Search results for: P.C. Fannin

Items from 1 to 20 out of 53 results

article

The concept of ferrofluid preheating in the treatment of cancer by magnetic hyperthermia of tissues

I. Malaescu, P.C. Fannin, C.N. Marin, D. Lazic

Medical Hypotheses > 2018 > 110 > C > 76-79

The frequency dependence of the complex magnetic susceptibility, χ(ω) = χ′(ω) − i χ″(ω), of a water-based magnetic fluid with magnetite particles, over the frequency range 500 kHz to 2 MHz and at three different temperatures of 30 °C, 40 °C and 50 °C are presented. Based on these experimental measurements, the dependence on frequency, f = (ω/2π) Hz, of the heating rate, ΔT/Δt, of the ferrofluid has...

article

Local arrangement of particles in magnetic fluids due to the measurement alternating field

P.C. Fannin, C.N. Marin, I. Malaescu, K. Raj, more

Journal of Magnetism and Magnetic Materials > 2017 > 438 > C > 116-120

Changes in the magnetic susceptibility spectrum of ferrofluids, χ(ω), due to the nanoparticle agglomeration are common when a static magnetic field is superimposed on the measuring field, but here we report on changes which occur in the absence of a static magnetic field, solely in the presence of the measuring field, over the frequency range of 50Hz–13MHz and irrespective of the colloidal stability...

article

On the determination of the dynamic properties of a transformer oil based ferrofluid in the frequency range 0.1–20GHz

P.C. Fannin, L. Vekas, C.N. Marin, I. Malaescu

Journal of Magnetism and Magnetic Materials > 2017 > 423 > C > 61-65

Complex susceptibility measurements provide a unique and efficient means for the investigation and determination of the dynamic properties of magnetic fluids. In particular, measurement of the frequency, f(Hz), and field, H(kA/m), dependent, complex susceptibility, χ(ω, Η)= χ′(ω, Η)−iχ″(ω, Η), of magnetic fluids has proven to be a valuable and reliable technique for investigating such properties....

article

On the utility of low frequency, polarised, complex susceptibility measurements in the investigation of the dynamic properties of magnetic fluids

Qiang Li, P.C. Fannin, C.N. Marin, I. Malaescu, more

Journal of Molecular Liquids > 2016 > 219 > C > 773-779

The measurement of the field and frequency-dependent, complex susceptibility, χ (ω, Η)=χ′(ω, H)−iχ″ (ω, Η), is an established method for investigating the dynamic properties of magnetic fluids. Polarised measurements have been used to investigate many properties of magnetic fluids, including, relaxation mechanisms, aggregation, magnetic losses, loss factor tanδ, power factor sinδ, and the influence...

article

Time solved susceptibility spectra of magnetic fluids

C.N. Marin, P.C. Fannin, I. Malaescu

Journal of Magnetism and Magnetic Materials > 2015 > 388 > C > 45-48

Measurements of the frequency (f) and polarizing field (H) dependent complex magnetic susceptibility, χ(f, H)=χ′(f, H)–iχ″(f, H) of a magnetic fluid over the frequency range 1kHz to 2MHz, in various polarizing fields from zero to approximately 7kA/m are presented. The sample was a commercial magnetic fluid with magnetite particles in isopar-M.Usually, Brownian relaxation time measurements are involved...

article

An experimental study of the dynamic properties of nanoparticle colloids with identical magnetization but different particle size

P.C. Fannin, C.N. Marin, K. Raj, C. Couper, more

Journal of Magnetism and Magnetic Materials > 2012 > 324 > 21 > 3443-3447

Measurements of the frequency dependent complex magnetic susceptibility, χ(ω)=χ′(ω)−iχ″(ω), have been used to determine the dynamic properties of three specially prepared 400G (0.04T) magnetic fluids. The samples, denoted by sample 1, sample 2 and sample 3, consisted of magnetite particles of mean diameter 6.4nm, 7.5nm and 9nm respectively and were identical in terms of carrier liquid, surfactant...

article

Intra-well relaxation process in magnetic fluids subjected to strong polarising fields

C.N. Marin, P.C. Fannin, I. Mălăescu, P. Barvinschi, more

Journal of Magnetism and Magnetic Materials > 2012 > 324 > 4 > 434-439

We report on the frequency and field dependent complex magnetic susceptibility measurements of a kerosene-based magnetic fluid with iron oxide nanoparticles, stabilized with oleic acid, in the frequency range 0.1–6GHz and over the polarising field range of 0–168.4kA/m.By increasing polarising field, H, a subsidiary loss-peak clearly occurs in the vicinity of the ferromagnetic resonance peak, from...

article

The resonance decay function method in the determination of the pre-factor of the Néel relaxation time of single-domain nanoparticles

P.C. Fannin, C.N. Marin, C. Couper

Journal of Magnetism and Magnetic Materials > 2011 > 323 > 10 > 1242-1245

In its simple form, the relaxation time of the Néel relaxation process of the magnetic moment of single-domain particles is given by τ _N =τ _0N exp(σ), σ being the ratio of anisotropy energy to thermal energy. The pre-factor, τ _0N , is normally given a value of 10 ⁻⁹ s, but values ranging from 10 ⁻⁸ to 10 ⁻¹² s have been reported in literature. Here,...

article

Microwave absorbent properties of nanosized cobalt ferrite powders prepared by coprecipitation and subjected to different thermal treatments

P.C. Fannin, C.N. Marin, I. Malaescu, N. Stefu, more

Materials and Design > 2011 > 32 > 3 > 1600-1604

Cobalt ferrite nanopowders were produced by means of two methods using a common precipitating agent. After precipitation, in the first method the cobalt ferrite was calcined, whilst in the second method the precipitation was followed by a hydrothermal treatment. Characterization of the obtained powders was achieved by X-ray diffraction and scanning electron microscopy–energy dispersive X-ray analysis...

article

An improved technique for the measurement of the complex susceptibility of magnetic colloids in the microwave region

P.C. Fannin, C. MacOireachtaigh, C. Couper

Journal of Magnetism and Magnetic Materials > 2010 > 322 > 16 > 2428-2433

Measurements by means of the short-circuit (S/C) and open circuit (O/C) transmission line techniques are well established methods for investigating the magnetic and dielectric properties of magnetic colloids, respectively. In particular, the S/C technique has been used in the investigation of the resonant properties of ferrofluids; resonance being indicated by the transition of the real component...

article

Investigation of magnetic fluids exhibiting field-induced increasing loss peaks

P.C. Fannin, C.N. Marin, C. Couper

Journal of Magnetism and Magnetic Materials > 2010 > 322 > 9-12 > 1677-1681

A theoretical analysis to explain an increase of the Brownian loss peak with increasing polarizing field, H, in a magnetic fluid, is presented. The model is based on the competition between the Brownian and Néel relaxation processes. It is demonstrated that in magnetic fluids with particles having small anisotropy constant, small average magnetic diameter and narrow particle size distribution an increase...

article

Precessional decay time of nanoparticles in magnetic fluids

P.C. Fannin, C.N. Marin, C. Couper

Journal of Magnetism and Magnetic Materials > 2010 > 322 > 9-12 > 1682-1685

A new experimental method to determine the precessional decay time, τ ₀ , in a strong polarizing field, H, is proposed. The method is based on analysis of the after-effect function of a magnetic fluid at resonance and the experimental results obtained for a sample with Mn _0.3 Fe _0.7 Fe ₂ O ₄ particles reveal that in the region of strong H, τ ₀ decreases...

article

Biasing field effect on the microwave dielectric properties of magnetic fluids

C. Couper, C.N. Marin, P.C. Fannin

Physics Procedia > 2010 > 9 > Complete > 58-62

A theory is presented which shows the biasing field effect on the frequency dependence of the complex dielectric permittivity of magnetic fluids, as measured with a coaxial cell having the axis perpendicular to the biasing field. The theory is supported by measurements on a kerosene based magnetic fluid with magnetite particles, subjected to a biasing field, H of up to 168 kA/m, over the frequency...

article

On the high-frequency measurement of the dynamic properties of nano-particle colloids

P.C. Fannin

Journal of Magnetism and Magnetic Materials > 2009 > 321 > 7 > 850-853

Measurement of the magnetic complex susceptibility, χ(ω)=χ′(ω)−iχ″(ω) by means of the transmission line technique, is a well established method for the determination of the dynamic properties of nano-particle colloids, such as magnetic fluids. From polarising studies one can obtain accurate data on the anisotropy constant, K, anisotropy field, H _A , gyromagnetic constant γ, and the damping...

article

Characteristic times of relaxation peaks of magnetic fluids

P.C. Fannin, C.N. Marin

Journal of Magnetism and Magnetic Materials > 2008 > 320 > 16 > 2106-2111

The use of the Fokker–Planck equation in theoretical studies of relaxation processes in single-domain particle systems is a well-established technique. However this method has a particular disadvantage in that it can give analytical results solely in some limiting cases. An alternative method, which avoids this difficulty, is that of the use of the integral relaxation time, τ _int , which is...

article

Investigation of the non-linear loss properties of magnetic fluids subject to large alternating fields

C. Mac Oireachtaigh, P.C. Fannin

Journal of Magnetism and Magnetic Materials > 2008 > 320 > 6 > 871-880

The non-linear relaxational properties of a water-based magnetic fluid are investigated by means of measuring the frequency dependent complex susceptibility, χ(ω) in the presence of an external potential. The results obtained are discussed in terms of the magnetic analogue of the Coffey and Paranjape model as modified by Déjardin. The loss processes in the magnetic fluid in the non-linear region are...

article

Investigating the isotropic properties of a magnetic fluid following the removal of a polarising field

P.C. Fannin, C. Mac Oireachtaigh

Journal of Magnetism and Magnetic Materials > 2007 > 316 > 2 > e802-e804

Measurement of the frequency and field-dependent, complex susceptibility, χ(ω,H)=χ′(ω,H)-iχ″(ω,H), of magnetic fluids, by means of the toroidal technique, is a well tested method for investigating the dynamic properties of magnetic fluids. It is demonstrate how polarised measurements, with H being varied, cyclically, over the range ±13.6kA/m, can be used to determine the isotropic properties of a...

article

A study of the magnetic properties of mixed ferrite nanoparticles in ferrofluids

A. Amulevicius, D. Baltrunas, K. Mazeika, P.C. Fannin, more

Journal of Molecular Liquids > 2007 > 133 > 1-3 > 152-158

Magnetic properties of Zn _x Co _1−x Fe ₂ O ₄ (x=0.3, 0.5 and 0.7) nanoparticles in ferrofluids have been investigated by means of Mössbauer spectroscopy in the temperature range 4.2–300 K. The mean sizes of the particles were 10.2, 7.4 and 5.2 nm, respectively. The transition temperatures to the superparamagnetic state and values of crystal magnetic anisotropy have been...

article

Determination of the Landau–Lifshitz damping parameter of composite magnetic fluids

P.C. Fannin, I. Malaescu, C.N. Marin

Physica B: Physics of Condensed Matter > 2007 > 388 > 1-2 > 93-98

Measurements of the frequency dependent, complex magnetic susceptibility, χ(ω)=χ′(ω)−iχ″(ω), in the GHz range, are used to investigate the effect which the mixing of two different magnetic fluids has on the value of the damping parameter, α, of the Landau–Lifshitz equation.The magnetic fluid samples investigated in this study were three kerosene-based magnetic fluids, stabilised with oleic acid, denoted...

article

An investigation of the microscopic and macroscopic properties of magnetic fluids

P.C. Fannin, C.N. Marin, I. Malaescu, N. Stefu

Physica B: Physics of Condensed Matter > 2007 > 388 > 1-2 > 87-92

Measurements are presented of the frequency and field dependent complex magnetic susceptibility, χ(ω,H)=χ′(ω,H)-iχ″(ω,H) of three different magnetic fluids, over the frequency and polarizing field (H) ranges of 100MHz to 6GHz and 0–122kA/m, respectively. The investigated samples were Isopar M-based magnetic fluids, with magnetite particles (sample S1), Ni _0.5 Zn _0.5 Fe ₂ O...

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Search results for: P.C. Fannin

The concept of ferrofluid preheating in the treatment of cancer by magnetic hyperthermia of tissues

Local arrangement of particles in magnetic fluids due to the measurement alternating field

On the determination of the dynamic properties of a transformer oil based ferrofluid in the frequency range 0.1–20GHz

On the utility of low frequency, polarised, complex susceptibility measurements in the investigation of the dynamic properties of magnetic fluids

Time solved susceptibility spectra of magnetic fluids

An experimental study of the dynamic properties of nanoparticle colloids with identical magnetization but different particle size

Intra-well relaxation process in magnetic fluids subjected to strong polarising fields

The resonance decay function method in the determination of the pre-factor of the Néel relaxation time of single-domain nanoparticles

Microwave absorbent properties of nanosized cobalt ferrite powders prepared by coprecipitation and subjected to different thermal treatments

An improved technique for the measurement of the complex susceptibility of magnetic colloids in the microwave region

Investigation of magnetic fluids exhibiting field-induced increasing loss peaks

Precessional decay time of nanoparticles in magnetic fluids

Biasing field effect on the microwave dielectric properties of magnetic fluids

On the high-frequency measurement of the dynamic properties of nano-particle colloids

Characteristic times of relaxation peaks of magnetic fluids

Investigation of the non-linear loss properties of magnetic fluids subject to large alternating fields

Investigating the isotropic properties of a magnetic fluid following the removal of a polarising field

A study of the magnetic properties of mixed ferrite nanoparticles in ferrofluids

Determination of the Landau–Lifshitz damping parameter of composite magnetic fluids

An investigation of the microscopic and macroscopic properties of magnetic fluids

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