were prepared by a hydrothermal process at 180 °C. Ferromagnetic hysteresis loops of the as-prepared samples were measured at room temperature. The Ti 1-x Co x O 2 ( x = 0.0376) powder shows coercivity up to 700 Oe, which is the highest value reported for anatase Ti 1-x Co x O 2. X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurement results provided evidence that Co was incorporated into TiO 2 lattice. Combined with the fact that the preparation was carried out in an oxidized environment starting from cobalt (II) in the oxidized state, it is suggested that the homogeneous doping of Co into the lattice of anatase should be responsible for the improvement of coercivity in anatase Ti 1-x Co x O 2 nanoparticles.

Y-Type Hexaferrites: Structural, Dielectric and Magnetic Properties

2012 ◽  
Vol 189 ◽  
pp. 209-232 ◽  
Author(s):  
Rajshree B. Jotania ◽  
Hardev Singh Virk
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Room Temperature ◽  
Structural Changes ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lcr Meter ◽  
Co Precipitation

This paper attempts to provide a historical survey of structure of various types of hexaferrites. It provides information about synthesis, characterization, structural, magnetic and dielectric properties of Y-type hexagonal ferrites using various chemical routes. We have prepared a series of cobalt doped Sr2Cu2-xCoxFe12O22(x = 0.0 to 1.0) hexaferrites using a wet chemical co-precipitation technique. The prepared hexaferrite precursors were calcined at 950 °C for 4 hours in a furnace and slowly cooled to room temperature. The crystal structure of Y-type hexaferrites is rather complicated. The chemical and structural changes were examined in detail by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), and Fourier transform infra-red (FTIR) spectroscopy. X-ray diffraction studies showed that sintering temperature as low as 950°C was sufficient to produce a single-phase Y-type hexaferrite material. The dielectric measurements were carried out over the frequency range of 100 Hz to 2 MHz at room temperature using an LCR meter to study the variation of dielectric constant and loss tangent with frequency. The magnetic properties of hexaferrite samples were investigated using a vibration sample magnetometer (VSM), and a superconducting quantum interference device (SQUID) magnetometer in the temperature range 30K to 200K. A change from ferromagnetic state to super paramagnetic state has been observed in Co doped Sr2Cu2-xCoxFe12O22(x= 0.6 to 1.0) hexaferrite. The novel applications of all types of hexaferrite materials have been described.

Magnetic CoFe2O4/carbon nanotubes composites: fabrication, microstructure and magnetic response

2014 ◽  
Vol 28 (12) ◽  
pp. 1450095 ◽  
Author(s):  
Panfeng Wang ◽  
Jingcai Xu ◽  
Yanbing Han ◽  
Bo Hong ◽  
Hongxiao Jin ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Magnetic Properties ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Targeting Therapy ◽  
X Ray ◽  
Transmission Electron ◽  
Tumor Hyperthermia ◽  
Temperature Time ◽  
Microstructure And Magnetic Properties

By combining the unique microstructure of carbon nanotubes (CNTs) with the good magnetism of CoFe 2 O 4 ferrites, CoFe 2 O 4/CNTs nanocomposites were prepared by the solvothermal method for the application of targeting therapy and tumor hyperthermia. X-ray diffraction (XRD), thermal gravity analysis (TGA), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) were introduced to study the influence of the solvothermal temperature, time and the CNTs content on the microstructure and magnetic properties of CoFe 2 O 4/CNTs nanocomposites. The diameter of CoFe 2 O 4 nanoparticles coating on the surface of CNTs and the saturation magnetization (Ms) increased with the solvothermal temperature. CoFe 2 O 4/CNTs nanocomposites prepared at 180°C, 200°C and 220°C exhibited superparamagnetism at room temperature, while the samples prepared at 240°C and 260°C presented ferromagnetism. And the solvothermal time and CNTs content slightly affected the microstructure and magnetic properties, Ms and coercivity (Hc) increased slightly with the increasing solvothermal time and the decreasing CNTs content.

scholarly journals Preparation and Magnetic Properties of ZnFe2O4Nanotubes

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Yan Xu ◽  
Yantian Liang ◽  
Lijuan Jiang ◽  
Huarui Wu ◽  
Hongzhi Zhao ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Anodic Aluminum Oxide Template ◽  
Blocking Temperature ◽  
Outer Diameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anodic Aluminum ◽  
Transmission Electron

Ordered ZnFe2O4nanotube arrays with the average outer diameter of 100 nm were prepared in porous anodic aluminum oxide template using an improved sol-gel approach. The morphology was studied by transmission electron and field emission scanning electron microscope. X-ray diffraction result shows that the nanotubes were polycrystalline in structure. The magnetic properties of the prepared ZnFe2O4nanotubes were also studied. The results show that the sample shows typical superparamagnetism at room temperature and obvious ferromagnetism below blocking temperature.

Preparation, Characterization and Magnetic Property of MFe2O4 (m=Mn, Zn, Ni, Co) Nanoparticles

2013 ◽  
Vol 842 ◽  
pp. 35-38 ◽  
Author(s):  
Li Xia Yang ◽  
Sha Li ◽  
Jing Zhang ◽  
Zhou Chen ◽  
Shi Cheng Xu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetic Properties ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Basic Source ◽  
Co Nanoparticles ◽  
Zn Nanoparticles

MFe2O4 (M=Mn, Co, Ni, Zn) Nanoparticles with diameters from 5nm to 30nm have been prepared through a hydrothermal method. In this system, ethanolamine was used as a basic source instead of NaOH. The as-prepared ferrites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the magnetic properties of the obtained ferrites have been studied at room temperature, showing that the magentic properties of ferrites closely depended on the chemical composition of M2+.

scholarly journals Size Effect on the Structural and Magnetic Properties of Nanosized PerovskiteLaFeO3Prepared by Different Methods

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Nguyen Thi Thuy ◽  
Dang Le Minh
Keyword(s):  
Magnetic Properties ◽  
Electron Microscope ◽  
Room Temperature ◽  
High Energy ◽  
Ferromagnetic Behavior ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation

Nanosized LaFeO3material was prepared by 3 methods: high energy milling, citrate gel, and coprecipitation. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) show that the orthorhombic LaFeO3phase was well formed at a low sintering temperature of 500°C in the citrate-gel and co-precipitation methods. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations indicate that the particle size of the LaFeO3powder varies from 10 nm to 50 nm depending on the preparation method. The magnetic properties through magnetization versus temperatureM(T)and magnetization verses magnetic fieldM(H)characteristics show that the nano-LaFeO3exhibits a weak ferromagnetic behavior in the room temperature, and theM(H)curves are well fitted by Langevin functions.

FABRICATION OF BaFe12O19 NANOWIRES BY A HYDROTHERMAL PROCESS AND THEIR MAGNETIC PROPERTIES

2006 ◽  
Vol 20 (07) ◽  
pp. 359-364 ◽  
Author(s):  
JUN WANG ◽  
YUEJIN ZHU
Keyword(s):  
Electron Microscopy ◽  
Saturation Magnetization ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Hydrothermal Process ◽  
Annealing Treatment ◽  
Magnetization Measurement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

Magnetic BaFe 12 O 19 nanowires have been prepared by a hydrothermal process. The nanowires with diameters ~ 15 nm and lengths ~ 2 μ m are clearly visible in Transmission Electron Microscopy (TEM) image. The physical properties of the BaFe 12 O 19 nanowires were further characterized by X-ray diffraction (XRD) and magnetization measurement. The results of the magnetization measurement show that the sample displays ferromagnetic properties at room temperature and its saturation magnetization (Ms) reaches 13.36 emu/g. Annealing treatment of the sample in air at 800°C leads to the increasing of the saturation magnetization (Ms: 65.7 emu/g). It is suggested that the oxygen vacancies should be responsible for the low saturation magnetization, which is also supported by the magnetic property (Ms: 21.6 emu/g) of the sample annealed at 800°C in argon shield.

MICROSTRUCTURE AND MAGNETIC PROPERTIES CHANGE OF Fe3O4 NANOPARTICLES SYNTHESIZED UNDER MAGNETIC FIELDS AT ROOM TEMPERATURE

2009 ◽  
Vol 23 (23) ◽  
pp. 2723-2731 ◽  
Author(s):  
JUN WANG ◽  
SIHUA XIA ◽  
SHIHE CAO
Keyword(s):  
Magnetic Properties ◽  
Magnetic Fields ◽  
Room Temperature ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Promising Technique ◽  
X Ray ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Microstructure And Magnetic Properties

Magnetite nanoparticles have been synthesized by a co-precipitation method under magnetic fields (0~1 T) at room temperature. The as-prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and their microstructure analysis were evaluated on a Mössbauer spectrum. It was found that the Fe 3 O 4 samples produced under a magnetic field of 1 T had a much higher saturation magnetization (15.3 emu/g) than those produced under 0.6 T (7.56 emu/g) and 0 T magnetic fields (6.59 emu/g). This interesting result implies that magnetic fields can affect the growth of Fe 3 O 4 nanoparticles and further change the microstructure and crystallinity of Fe 3 O 4 nanoparticles. It is expected that this process could also be a promising technique to improve the magnetic properties of other magnetic materials.

Preparation of FeCoZrBCu Thin Films and their Effect of Microstructure on Magnetic Properties

2007 ◽  
Vol 546-549 ◽  
pp. 2163-2166
Author(s):  
Jia Ping Cui ◽  
Li Zhong ◽  
Xiao Fang Bi
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Amorphous State ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
X Ray ◽  
Cu Films ◽  
Si Substrates ◽  
Transmission Electron ◽  
Deposited Films

In this work, (Fe,Co)–Zr–B–Cu films have been deposited on glass and Si substrates by DC magnetron sputtering method. X-ray diffraction analysis was used to identify the structure of the films. A transmission electron microscope (TEM) was employed to observe the microstructure for the films. Magnetic properties at room temperature were investigated by a Vibrating Sample Magnetometer (VSM). It was obtained that the as-deposited films on glass and Si substrates were in an amorphous state. In addition, it has been found that the coercivity is dependent on film thicknesses.

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