Dragana Marković - Academia.edu (original) (raw)

Papers by Dragana Marković

Molecular carcinogenesis, Feb 24, 2016

It has been shown that angiogenesis and inflammation play an important role in development of mos... more It has been shown that angiogenesis and inflammation play an important role in development of most hematological malignancies including the myeloproliferative neoplasm (MPN). The aim of this study was to investigate and correlate the levels of key angiogenic molecules such as hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) in peripheral blood and bone marrow cells of MPN patients, along with JAK2V617F mutation allele burden and effects of therapy. HIF-1α and VEGF gene expression were decreased, while eNOS mRNA levels were increased in granulocytes of MPN patients. Furthermore, positively correlated and increased VEGF and eNOS protein levels were in negative correlation with HIF-1α levels in granulocytes of MPN patients. According to immunoblotting, the generally augmented angiogenic factors demonstrated JAK2V617F allele burden dependence only in granulocytes of PMF. The angiogenic factors were largely reduc...

Scripta Materialia, 2007

Nanoscale maghemite samples were obtained by a solid-state displacement reaction activated by mec... more Nanoscale maghemite samples were obtained by a solid-state displacement reaction activated by mechanochemical treatment for two different milling times, 30 min (sample S1) and 4 h (sample S2). Samples were characterized by X-ray powder diffraction, transmission electron microscopy and SQUID magnetometry. The results show that prolongation of the milling time increases particle size while reducing the crystallinity, with a strong impact on the magnetic properties. Coercivity of 3.3 kOe at 5 K temperature for S2 is among the highest values reported so far for the maghemite nanoparticles.

Solid State Communications, 2003

Magnetic properties of the dinuclear cobalt complex [Co 2 (ox)tpmc](ClO 4 ) 2 ·3H 2 O have been s... more Magnetic properties of the dinuclear cobalt complex [Co 2 (ox)tpmc](ClO 4 ) 2 ·3H 2 O have been studied from the magnetization data obtained in the high magnetic field-low temperature experiment (B # 20 T; T ¼ 4:2 K). An excellent agreement between experimental and calculated data was achieved within the framework of the isolated Ising Co(II) pairs in the ground state, where each cobalt ion from the pair was situated in a differently distorted octahedral environment ('asymmetric dimer'). The obtained values for g-factors; g a ¼ ð4:5^0:1Þ and g b ¼ ð3:3^0:1Þ; and for the intracluster exchange integral J ¼ ð216:0^0:5Þ K confirm both the previous results on the crystal structure of the complex under consideration and the assumption on the strong antiferromagnetic coupling between cobalt ions realized by the superexchange interaction over the asymmetric oxalato bridge. q

Scripta Materialia, 2008

ABSTRACT Starting from a nanocomposite consisting of 4 nm hematite nanoparticles embedded in a si... more ABSTRACT Starting from a nanocomposite consisting of 4 nm hematite nanoparticles embedded in a silica matrix (30 wt.% hematite) and by applying heat treatments at increasing temperatures up to 1050 °C, gradual formation of ε-Fe2O3 phase was obtained. Besides representing a new synthesis route of ε-Fe2O3 phase, the results obtained in this work indicate that under certain conditions hematite nanoparticles are not thermally stable. Hence, like other ferric oxide polymorphs, nanosized hematite can undergo thermally triggered, size-induced structural phase transitions.

Scripta Materialia, 2008

Nanoparticle La0. 7Ca0. 3MnO3 was synthesized for the first time by the glycine–nitrate method wi... more Nanoparticle La0. 7Ca0. 3MnO3 was synthesized for the first time by the glycine–nitrate method without additional heat treatment. The average crystallite size of∼ 10nm obtained by both transmission electron microscopy and X-ray diffraction was among the smallest ...

Materials Letters, 2009

The α-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol–gel method ... more The α-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol–gel method and characterized by using X-ray diffractometer (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) ...

Materials Letters, 2010

We report on the synthesis, morphology and magnetic properties of a novel NiO/SiO2 nanostructure.... more We report on the synthesis, morphology and magnetic properties of a novel NiO/SiO2 nanostructure. The NiO/SiO2 nanostructure was synthesized by a method based on the contribution of sol–gel and combustion processes. X-ray powder diffraction (XRPD) ...

Journal of Magnetism and Magnetic Materials, 2009

The α-Fe2O3/SiO2 nanocomposite containing 45wt% of hematite was prepared by the sol–gel method fo... more The α-Fe2O3/SiO2 nanocomposite containing 45wt% of hematite was prepared by the sol–gel method followed by heating in air at 200° C. The so-obtained composite of iron (III) nanoparticles dissolved in glassy silica matrix was investigated by X-ray powder ...

Journal of Magnetism and Magnetic Materials, 2004

The influence of the magnetic ions dilution on the crystal and magnetic structures of CoxZn1− xO ... more The influence of the magnetic ions dilution on the crystal and magnetic structures of CoxZn1− xO (x= 1, 0.90, 0.83, 0.75) solid solutions has been studied by the neutron diffraction and magnetic susceptibility measurements. It has been concluded that ...

Journal of Magnetism and Magnetic Materials, 2008

Comparative crystal structure and magnetic properties studies have been conducted on quaternary p... more Comparative crystal structure and magnetic properties studies have been conducted on quaternary powder spinel samples LiMn1. 82Cr0. 18O4 obtained by two different synthesis methods, glycine-nitrate (GN) and ultrasonic spray-pyrolysis (SP). Although both samples ...

Journal of Alloys and Compounds, 2014

ABSTRACT We report on ferromagnetic-like magnetic properties, at room temperature, of spherical n... more ABSTRACT We report on ferromagnetic-like magnetic properties, at room temperature, of spherical nickel oxide core–shell nanoparticles synthesized by sol–gel combustion method. The sample is characterized by using transmission electron microscopy (TEM), selected electron area diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RS) and superconducting quantum interference device (SQUID) magnetometer. The SAED, EDX and RS show high quality and purity of the sample. The TEM images point to core–shell NiO nanostructure with a well crystallized NiO core and surface disorder shell. The size of the nanoparticles of about 5 nm and thickness of the surface shell below 1 nm are estimated from the TEM and HRTEM measurements. The measurements of the magnetization reveals ferromagnetic-like behavior of the sample at room temperature with remanent magnetization Mr = 0.0087 emu/g and coercive field HC = 115 Oe. These magnetic properties are quite different than in NiO bulk materials and uncommon for nanosized NiO materials. These results also indicate that the synthesized NiO core–shell nanostructure is suitable for spin-valve applications.

Journal of Alloys and Compounds, 2007

Hematite nanoparticles in a silica matrix containing 30wt.% of hematite were synthesized by the s... more Hematite nanoparticles in a silica matrix containing 30wt.% of hematite were synthesized by the sol–gel method. Transmission electron microscopy studies showed that the average particle size of the hematite was about 4nm with a narrow size distribution, while selected ...

Journal of Alloys and Compounds, 2010

The influence of the heat treatment on the structural and magnetic properties of the nanoparticle... more The influence of the heat treatment on the structural and magnetic properties of the nanoparticle La 0.7 Ca 0.3 MnO 3 compound has been studied. The starting single-phase sample was prepared by the glycine-nitrate method without additional heating. The as-prepared specimen has been afterward annealed at two different temperatures of 600 • C and 900 • C. All three samples where characterized by XRPD, SEM and TEM, as well as by the SQUID magnetometry. Rietveld analysis of the XRPD data showed the orthorhombic perovskite structure (space group Pnma) of all the samples, while the unit cell parameters underwent a contraction with the annealing temperature. The influence of the heat treatment on the crystal structure is to decrease the orthorhombic distortion by changing the geometrical parameters. The TEM micrographs showed the increase of the mean particle size with annealing temperature from 10 nm up to 50 nm. DC magnetization and AC susceptibility measurements revealed the change of magnetic properties with the increase of the particle size: both para-to-ferromagnetic transition temperature T C and saturation magnetization M S were shifted to higher values with the simultaneous decrease of the coercivity H C . In addition, annealing procedure suppresses the spin-glass-like state that emerges in the as-prepared sample below T f = 95 K.

Journal of Alloys and Compounds, 2011

We have observed unusual magnetic properties of NiO (nickel oxide) nanoparticles embedded in a si... more We have observed unusual magnetic properties of NiO (nickel oxide) nanoparticles embedded in a silica matrix. The sample was synthesized by a method based on the contribution of sol-gel and combustion processes. X-ray powder diffraction (XRPD) of the sample shows the formation of the nanocrystalline NiO phase whereas transmission electron microscope (TEM) reveals spherical-shaped nanoparticles of about 4 nm diameter. Moreover, HRTEM images show lattice fringes of the nanoparticles and defects in the crystal structure. The temperature and field dependence of the magnetization are also measured. The zero-field-cooled (ZFC) measurements show two maximums, one sharp and narrow at low temperatures ∼6.5 K and an other broad one at higher temperature ∼64 K. The FC magnetization shows a continuous increase upon lowering the temperature. The M(H) measurements reveal that NiO nanoparticles display anomalous hysteretic behaviors at low temperatures (below the low temperature maximum in the ZFC curve, 2 K and 5 K) showing that the magnetization initial curve lies below the hysteresis loop for a certain field range. Moreover, jump of the magnetization at low temperatures (2 K and 5 K) are also observed. These features represent novel magnetic properties for nanosized NiO which may be attributed to the surface spins. Moreover, these results indicate that the NiO nanoparticle consists of magnetically disorder shell and antiferromagnetically order core with an uncompensated magnetic moment.

Journal of Alloys and Compounds, 2012

ABSTRACT We report on magnetic properties of iron oxide nanoparticles in a silica matrix synthesi... more ABSTRACT We report on magnetic properties of iron oxide nanoparticles in a silica matrix synthesized by the sol–gel method. The sample is characterized by using X-ray powder diffractometer (XRPD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and superconducting quantum interference device (SQUID) magnetometer. TEM reveals iron oxide nanoparticles (maghemite/magnetite) of small sizes of about 4 nm, narrow size distribution and no particle agglomeration. The SQUID measurements show low blocking temperature TB = 6 K and superparamagnetic behavior above 30 K. Obtained saturation magnetization MS = 61.1 emu/g is very high, among the highest values for iron oxides of particle size below 5 nm. The field-cooled hysteresis measurements do not show displacement of the hysteresis loop thus indicating an absence of exchange bias, whereas AC susceptibility reveals non-interacting nanoparticles. The values of Keff and KS (effective and surface anisotropy constants) obtained in this work are smaller than those reported in the literature for systems where shell's disorder spin structure (surface effects) is observed. These results point to highly crystalline iron oxide nanoparticles with a low amount of internal defects and small surface disorder shell thickness which is uncommon for nanoparticles of this size. Superparamagnetic iron oxide nanoparticles (SPION) with such properties are convenient for the biomedical applications in targeted diagnostics and drug delivery.

Journal of Alloys and Compounds, 2012

We found novel and superior magnetic properties of the hematite (a-Fe 2 O 3 ) that originate from... more We found novel and superior magnetic properties of the hematite (a-Fe 2 O 3 ) that originate from an internal microstructure of particles and strong inter-particle interactions between nanocrystal sub-units. The hematite particles were synthesized by thermal decomposition of iron (III) nitrate without any template or surfactant. The purity, size, crystallinity, morphology, microstructure and magnetic features of the asprepared particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and SQUID magnetometry. An XRD study reveals a pure phase of a-Fe 2 O 3 whereas TEM shows a-Fe 2 O 3 spheres with a diameter of about 150 nm. RS also shows high quality and purity of the sample. Moreover, TEM and HRTEM images show a pomegranate-like superstructure and evidence that the spherical particles are composed of individual well-crystallized nanoparticle sub-units (self-assembled nanoparticles) with a size of about 20 nm. Magnetic measurements display hysteretic behavior at the room temperature with remanent magnetization M r = 0.731 emu/g, saturation magnetization M S = 6.83 emu/g and coercivity H C = 4350 Oe, as well as the Morin transition at T M = 261 K. These results and comparison with those in the literature reveal that the sample has extremely high coercivity. The magnetic properties of the sample are discussed in relation to morphology, internal microstructure, surface effects and exchange and dipole-dipole interactions.

Journal of Alloys and Compounds, 2009

We report on morphological, structural and magnetic properties of α-Fe2O3 nanoparticles in an amo... more We report on morphological, structural and magnetic properties of α-Fe2O3 nanoparticles in an amorphous alumina matrix synthesized by aqueous combustion method. The sample was characterized by X-ray powder diffraction (XRPD), high-resolution electron microscopy (HREM) and SQUID magnetometry. XRPD study reveals the phase purity of α-Fe2O3 whereas HREM images show an unusual spongy structure and well-crystallized nanoparticles with a size of about 25 nm. Magnetic measurements show a high irreversibility temperature Tirr ≈ 350 K, Morin transition at TM ≈ 210 K, increase of the magnetization below T ≈ 45 K and hysteretic behavior below TM at 5 K and 200 K.

Journal of Alloys and Compounds, 2011

We report on hydrothermal synthesis, plate-like morphology, microstructure and magnetic propertie... more We report on hydrothermal synthesis, plate-like morphology, microstructure and magnetic properties of hematite (α-Fe2O3) plate-like particles. The sample is obtained immediately after the hydrothermal process without using any template and without further heat treatment. The so-obtained sample is characterized by X-ray powder diffraction (XRPD), energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and superconducting quantum interference device (SQUID) magnetometer. XRPD confirms the formation of a single-phase hematite sample whereas EDX reveals that iron and oxygen are the only components of the sample. SEM, FE-SEM, TEM and HRTEM show that the sample is composed of plate-like particles. The width of the particles is ∼500 nm whereas thickness is ∼100 nm (aspect ratio 5:1). The HRTEM images exhibit well defined lattice fringes of α-Fe2O3 particles that confirm their high crystallinity. Moreover, the HRTEM analysis indicates the plate-like particles preferring crystal growth along [0 1 2] direction. Magnetic measurements display significant hysteretic behavior at room temperature with coercivity HC = 1140 Oe, remanent magnetization Mr = 0.125 emu/g and saturation magnetization MS = 2.15 emu/g as well as the Morin transition at TM ∼ 250 K. The magnetic properties are discussed with respect to morphology and microstructure of the particles. The results and comparison with urchin-like, rods, spherical, hexagonal, star-like, dendrites, platelets, irregular, nanoplatelets, nanocolumns and nanospheres hematites reveal that the plate-like particles possess good magnetic properties. One may conjecture that the shape anisotropy plays an important role in the magnetic properties of the sample.► Plate-like hematite α-Fe2O3 particles were prepared by template-free hydrothermal route. ► The micrographs show a width of the plate-like particles of ∼500 nm and a thickness of ∼100 nm (aspect ratio ∼ 5). ► The HRTEM shows perfect lattice fringes and preferring crystal growth along [0 1 2] direction. ► The values of the coercivity, remanent magnetization and saturation magnetization at room temperature are HC = 1140 Oe, Mr = 0.125 emu/g and MS = 2.15 emu/g, respectively. ► The Morin temperature is observed at TM ≈ 250 K.

Molecular carcinogenesis, Feb 24, 2016

It has been shown that angiogenesis and inflammation play an important role in development of mos... more It has been shown that angiogenesis and inflammation play an important role in development of most hematological malignancies including the myeloproliferative neoplasm (MPN). The aim of this study was to investigate and correlate the levels of key angiogenic molecules such as hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) in peripheral blood and bone marrow cells of MPN patients, along with JAK2V617F mutation allele burden and effects of therapy. HIF-1α and VEGF gene expression were decreased, while eNOS mRNA levels were increased in granulocytes of MPN patients. Furthermore, positively correlated and increased VEGF and eNOS protein levels were in negative correlation with HIF-1α levels in granulocytes of MPN patients. According to immunoblotting, the generally augmented angiogenic factors demonstrated JAK2V617F allele burden dependence only in granulocytes of PMF. The angiogenic factors were largely reduc...

Scripta Materialia, 2007

Nanoscale maghemite samples were obtained by a solid-state displacement reaction activated by mec... more Nanoscale maghemite samples were obtained by a solid-state displacement reaction activated by mechanochemical treatment for two different milling times, 30 min (sample S1) and 4 h (sample S2). Samples were characterized by X-ray powder diffraction, transmission electron microscopy and SQUID magnetometry. The results show that prolongation of the milling time increases particle size while reducing the crystallinity, with a strong impact on the magnetic properties. Coercivity of 3.3 kOe at 5 K temperature for S2 is among the highest values reported so far for the maghemite nanoparticles.

Solid State Communications, 2003

Magnetic properties of the dinuclear cobalt complex [Co 2 (ox)tpmc](ClO 4 ) 2 ·3H 2 O have been s... more Magnetic properties of the dinuclear cobalt complex [Co 2 (ox)tpmc](ClO 4 ) 2 ·3H 2 O have been studied from the magnetization data obtained in the high magnetic field-low temperature experiment (B # 20 T; T ¼ 4:2 K). An excellent agreement between experimental and calculated data was achieved within the framework of the isolated Ising Co(II) pairs in the ground state, where each cobalt ion from the pair was situated in a differently distorted octahedral environment ('asymmetric dimer'). The obtained values for g-factors; g a ¼ ð4:5^0:1Þ and g b ¼ ð3:3^0:1Þ; and for the intracluster exchange integral J ¼ ð216:0^0:5Þ K confirm both the previous results on the crystal structure of the complex under consideration and the assumption on the strong antiferromagnetic coupling between cobalt ions realized by the superexchange interaction over the asymmetric oxalato bridge. q

Scripta Materialia, 2008

ABSTRACT Starting from a nanocomposite consisting of 4 nm hematite nanoparticles embedded in a si... more ABSTRACT Starting from a nanocomposite consisting of 4 nm hematite nanoparticles embedded in a silica matrix (30 wt.% hematite) and by applying heat treatments at increasing temperatures up to 1050 °C, gradual formation of ε-Fe2O3 phase was obtained. Besides representing a new synthesis route of ε-Fe2O3 phase, the results obtained in this work indicate that under certain conditions hematite nanoparticles are not thermally stable. Hence, like other ferric oxide polymorphs, nanosized hematite can undergo thermally triggered, size-induced structural phase transitions.

Scripta Materialia, 2008

Nanoparticle La0. 7Ca0. 3MnO3 was synthesized for the first time by the glycine–nitrate method wi... more Nanoparticle La0. 7Ca0. 3MnO3 was synthesized for the first time by the glycine–nitrate method without additional heat treatment. The average crystallite size of∼ 10nm obtained by both transmission electron microscopy and X-ray diffraction was among the smallest ...

Materials Letters, 2009

The α-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol–gel method ... more The α-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol–gel method and characterized by using X-ray diffractometer (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) ...

Materials Letters, 2010

We report on the synthesis, morphology and magnetic properties of a novel NiO/SiO2 nanostructure.... more We report on the synthesis, morphology and magnetic properties of a novel NiO/SiO2 nanostructure. The NiO/SiO2 nanostructure was synthesized by a method based on the contribution of sol–gel and combustion processes. X-ray powder diffraction (XRPD) ...

Journal of Magnetism and Magnetic Materials, 2009

The α-Fe2O3/SiO2 nanocomposite containing 45wt% of hematite was prepared by the sol–gel method fo... more The α-Fe2O3/SiO2 nanocomposite containing 45wt% of hematite was prepared by the sol–gel method followed by heating in air at 200° C. The so-obtained composite of iron (III) nanoparticles dissolved in glassy silica matrix was investigated by X-ray powder ...

Journal of Magnetism and Magnetic Materials, 2004

The influence of the magnetic ions dilution on the crystal and magnetic structures of CoxZn1− xO ... more The influence of the magnetic ions dilution on the crystal and magnetic structures of CoxZn1− xO (x= 1, 0.90, 0.83, 0.75) solid solutions has been studied by the neutron diffraction and magnetic susceptibility measurements. It has been concluded that ...

Journal of Magnetism and Magnetic Materials, 2008

Comparative crystal structure and magnetic properties studies have been conducted on quaternary p... more Comparative crystal structure and magnetic properties studies have been conducted on quaternary powder spinel samples LiMn1. 82Cr0. 18O4 obtained by two different synthesis methods, glycine-nitrate (GN) and ultrasonic spray-pyrolysis (SP). Although both samples ...

Journal of Alloys and Compounds, 2014

ABSTRACT We report on ferromagnetic-like magnetic properties, at room temperature, of spherical n... more ABSTRACT We report on ferromagnetic-like magnetic properties, at room temperature, of spherical nickel oxide core–shell nanoparticles synthesized by sol–gel combustion method. The sample is characterized by using transmission electron microscopy (TEM), selected electron area diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (RS) and superconducting quantum interference device (SQUID) magnetometer. The SAED, EDX and RS show high quality and purity of the sample. The TEM images point to core–shell NiO nanostructure with a well crystallized NiO core and surface disorder shell. The size of the nanoparticles of about 5 nm and thickness of the surface shell below 1 nm are estimated from the TEM and HRTEM measurements. The measurements of the magnetization reveals ferromagnetic-like behavior of the sample at room temperature with remanent magnetization Mr = 0.0087 emu/g and coercive field HC = 115 Oe. These magnetic properties are quite different than in NiO bulk materials and uncommon for nanosized NiO materials. These results also indicate that the synthesized NiO core–shell nanostructure is suitable for spin-valve applications.

Journal of Alloys and Compounds, 2007

Hematite nanoparticles in a silica matrix containing 30wt.% of hematite were synthesized by the s... more Hematite nanoparticles in a silica matrix containing 30wt.% of hematite were synthesized by the sol–gel method. Transmission electron microscopy studies showed that the average particle size of the hematite was about 4nm with a narrow size distribution, while selected ...

Journal of Alloys and Compounds, 2010

The influence of the heat treatment on the structural and magnetic properties of the nanoparticle... more The influence of the heat treatment on the structural and magnetic properties of the nanoparticle La 0.7 Ca 0.3 MnO 3 compound has been studied. The starting single-phase sample was prepared by the glycine-nitrate method without additional heating. The as-prepared specimen has been afterward annealed at two different temperatures of 600 • C and 900 • C. All three samples where characterized by XRPD, SEM and TEM, as well as by the SQUID magnetometry. Rietveld analysis of the XRPD data showed the orthorhombic perovskite structure (space group Pnma) of all the samples, while the unit cell parameters underwent a contraction with the annealing temperature. The influence of the heat treatment on the crystal structure is to decrease the orthorhombic distortion by changing the geometrical parameters. The TEM micrographs showed the increase of the mean particle size with annealing temperature from 10 nm up to 50 nm. DC magnetization and AC susceptibility measurements revealed the change of magnetic properties with the increase of the particle size: both para-to-ferromagnetic transition temperature T C and saturation magnetization M S were shifted to higher values with the simultaneous decrease of the coercivity H C . In addition, annealing procedure suppresses the spin-glass-like state that emerges in the as-prepared sample below T f = 95 K.

Journal of Alloys and Compounds, 2011

We have observed unusual magnetic properties of NiO (nickel oxide) nanoparticles embedded in a si... more We have observed unusual magnetic properties of NiO (nickel oxide) nanoparticles embedded in a silica matrix. The sample was synthesized by a method based on the contribution of sol-gel and combustion processes. X-ray powder diffraction (XRPD) of the sample shows the formation of the nanocrystalline NiO phase whereas transmission electron microscope (TEM) reveals spherical-shaped nanoparticles of about 4 nm diameter. Moreover, HRTEM images show lattice fringes of the nanoparticles and defects in the crystal structure. The temperature and field dependence of the magnetization are also measured. The zero-field-cooled (ZFC) measurements show two maximums, one sharp and narrow at low temperatures ∼6.5 K and an other broad one at higher temperature ∼64 K. The FC magnetization shows a continuous increase upon lowering the temperature. The M(H) measurements reveal that NiO nanoparticles display anomalous hysteretic behaviors at low temperatures (below the low temperature maximum in the ZFC curve, 2 K and 5 K) showing that the magnetization initial curve lies below the hysteresis loop for a certain field range. Moreover, jump of the magnetization at low temperatures (2 K and 5 K) are also observed. These features represent novel magnetic properties for nanosized NiO which may be attributed to the surface spins. Moreover, these results indicate that the NiO nanoparticle consists of magnetically disorder shell and antiferromagnetically order core with an uncompensated magnetic moment.

Journal of Alloys and Compounds, 2012

ABSTRACT We report on magnetic properties of iron oxide nanoparticles in a silica matrix synthesi... more ABSTRACT We report on magnetic properties of iron oxide nanoparticles in a silica matrix synthesized by the sol–gel method. The sample is characterized by using X-ray powder diffractometer (XRPD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and superconducting quantum interference device (SQUID) magnetometer. TEM reveals iron oxide nanoparticles (maghemite/magnetite) of small sizes of about 4 nm, narrow size distribution and no particle agglomeration. The SQUID measurements show low blocking temperature TB = 6 K and superparamagnetic behavior above 30 K. Obtained saturation magnetization MS = 61.1 emu/g is very high, among the highest values for iron oxides of particle size below 5 nm. The field-cooled hysteresis measurements do not show displacement of the hysteresis loop thus indicating an absence of exchange bias, whereas AC susceptibility reveals non-interacting nanoparticles. The values of Keff and KS (effective and surface anisotropy constants) obtained in this work are smaller than those reported in the literature for systems where shell's disorder spin structure (surface effects) is observed. These results point to highly crystalline iron oxide nanoparticles with a low amount of internal defects and small surface disorder shell thickness which is uncommon for nanoparticles of this size. Superparamagnetic iron oxide nanoparticles (SPION) with such properties are convenient for the biomedical applications in targeted diagnostics and drug delivery.

Journal of Alloys and Compounds, 2012

We found novel and superior magnetic properties of the hematite (a-Fe 2 O 3 ) that originate from... more We found novel and superior magnetic properties of the hematite (a-Fe 2 O 3 ) that originate from an internal microstructure of particles and strong inter-particle interactions between nanocrystal sub-units. The hematite particles were synthesized by thermal decomposition of iron (III) nitrate without any template or surfactant. The purity, size, crystallinity, morphology, microstructure and magnetic features of the asprepared particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and SQUID magnetometry. An XRD study reveals a pure phase of a-Fe 2 O 3 whereas TEM shows a-Fe 2 O 3 spheres with a diameter of about 150 nm. RS also shows high quality and purity of the sample. Moreover, TEM and HRTEM images show a pomegranate-like superstructure and evidence that the spherical particles are composed of individual well-crystallized nanoparticle sub-units (self-assembled nanoparticles) with a size of about 20 nm. Magnetic measurements display hysteretic behavior at the room temperature with remanent magnetization M r = 0.731 emu/g, saturation magnetization M S = 6.83 emu/g and coercivity H C = 4350 Oe, as well as the Morin transition at T M = 261 K. These results and comparison with those in the literature reveal that the sample has extremely high coercivity. The magnetic properties of the sample are discussed in relation to morphology, internal microstructure, surface effects and exchange and dipole-dipole interactions.

Journal of Alloys and Compounds, 2009

We report on morphological, structural and magnetic properties of α-Fe2O3 nanoparticles in an amo... more We report on morphological, structural and magnetic properties of α-Fe2O3 nanoparticles in an amorphous alumina matrix synthesized by aqueous combustion method. The sample was characterized by X-ray powder diffraction (XRPD), high-resolution electron microscopy (HREM) and SQUID magnetometry. XRPD study reveals the phase purity of α-Fe2O3 whereas HREM images show an unusual spongy structure and well-crystallized nanoparticles with a size of about 25 nm. Magnetic measurements show a high irreversibility temperature Tirr ≈ 350 K, Morin transition at TM ≈ 210 K, increase of the magnetization below T ≈ 45 K and hysteretic behavior below TM at 5 K and 200 K.

Journal of Alloys and Compounds, 2011

We report on hydrothermal synthesis, plate-like morphology, microstructure and magnetic propertie... more We report on hydrothermal synthesis, plate-like morphology, microstructure and magnetic properties of hematite (α-Fe2O3) plate-like particles. The sample is obtained immediately after the hydrothermal process without using any template and without further heat treatment. The so-obtained sample is characterized by X-ray powder diffraction (XRPD), energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and superconducting quantum interference device (SQUID) magnetometer. XRPD confirms the formation of a single-phase hematite sample whereas EDX reveals that iron and oxygen are the only components of the sample. SEM, FE-SEM, TEM and HRTEM show that the sample is composed of plate-like particles. The width of the particles is ∼500 nm whereas thickness is ∼100 nm (aspect ratio 5:1). The HRTEM images exhibit well defined lattice fringes of α-Fe2O3 particles that confirm their high crystallinity. Moreover, the HRTEM analysis indicates the plate-like particles preferring crystal growth along [0 1 2] direction. Magnetic measurements display significant hysteretic behavior at room temperature with coercivity HC = 1140 Oe, remanent magnetization Mr = 0.125 emu/g and saturation magnetization MS = 2.15 emu/g as well as the Morin transition at TM ∼ 250 K. The magnetic properties are discussed with respect to morphology and microstructure of the particles. The results and comparison with urchin-like, rods, spherical, hexagonal, star-like, dendrites, platelets, irregular, nanoplatelets, nanocolumns and nanospheres hematites reveal that the plate-like particles possess good magnetic properties. One may conjecture that the shape anisotropy plays an important role in the magnetic properties of the sample.► Plate-like hematite α-Fe2O3 particles were prepared by template-free hydrothermal route. ► The micrographs show a width of the plate-like particles of ∼500 nm and a thickness of ∼100 nm (aspect ratio ∼ 5). ► The HRTEM shows perfect lattice fringes and preferring crystal growth along [0 1 2] direction. ► The values of the coercivity, remanent magnetization and saturation magnetization at room temperature are HC = 1140 Oe, Mr = 0.125 emu/g and MS = 2.15 emu/g, respectively. ► The Morin temperature is observed at TM ≈ 250 K.