Interference Device Magnetometer Research Articles

Non-monotonic variation of the Kramers point band gap with increasing magnetic doping in BiTeI

Polar Rashba-type semiconductor BiTeI doped with magnetic elements constitutes one of the most promising platforms for the future development of spintronics and quantum computing thanks to the combination of strong spin-orbit coupling and internal ferromagnetic ordering. The latter originates from magnetic impurities and is able to open an energy gap at the Kramers point (KP gap) of the Rashba bands. In the current work using angle-resolved photoemission spectroscopy (ARPES) we show that the KP gap depends non-monotonically on the doping level in case of V-doped BiTeI. We observe that the gap increases with V concentration until it reaches 3% and then starts to mitigate. Moreover, we find that the saturation magnetisation of samples under applied magnetic field studied by superconducting quantum interference device (SQUID) magnetometer has a similar behaviour with the doping level. Theoretical analysis shows that the non-monotonic behavior can be explained by the increase of antiferromagnetic coupled atoms of magnetic impurity above a certain doping level. This leads to the reduction of the total magnetic moment in the domains and thus to the mitigation of the KP gap as observed in the experiment. These findings provide further insight in the creation of internal magnetic ordering and consequent KP gap opening in magnetically-doped Rashba-type semiconductors.

Synthesis and Magnetic Characterization of La<sub>2-</sub><i><sub>x</sub></i>Sr<i><sub>x</sub></i>CuO<sub>4</sub> Nanoparticles

Non-doped and strontium-doped lanthanum cuprates (La2CuO4 (LCO) and La1.85Sr0.15CuO4 (LSCO15)) in nano-sized particles were synthesized by the chemically dissolved technique employing HNO3 as the dissolving agent. The structural and magnetic properties were investigated by using an x-ray diffraction (XRD) apparatus and a superconducting quantum interference device (SQUID) magnetometer, respectively. The XRD patterns of LCO and LSCO15 show the formation of the single phase without impurities after the calcinations in air at 1100°C for 15 h and the post-annealing in oxygen at 800 °C for 24 h. The average crystallite sizes of LCO and LSCO15 samples were in a range of around 100 nm confirming nano-sized particles. The LCO and LSCO15 nanoparticles exhibit superconductivity at the superconducting (SC) transition temperature, Tc, of 23 K and 38 K, respectively. The magnetization curve measurements have revealed that both samples show the appearance of ferro- and dia-magnetic behavior at room temperature and the appearance of superconductivity at low temperatures. This result may indicate the coexistence of ferromagnetism and superconductivity below Tc in the nano-sized cuprates.

Preliminary Study on the Magnetic Properties of GeMn Nanocolumn/Ge Multilayers

Ge0.94Mn0.06 nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge0.94Mn0.06 nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge0.94Mn0.06(40 nm)/Ge(d nm)]9/Ge0.94Mn0.06(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns.

Size-defined synthesis of magnetic nanorods by Salvia hispanica essential oil with electromagnetic excitation properties useful in microwave imagining

Abstract Salvia hispanica (chia) essential oil was applied for successful production of magnetic nanorods. The influence of several parameters, i.e. temperature of the reaction mixture, volume of the S. hispanica essential oil solution, stirring speed of the reaction mixture, and flow rate of the N2 protective gas, on their axial length was studied. A design of experiments (DOE) approach followed by the response surface methodology (RSM) identified the optimal conditions for synthesis of ∼3 nm magnetic nanorods. The granulometric and magnetic properties of these magnetite nanorods were analyzed using transmission electron microscopy (TEM), energy dispersive X-ray scattering (EDX), selected area electron diffraction spectroscopy (SAED), X-ray diffraction (XRD), and superconducting quantum interference device (SQUID) magnetometer. These methods revealed that the produced magnetic nanorods had a crystalline cubic inverse spinel structure with an average axial length of 43.4 ± 20.5 nm, diameter of 3.6 ± 0.9 nm, and aspect ratio of 12.1 ± 5.2 nm, and they suggested the presence of spin glass-like (mictomagnetic) behavior with both ferro- and antiferromagnetic interactions. In addition, attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) was used to identify functional groups of the organic compounds present in S. hispanica essential oil that were possibly responsible for production and surface functionalization of the magnetite nanorods. The resultant magnetic nanofluid displayed electromagnetic excitation when exposed to microwave radiation, and therefore it could be useful in microwave-imaging of tissues.

Improvement of the Superconducting Properties of GdBa2Cu3O7-δ with Nano-Sized Ferrite Addition

We have been investigating the effect of (CoFe2O4)x and (ZnFe2O4)x (x is the wt%) nano-sized ferrites on the superconducting (SC) properties of the high-Tc SC compound GdBa2Cu3O7-δ (Gd123) prepared by the conventional solid-state reaction technique. In this work, the magnetic hysteresis for pure Gd123 samples and samples added with nano-sized ferrites was measured using a superconducting quantum interference device (SQUID) magnetometer using a dc field up to 30,000 Oe. The magnetic Jc was estimated using the extended Bean model. While a clear increase in Jc values with the addition of (CoFe2O4)x nano-sized ferrites is observed, a less clear positive effect on the Jc values is observed with the addition of (ZnFe2O4)x nano-sized ferrites. These results indicate an improvement of grain connectivity, decrease of voids between the grains, and decrease of porosity in Gd123 compound resulting from CoFe2O4 addition consistent with the mechanical properties measured before. (CoFe2O4)x nano-sized ferrite addition has thus resulted in an improvement in the SC properties of Gd123 high-Tc SC compound making it more convenient for applications.

Investigation of Geomagnetic Orientation Preserved in a Stain Containing Iron Compounds Using a Vector-Type SQUID Magnetometer

We investigate the orientation of the magnetic field preserved in a stain containing iron compounds, such as ink pigment or blood, using a superconducting quantum interference device (SQUID) magnetometer system. The magnetization of a cloth or paper sample is observed by applying a vector-type SQUID gradiometer, which detects three orthogonal components of the magnetic field, and mechanical modulation, which converts dc magnetic signals to time-varying signals detectable by SQUIDs. Numerical experiments indicate that the orientation of the magnetization could be identified by the vector-type SQUID magnetometer when the sample was moved linearly under the probe. This paper describes in detail the instrumentation of the measurement system and a proof-of-principle experiment to confirm the system's effectiveness. The obtained results suggest that the magnetization of iron-compound-containing stains preserved the orientation of the magnetic field in which they were produced, as we hypothesized.

Synthesis and Characterization of Co3O4-MnxCo3-xO4 Core-Shell Nanoparticles

ABSTRACTThe mixed-valence oxide Co3O4 nanoparticles, having the normal spinel structure, possess large surface area, active-site surface adsorption properties, and fast ion diffusivities. Consequently, they are widely used in lithium-ion batteries, as well as for gas sensing and heterogeneous catalysis applications. In our research, we use a two-step method to synthesize Co3O4–based core-shell nanoparticles (CSNs). Cobalt oxide (Co3O4) nanoparticles were successfully synthesized using a wet synthesis method employing KOH and cobalt acetate. Manganese was incorporated into the Co3O4 structure to synthesize inverted Co3O4@MnxCo3-xO4 CSNs using a hydrothermal method. By adjustment of pH value, we obtained two different morphologies of CSNs, one resulting in pseudo-spherical and octahedron-shaped nanoparticles (PS type) whereas the second type predominantly have a nanoplate (NP type) morphology. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS) have been performed in order to determine the morphological and structural properties of our CSNs, whereas the magnetic properties have been characterized using a superconducting quantum interference device (SQUID) magnetometer. XRD and TEM results show that the CSNs have the same spinel crystal structure throughout the core and shell with an average particle size of ∼19.8 nm. Our Co3O4 nanoparticles, as measured prior to CSN formation, are shown to be antiferromagnetic (AFM) in nature as shown by the magnetization data. Our SQUID data indicate that the core-shell nanoparticles have both AFM (due to the Co3O4 core) and ferrimagnetic properties (of the shell) with a coercivity field of 300 Oe and 150 Oe at 5 K for the PS and NP samples, respectively. The magnetization vs temperature data show a spin order-disorder transition at ∼33 K and a superparamagnetic blocking temperature of ∼90 K for both batches.

Magnetic Characterization of Chromium Intermediates in the Reduction of Chromium (VI) by Glutathione in Acidic Solutions

Chromium (VI) is carcinogenic through intermediates formed in the cellular milieu by reduction with small reductants like glutathione (GSH), ascorbate, cysteine, and NADPH. Although the reduction of chromate by thiols has been investigated, the participation of Cr(IV) intermediates has been inferred only indirectly due to the Cr(IV) refractive behavior towards EPR spectroscopy. Biological data from numerous reports indicate that Cr(IV) is the species most likely responsible for the carcinogenicity of Cr(VI). Our kinetic studies suggested that in acidic solutions, glycine buffer at pH 2.8, the reduction of chromate with GSH involves mostly a chromium(IV) intermediate. As a step towards the full characterization of the paramagnetic species involved in the reduction of chromate by thiols at neutral pH, we embarked on an investigation of the reduction of chromate with GSH in glycine buffer at pH 2.8 using a Superconducting QUantum Interference Device (SQUID) magnetometer. Our results indicate a strong influence of temperature and confirm the presence of Cr(IV). At 2 K, the saturation magnetization method was applied to the frozen reaction when it reached the peak of formation of intermediates and the contributions were calculated to be 30% of Cr(IV) and 69% of Cr(V). When the Curie–Weiss method was applied to determine the effective magnetic moment, the use of the linear portion of the curve, 100–200 K, yielded 58% Cr(IV) and 42% Cr(V); when data from the region below the temperature of liquid N2 (77 K) is employed, the intermediate is exclusively Cr(IV).

T112. Visualization of electrical activities in the carpal tunnel area by magnetoneurography of median nerve

Introduction In recent years, diagnosis of the carpal tunnel syndrome is mainly performed by electrophysiological examination. In particular, the utility and reliability of inching method were demonstrated by some reports. However, electrophysiological examination is affected by the surrounding tissues such as bone and soft tissue, and the inching method is not technically easy and requires many electrodes. On the other hand, the magnetic field is not affected by the surrounding tissue. We have developed the magnetometer for the spinal cord and the spinal nerve activity and succeeded in measuring electrophysiological activity in the spinal cord and spinal nerve roots. Now, we are working on magnetoneurography (MNG) which is measurement of magnetic fields generated by the peripheral nerve. In this study, we aimed to evaluate spatiotemporal spread of digital nerve-evoked currents in the median nerve at the carpal tunnel area using MNG. Methods Using a newly developed superconducting quantum interference device (SQUID) magnetometer, neuromagnetic fields of 9 healthy volunteers’ hands were measured at the surface of the carpal tunnel area after stimulation of the digital nerves at the index or middle finger. Current sources were estimated using spatial filter techniques and were superimposed on X-ray images of the hand. We set a virtual electrode in the carpal tunnel along the median nerve. We reconstructed the current waveform from the magnetic field and calculated the nerve conduction velocity from the peak latency. We also measured sensory nerve action potential just above the carpal tunnel, 3 cm distal and 3 cm proximal to the carpal tunnel in response to stimulation of the digital nerves of the index finger. The conduction velocity was calculated from the peak latency. Results Neuromagnetic fields propagating from the finger to the wrist were successfully measured in all subjects. Distribution of action currents calculated from MNG showed the axonal activity pattern showing the intra-axonal current and the depolarization/ repolarization current. Nerve conduction velocity estimated from the MNG was 55.3 m/s and corresponded with the sensory nerve conduction velocity. Conclusion We could visualize action current at any point in carpal tunnel with high resolution using MNG. Moreover, MNG is not affected by the surrounding bone and soft tissues and can be fused with morphological images such as X-rays. MNG is expected to contribute to the clinical diagnosis and treatment of carpal tunnel syndrome.

O-1-13. Diagnosis of lumbar radiculopathy using magnetospinography

Introduction We previously reported noninvasive visualization of neural activities in the lumbar spine using magnetospinography (MSG). We report here MSG findings of a patient with lumbar radiculopathy. Methods Using a newly developed superconducting quantum interference device (SQUID) magnetometer, we measured the neuromagnetic fields of a patient with L4/-5 disc herniation at the surface of the lumbar spine area after stimulation of the peroneal nerves at the fibular head. Current sources were estimated using spatial filter techniques and were superimposed on X-ray images of the lumbar spine. Results and discussion The action currents calculated from MSG showed a distribution pattern of axonal activity with an intra-axonal current and depolarization/repolarization current. On the contralateral healthy side, the nerve action current passed through the L5 intervertebral foramen and propagated in the caudal-to-cranial direction. On the affected side, the nerve action current attenuated at the L4/-5 intervertebral disc level. Thus, noninvasive surface MSG visualizes propagating spinal nerve excitation in response to peroneal nerve stimulation with high spatial and temporal resolution, allowing us to quantitatively evaluate the decreased action current in lumbar radiculopathy. MSG obtains a different perspective from MRI for the diagnosis of neuropathic pain and is expected to be a clinically useful modality.

Enhanced Ferromagnetism in Nanoscale GaN:Mn Wires Grown on GaN Ridges.

The problem of weak magnetism has hindered the application of magnetic semiconductors since their invention, and on the other hand, the magnetic mechanism of GaN-based magnetic semiconductors has been the focus of long-standing debate. In this work, nanoscale GaN:Mn wires were grown on the top of GaN ridges by metalorganic chemical vapor deposition (MOCVD), and the superconducting quantum interference device (SQUID) magnetometer shows that its ferromagnetism is greatly enhanced. Secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy (EDS) reveal an obvious increase of Mn composition in the nanowire part, and transmission electron microscopy (TEM) and EDS mapping results further indicate the correlation between the abundant stacking faults (SFs) and high Mn doping. When further combined with the micro-Raman results, the magnetism in GaN:Mn might be related not only to Mn concentration, but also to some kinds of built-in defects introduced together with the Mn doping or the SFs.

Development of SQUID magnetometer with direct-feedback noise cancellation for magnetocardiogram without magnetically shielded room

Superconducting quantum interference device (SQUID) magnetometers have been widely used to perform biomagnetic measurements. In biomagnetic measurements such as magnetocardiograms (MCGs) and magnetoencephalograms, a magnetically shielded room (MSR) is used for noise reduction. However, because the MSR is expensive and heavy, the environments in which it can be used are restricted. In addition, MCG measurements obtained outside the MSR have a poor signal-to-noise ratio. We developed a wide dynamic range SQUID magnetometer that uses the flux-quanta counting (FQC) method with direct-feedback noise cancellation for MCG measurements and does not require the MSR. The FQC method is used to expand the dynamic range of the SQUID magnetometers to enable MCG measurements outside the MSR in the presence of large magnetic noise. The noise cancellation system uses two SQUID sensors; one for sensing and another one for reference. Both the sensing and reference signals are fed back to the sensing SQUID. This makes it possible to reduce the magnetic noise. We demonstrated the dynamic range, noise spectrum of the developed SQUID system, and MCG waveforms measured outside the MSR when the noise cancellation was set to ON or OFF. The noise cancellation factor of the developed SQUID system ranged from 10 to 20 dB. In MCG waveforms with noise cancellation, the QRS complex and T wave were clearly observed. The results show that the developed SQUID system clearly measures MCG waveforms in a condition involving large environmental magnetic noise.

Room Temperature Antiferromagnetic Ordering of Nanocrystalline Tb1.90Ni0.10O3

Nanocrystalline Ni-doped terbium oxide (Tb1.90Ni0.10O3) has been synthesized by the co-precipitation method followed by annealing at 700°C for 6 h in vacuum. The crystallographic phase and the substitution of Ni2+ ions in the lattice of Tb2O3 are confirmed by Rietveld analysis of the x-ray diffraction pattern using the software MAUD. High-resolution transmission electron microscopy is also carried out to study the morphology of the sample. Magnetic measurements are carried out at different temperatures from 5 K to 300 K using a superconducting quantum interference device (SQUID) magnetometer. The dependence of the magnetization of Tb1.90Ni0.10O3 as a function of temperature (M–T) and magnetic field (M–H) suggests the presence of both paramagnetic and antiferromagnetic phase at room temperature, but antiferromagnetic phase dominates below ∼120 K. The lack of saturation in the M–H curve and good fitting of the M–T curve by the Johnston formula also indicate the presence of both paramagnetic and antiferromagnetic phase at room temperature. Interestingly, an antiferromagnetic to ferromagnetic phase transition is observed below ∼40 K. The result also shows a high value of magnetization at 5 K.

Hydrothermal synthesis of self-assembly Co nanospheres and their magnetic properties

Uniform Co nanospheres with an average diameter of 445 nm were generated conveniently by a simple hydrothermal route in the solution mixed of water and ethanol (v/v = 1 : 2) under the assistance of surfactant polyvinyl pyrrolidone (PVP). The products were characterised by XRD, EDX, SEM, TEM and superconducting quantum interference device (SQUID) magnetometer. The role of PVP in the forming of Co nanospheres was researched. The results indicated that PVP plays a crucial role on the morphology and size of the products. Moreover, a tentative explanation for the growth mechanism of Co nanospheres was proposed. The room-temperature hysteresis loop of these nanospheres shows a ferromagnetic behaviour with enhanced coercivity.

Wide Dynamic Range Analog Flux-Locked Loop System Using Low-<italic>T</italic><sub>c</sub> SQUID for MCG Measurements Without MSR

Recently, biomagnetic measurements using a superconducting quantum interference device (SQUID) magnetometer have been widely performed and utilized for clinical applications. In biomagnetic measurements, such as magnetocardiogram (MCG) and magnetoencephalogram, a magnetically shielded room (MSR) is used for noise reduction. However, because the MSR is expensive and heavy, there is a problem to which used environment is restricted. We developed an analog flux-locked loop system (low-Tc SQUID magnetometer) using the flux-quanta counting (FQC) method for MCG measurements, which does not require the MSR. This FQC-based system is operated using high-speed analog switches and comparators to realize a wide dynamic range. The comparator is given in the hysteresis property for stability behavior. We show the noise spectrum, dynamic range of the developed analog system and MCG waveforms measured inside and outside the MSR. The developed analog system can measure MCG waveforms (~30 pT) under large environmental magnetic noise (~1000 pT) conditions.

Room Temperature Ferromagnetism in ZnO/SnO<SUB>2</SUB> Nanotubes by Electrospinning

ZnO/SnO2 nanotubes are prepared by electrospinning method with postannealing in air at 500 degrees C. Field emission scanning electron microscopy (FE-SEM) reveals the formation of porous ZnO/SnO2 nanotubes. The X-ray diffraction (XRD) and Raman spectrum results show that the ZnO/SnO2 nanotubes have mixed of wurtzite (ZnO) and rutile (SnO2) structure. High-resolution transmission electron microscopy (HRTEM) results also assist the products polycrystalline nature with an average outer diameter of similar to 300 nm, a wall thickness of similar to 20 nm. The magnetic properties of ZnO/SnO2 nanotubes are studied using a superconductor quantum interference device (SQUID) magnetometer, and revealing the room-temperature ferromagnetism. The ferromagnetic origin has been ascribed to intrinsic defects. The coercivity and saturation magnetization of ZnO/SnO2 nanotubes at 5 K are estimated to be 191 Oe, 0.148 emu/g and higher than at 300 K. Such a ferromagnet without the presence of any transition metal could be a very good option for a class of spintronics.

Theoretical Simulations and Quantitative Magnetic Field Measurements for Eddy-Current Testing with an HTS SQUID System

The use of a Superconducting QUantum Interference Device (SQUID) magnetometer for quantitative measurements in eddy-current nondestructive evaluation is presented. The SQUID is used in absolute mode, and the magnetic field measurements are directly compared to theoretical results from both analytical and semi-analytical models. The measurements are taken in an ambient noise environment, and the excitation has the form of a double-rectangle printed-circuit-board coil. The configurations examined involve the coil in air and above aluminum plates with or without defects in the form of notches. Agreement between experimental and theoretical results is very good in all cases, showing that SQUID magnetometers can be used for quantitative magnetic field measurements and that modeling can be readily applied for parametric analysis and optimizations of the measurement configuration including excitation coils' design and frequency selection.

Swift Heavy Ion Induced Modification in Physical Properties of Poly Methylmethacrylate (PMMA)/Nickel (Ni) Nanocomposites

We have These films were irradiated with 85 MeV C-ions at the fluences of 1 x 1011 and 1 x 1012 ions/cm2. Changes in the optical, structural, dielectric, magnetic and thermal properties of (PMMA)/Ni nanocomposites of different concentrations of nickel nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of UVvisible spectroscopy, X-ray diffraction, impedance gain phase analyzer, SQUID and differential scanning calorimetry. Optical properties like band gap were estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength range 200-800 nm. It was found that the band gap value shifted to lower energy on doping with metal nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to the scissioning of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Surface morphology of the pristine and irradiated films was studied by scanning electron microscopy (SEM). The breakage of chemical bonds resulted in an increase of free radicals, unsaturation etc. as revealed from FTIR analysis. The dielectric properties were observed to enhance with an increase in metal compound concentration as well as with irradiation dose. This may be due to metal/polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. Zero-Field-Cooled (ZFC)/Field-Cooled (FC) magnetization and magnetic hysteresis measurements were performed using a superconducting quantum interference device (SQUID) magnetometer from temperatures ranging from 5 K to 300 K, to investigate the magnetic properties of nanocomposites. The changes in topography of surfaces were also observed upon irradiation.

Spin Wave Excitation in a Mechanically Alloyed Co2MnSi Solid Solution

The spin wave excitation has been analyzed in a Co2MnSi solid solution compound. A Co2MnSi sample was prepared by utilizing a mechanical alloying technique in Ar atmosphere. After 72 hours of milling time, the Co2MnSi solid solution was transformed from a multiphase to a single broadening phase, which is essential in understanding the spin wave excitation in a nanocrystalline material. The magnetization was measured from 7 K to room temperature by using a superconducting quantum interference device (SQUID) magnetometer. The thermal-magnetization curve was found to obey the Bloch law, M S(T)=M S(0)(1−BT 3/2−CT 5/2). Based on this formula, the spin wave stiffness constant was calculated from the magnetization data at low temperatures. The values were 0.264 eV⋅A2 and 0.325 eV⋅A2 for 72 and 96 hours of milling time, respectively. The spectroscopic splitting g-factor was obtained via electron spin resonance (ESR) measurements at X-band (9.45 GHz).

Synthesis and characterization of poly(ɛ-caprolactone)/Fe3o4 nanocomposites by in situ polymerization

A series of magnetic nanocomposites based on poly(ɛ-caprolactone) (PCL) and Fe3O4 nanoparticles were prepared using a facile in situ polymerization method. The chemical structures of the PCL/Fe3O4 nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Results of wide-angle X-ray diffraction (WAXD) showed that the incorporation of the Fe3O4 nanoparticles did not affect the crystallization structure of the PCL. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology and dispersion of the Fe3O4 nanoparticles within the as-synthesized nanocomposites. Results of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) showed that the crystallization temperature was raised and the spherulites size decreased by the presence of Fe3O4 nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. The thermal stability of the PCL was depressed by incorporation of Fe3O4 nanoparticles from thermogravimetric analysis (TGA). The superparamagnetic behavior of the PCL/Fe3O4 nanocomposites was testified by the superconducting quantum interference device (SQUID) magnetometer analysis. The obtained biodegradable nanocomposites will have a great potential in magnetic resonance imaging contrast and targeted drug delivery.