Negative MR Research Articles

Evolution of anomalous Hall effect in ferromagnetic Weyl semimetal NbxZr1–xCo2Sn

Abstract Magnetic topological semimetal can host various topological non-trivial states leading to exotic novel transport properties. Here we report the systematic magneto-transport studies on the Heusler alloy Nb x Zr1−x Co2Sn considered as a ferromagnetic (FM) Weyl semimetal. The cusp anomaly of temperature-dependent resistivity and large isotropic negative magneto-resistivity (MR) emerge around the FM transition consistent with the theoretical half-metallic predictions. The prominent anomalous Hall effect (AHE) has the same behavior with the applied field along various crystal directions. The Nb doping introduces more disorder resulting in the enhancement of the upturn for the temperature-dependent resistivity in low temperatures. With Nb doping, the AHE exhibits systemic evolution with the Fermi level lifted. At the doping level of x = 0.25, the AHE mainly originates from the intrinsic contribution related to non-trivial topological Weyl states.

Unconventional magnetotransport properties of two-dimensional ferromagnet Fe5GeTe2

Two-dimensional (2D) van der Waals FexGeTe2 metallic ferromagnets have Curie temperature near or even higher than room temperature, showing great prospects in the field of spintronics. Here, we study the magnetotransport properties of Fe5GeTe2 nanoflakes. Multiple sign changes of angle-dependent magnetoresistance (ADMR) are observed with changing temperature or magnetic field. The high field-induced negative to positive MR transition in low temperatures (T < 50 K) and the temperature-induced sign reversal of anisotropic MR at T = 130 K are responsible for these exotic and complex characteristics of ADMR. In addition, the electron–magnon scattering induced negative MR exhibits abnormal nonmonotonic temperature dependence, which is related to the nonmonotonic variation of anomalous Hall resistance and the transition of the carrier types at T = 150 K. The exotic magnetotransport properties of Fe5GeTe2 revealed in this work may help pave the way for the practical application of this 2D magnetic material.

Intrinsic origin of room temperature ferromagnetic ordering in (In0.97-xCoxMg0.03)2O3 thin films

The (In0.97-xCoxMg0.03)2O3 films with different Co concentration are prepared using RF magnetron sputtering. The XRD and XPS measurements show that the films are highly oriented and both Co and Mg elements present valence state of +2. The EXAFS spectra show that only substitutional Co ions exist in the film with x = 0.02. However, the films with higher Co concentration (x > 0.02) form separate phases of substitutional Co and metallic Co clusters. All the films exhibit n-type conductivity and the carrier concentration firstly decreases and then increases with Co doping. The transport mechanisms are dominated using Mott variable range hopping at low temperature and Hard bandgap hopping at high temperature. The Co dopant can effectively alter the MR characters, which undergoes a clear transition from negative MR to positive MR. All the films exhibit room temperature ferromagnetic hysteresis loop. Clear increase of ferromagnetic hysteresis loop and saturation magnetic moment are observed due to the incorporation of Co ions. The ferromagnetism is ascribed to oxygen vacancies-induced bound magnetic polarizations. The relative percentage of substitutional Co ions decrease with Co doping, which leads to the decreasing of number of bound magnetic polarons induced by oxygen vacancies, and then weaken the Ms.

Single-crystal growth, structure and thermal transport properties of the metallic antiferromagnet Zintl-phase β-EuIn2As2.

Zintl-phase materials have attracted significant research interest owing to the interplay of magnetism and strong spin-orbit coupling, providing a prominent material platform for axion electrodynamics. Here, we report the single-crystal growth, structure, magnetic and electrical/thermal transport properties of the antiferromagnet layer Zintl-phase compound β-EuIn2As2. Importantly, the new layered structure of β-EuIn2As2, in rhombohedral (R3̄m) symmetry, contains triangular layers of Eu2+ ions. The in-plane resistivity ρ(H, T) measurements reveal metal behavior with an antiferromagnetic (AFM) transition (TN ∼ 23.5 K), which is consistent with the heat capacity Cp(H, T) and magnetic susceptibility χ(H, T) measurements. Negative MR was observed in the temperature range from 2 K to 20 K with a maximum MR ratio of 0.06. Unique 4f7J = S = 7/2 Eu2+ spins were supposed magnetically order along the c-axis. The Seebeck coefficient shows a maximum thermopower |Smax| of about 40 μV K-1. The kink around 23 K in the Seebeck coefficient originates from the effect of the antiferromagnetic phase on the electron band structure, while the pronounced thermal conductivity peak at around 10 K is attributed to the phonon-phonon Umklapp scattering. The results suggest that the Eu2+ spin arrangement plays an important role in the magnetic, electrical, and thermal transport properties in β-EuIn2As2, which might be helpful for future potential technical applications.

Negative magnetoresistance effect in Ba-doped layered double perovskite La2CuSnO6

The layered double perovskite La2-xBaxCuSnO6 (0.05 ≤ x ≤ 0.20) ceramics were synthesized successfully by solid-state reaction, and the crystal structure, transport and magnetic properties are investigated. It is found that the temperature-dependent resistivity ρ(T) shows a semiconductor behavior, which is related to magnetic ordering in two-dimensional CuO2 layers, and the MR effect exists in La2-xBaxCuSnO6. With decreasing the temperature, the MR effect changes from positive to negative, giving a positive maximum at Tmax (≈ TC) and showing a large negative MR effect at around 40 K with a value of about 20–30% under field H = ± 50 kOe. It is suggested that the negative MR effect in Ba-doped La2CuSnO6 is attributed to the field-induced suppression of in-plane spin-disorder scattering in CuO2 layers. A small amount of Ba doping can adjust the competition and synergy of the AFM and FM interactions through changing the tilt and distortion of CuO6 octahedrons, the in-plane Cu-O bond lengths, and the content of Jahn-Teller exciton Cu2+ ions, besides the stabilization of the La2CuSnO6 structure. The competition and synergy of the AFM and FM interactions CuO2 layers dominate the transport and magnetic properties of Ba-doped La2CuSnO6.

Investigation of magnetic properties and colossal magnetoresistance in nanocrystalline doped manganite

Here in, we report structural, magnetic, and magneto-transport properties of nanocrystalline La0.6Ag0.2Bi0.2MnO3 prepared using citrate sol–gel method. By using scanning and transmission electron microscopy measurements, the morphology and particle size of the sample have been confirmed. The Mn2p x-ray photoelectron spectroscopy spectra revealed the nanoparticles contained the coexistence of Mn3+ and Mn4+ ions with Mn3+/Mn4+ ratio of 2:1. Field-cooled and zero field-cooled magnetization protocols with temperature span of 5 K–300 K, confirm the paramagnetic (PM) to ferromagnetic (FM) phase transition at critical temperature, ∼ 146 K. The complete investigation of isothermal magnetization (), Arrott plots, and magnetocaloric effect as well as quantitative analysis of second-order phase transition has been studied. The criticality at the PM-FM transition was examined for the sample, and the obtained critical exponents were verified for their reliability through the utilization of the scaling hypothesis and Kouvel-Fisher plot. We observed a large magnetic entropy change (∼7 J-Kg−1K−1) at upon 5 T magnetic field strength. The renormalized magnetic entropy change plots are found to collapse onto a single curve, thus verifying the universality of the sample. Above the metal–insulator transitions the electrical resistivity shows a small polaron hopping conduction mechanism, however, at low temperatures scattering mechanism dominates and the whole range was explained by the universal percolation model. The colossal value of negative MR is found to be 88% at 168 K under an applied field strength of 2 T. As a result of our experimental data, we can grasp the intuitive understanding of magnetic as well as transport properties in Bi-doped manganite systems potential for magnetic sensors and spintronics applications.

Positive and negative magnetoresistance and charge transport anisotropy in RB12 (R - Ho, Er, Tm) antiferromagnets with dynamic charge stripes

Magnetization M and magnetoresistance Δρρ(H,T) (MR) were studied and MR analyzed quantitatively in the complicated low temperature Néel phase of RB12 (R - Ho, Er and Tm) antiferromagnets with structural (originating from cooperative Jahn-Teller effect) and electronic (coming from dynamic charge stripes) instabilities. It is shown, that well below the Néel field (HN) the magnetoresistance is determined by the concurrence of carriers' scattering by spin-density waves (leading to a linear positive contribution Δρρ(H) ∼ H) from one side, and by ferromagnetic nanoscale clusters (leading to a linear negative MR) from the other. The development of different kind instabilities in the critical region just below HN results into the emergence of an additional negative quadratic MR term, attributed to the carriers’ scattering on 4f-5d local electron density fluctuations. The anisotropy of both two linear and one quadratic MR components is analyzed in detail and compared for RB12 compounds with different magnetic structure.

Magnetic Relaxation Switching Assay Using IFNα-2b-Conjugated Superparamagnetic Nanoparticles for Anti-Interferon Antibody Detection

Type I interferons, particularly IFNα-2b, play essential roles in eliciting adaptive and innate immune responses, being implicated in the pathogenesis of various diseases, including cancer, and autoimmune and infectious diseases. Therefore, the development of a highly sensitive platform for analysis of either IFNα-2b or anti-IFNα-2b antibodies is of high importance to improve the diagnosis of various pathologies associated with the IFNα-2b disbalance. For evaluation of the anti-IFNα-2b antibody level, we have synthesized superparamagnetic iron oxide nanoparticles (SPIONs) coupled with the recombinant human IFNα-2b protein (SPIONs@IFNα-2b). Employing a magnetic relaxation switching assay (MRSw)-based nanosensor, we detected picomolar concentrations (0.36 pg/mL) of anti-INFα-2b antibodies. The high sensitivity of the real-time antibodies’ detection was ensured by the specificity of immune responses and the maintenance of resonance conditions for water spins by choosing a high-frequency filling of short radio-frequency pulses of the generator. The formation of a complex of the SPIONs@IFNα-2b nanoparticles with the anti-INFα-2b antibodies led to a cascade process of the formation of nanoparticle clusters, which was further enhanced by exposure to a strong (7.1 T) homogenous magnetic field. Obtained magnetic conjugates exhibited high negative MR contrast-enhancing properties (as shown by NMR studies) that were also preserved when particles were administered in vivo. Thus, we observed a 1.2-fold decrease of the T2 relaxation time in the liver following administration of magnetic conjugates as compared to the control. In conclusion, the developed MRSw assay based on SPIONs@IFNα-2b nanoparticles represents an alternative immunological probe for the estimation of anti-IFNα-2b antibodies that could be further employed in clinical studies.

Nonlinear current response and electric quantum oscillations in the Dirac semimetal Cd3As2

Chiral anomaly is a distinct quantum anomaly associated with chiral fermions in Dirac or Weyl semimetals. The use of negative magnetoresistance (negative MR) as a signature for this anomaly remains contentious, as trivial mechanisms such as current jetting and weak localization can also induce negative MR. In this study, we report a novel nonlinear behavior of the chiral anomaly in the longitudinal direction, which we observed by applying parallel current and magnetic field to the Dirac semimetal Cd3As2. This nonlinear characteristic peaks at an intermediate magnetic field of approximately 5 T, displaying a resistance-increasing property concomitant with strengthening of the current source. Through angle-dependence experiments, we were able to rule out trivial factors, such as thermal effects, geometric artifacts, and anisotropy. Furthermore, additional electric quantum oscillations were observed when the direct current (DC) was applied as high as 300 μA. Such an unusual phenomenon is ascribed to the formation of quantized levels due to Bloch oscillation in the high DC regime, suggesting that an oscillatory density distribution may arise as the electric field increases. The non-Ohmic electric quantum oscillations open a new avenue for exploring chiral anomaly and other nontrivial topological properties, which is also one of the salient features of nonequilibrium steady states in condensed matter physics.

Negative magnetoresistance in Dirac semimetal Cd3As2 with in-plane magnetic field perpendicular to current

Topological insulators and semimetals have exotic surface and bulk states with massless Dirac or Weyl fermions, demonstrating microscopic transport phenomenon based on relativistic theory. Chiral anomaly induced negative magnetoresistance (negative MR) under parallel magnetic field and current has been used as a probable evidence of Weyl fermions in recent years. Here we report a novel negative MR result with mutually perpendicular in-plane magnetic field and current in Cd3As2 nanowires. The negative MR has a considerable value of −16% around 1.5 K and could persist to room temperature of 300 K with value of −1%. The gate tuning and angle dependence of the negative MR demonstrate the mechanism of the observed negative MR is different from the chiral anomaly. Percolating current paths induced by charge puddles and disorder might be involved to produce such considerable negative MR. Our results indicate the negative MR effect in topological semimetals involves synergistic effects of many mechanisms besides chiral anomaly.

Coexistence of logarithmic and SdH quantum oscillations in ferromagnetic Cr-doped tellurium single crystals

We report the synthesis of transition-metal-doped ferromagnetic elemental single-crystal semiconductors with quantum oscillations using the physical vapor transport method. The 7.7 atom% Cr-doped Te crystals (Cr:Te) show ferromagnetism, butterfly-like negative magnetoresistance in the low temperature (<3.8 K) and low field (<0.15 T) region, and high Hall mobility, e.g. 1320 cm2 V−1 s−1 at 30 K and 350 cm2 V−1 s−1 at 300 K, implying that Cr:Te crystals are ferromagnetic elemental semiconductors. When B // [001] // I, the maximum negative MR is ∼−27% at T = 20 K and B = 8 T. In the low temperature semiconducting region, Cr:Te crystals show strong discrete scale invariance dominated logarithmic quantum oscillations when the direction of the magnetic field B is parallel to the [100] crystallographic direction (B // [100]) and show Landau quantization dominated Shubnikov-de Haas oscillations for B // [210] direction, which suggests the broken rotation symmetry of the Fermi pockets in the Cr:Te crystals. The findings of coexistence of multiple quantum oscillations and ferromagnetism in such an elemental quantum material may inspire more study of narrow bandgap semiconductors with ferromagnetism and quantum phenomena.

Evaluation of liver metastasis in patients with breast cancer: Comparison of single-phase abdominopelvic CT and multi-phase liver CT.

To compare the usefulness of multi-phase liver CT and single-phase abdominopelvic CT (APCT) in evaluating liver metastasis in newly diagnosed breast cancer patients. In this retrospective study, a total of 7621 newly diagnosed breast cancer patients (mean age, 49.7years ± 10.1; 7598 women) who underwent single-phase APCT (n = 5536) or multi-phase liver CT (n = 2085) for staging workup between January 2016 and June 2019 were included. The staging CTs were categorized as having no metastasis, probable metastasis, or indeterminate lesions. MRI referral rate (proportion of patients underwent additional liver MRI), negative MRI rate (patients without true hepatic metastasis / patients underwent liver MRI), true positive CT rate (patients with true metastasis / patients categorized as probable metastasis), true metastasis rate among CT indeterminate (patients with true metastasis / patients categorized as indeterminate lesions), and overall liver metastasis rate were compared between the two groups. Further, the radiation dose was recorded for every patient. The proportions of having no metastasis and indeterminate lesions on the results of CT interpretation were significantly different between the two groups (P = 0.006). However, the MRI referral rate, negative MR rate, true positive CT rate, true metastasis rate among CT indeterminate, and overall liver metastasis rate were not significantly different between the two groups. Radiation dose of multi-phase CT was three times higher than that of single-phase CT. Multi-phase liver CT has little benefit over single-phase APCT in assessing liver metastasis in patients with breast cancer.

Clinical, Imaging and Neurogenetic Features of Patients with Gliomatosis Cerebri Referred to a Tertiary Neuro-Oncology Centre.

Gliomatosis cerebri describes a rare growth pattern of diffusely infiltrating glioma. The treatment options are limited and clinical outcomes remain poor. To characterise this population of patients, we examined referrals to a specialist brain tumour centre. We analysed demographic data, presenting symptoms, imaging, histology and genetics, and survival in individuals referred to a multidisciplinary team meeting over a 10-year period. In total, 29 patients fulfilled the inclusion criteria with a median age of 64 years. The most common presenting symptoms were neuropsychiatric (31%), seizure (24%) or headache (21%). Of 20 patients with molecular data, 15 had IDH wild-type glioblastoma, with an IDH1 mutation most common in the remainder (5/20). The median length of survival from MDT referral to death was 48 weeks (IQR 23 to 70 weeks). Contrast enhancement patterns varied between and within tumours. In eight patients who had DSC perfusion studies, five (63%) had a measurable region of increased tumour perfusion with rCBV values ranging from 2.8 to 5.7. A minority of patients underwent MR spectroscopy with 2/3 (66.6%) false-negative results. Gliomatosis imaging, histological and genetic findings are heterogeneous. Advanced imaging, including MR perfusion, could identify biopsy targets. Negative MR spectroscopy does not exclude the diagnosis of glioma.

Peculiarity of magnetocaloric and magnetoresistance effects in Ni–Mn–Sn–Fe alloy with successive metamagnetic structural transitions

Magnetocaloric and magnetoresistance properties originated from a metamagnetic structural transition were investigated in a Fe-doped Ni46.8Mn38.1Sn11.6Fe3.5 alloy. After annealing, the alloy exhibited the intermartensite phase that contributed to the multiple abrupt magnetization and resistivity changes during heating process of martensite transformation. As a result, three successive magnetic entropy change ΔSM peaks of 10.7, 14.5 and 9.7 J/kg·K at temperatures 275, 279 and 285 K respectively were observed, which was responsible for a wide working temperature span ΔTFWHM of 273–287 K and thus a large effective refrigeration capacity RCeff of 98.1 J/kg under 5.0 T. At the same time, a large negative magnetoresistance MR (e.g. over 26.7% at 275 K) was also revealed during heating process under 5.0 T. Such multi-functional magnetocaloric and magnetoresistance effects render Ni–Mn–Sn–Fe alloys promising working materials for magnetic refrigerants, information storage and thermal magnetoelectricity conversions.

Spin transport in fully ferromagnetic p–n junctions

We systematically investigate the spin-dependent transport properties of fully ferromagnetic (Ga,Fe)Sb/GaSb/(In,Fe)Sb and (Ga,Fe)Sb/(In,Fe)As p–n junctions grown by low-temperature molecular beam epitaxy. The (Ga,Fe)Sb/GaSb/(In,Fe)Sb p–n junctions show high Curie temperature (170–310 K) and rectifying characteristics. The polarity and magnitude of magnetoresistance of the (Ga,Fe)Sb/GaSb/(In,Fe)Sb junctions strongly depend on the GaSb spacer thickness (t). Large positive magnetoresistance (MR, 58%) and negative MR (−1.6%) were observed at 3.7 K for the samples with t = 2 and 4 nm, respectively. When the n-type (In,Fe)Sb layer was replaced by the n-type (In,Fe)As, giant MR over 500% was observed, which can be explained by spin-valve and spin-splitting effects. Our results shed light on rich spin-transport physics observed in fully ferromagnetic p–n junctions.

Colossal Magnetoresistance in Ti Lightly Doped Cr2Se3 Single Crystals with a Layered Structure.

Stoichiometric Cr2Se3 single crystals are particular layer-structured antiferromagnets, which possess a noncollinear spin configuration, weak ferromagnetic moments, moderate magnetoresistance (MR ∼14.3%), and poor metallic conductivity below the antiferromagnetic phase transition. Here, we report an interesting >16 000% colossal magnetoresistance (CMR) effect in Ti (1.5 atomic percent) lightly doped Cr2Se3 single crystals. Such a CMR is approximately 1143 times larger than that of the stoichiometric Cr2Se3 crystals and is rarely observed in layered antiferromagnets and is attributed to the frustrated spin configuration. Moreover, the Ti doping not only dramatically changes the electronic conductivity of the Cr2Se3 crystal from a bad metal to a semiconductor with a gap of ∼15 meV but also induces a change in the magnetic anisotropy of the Cr2Se3 crystal from strong out-of-plane to weak in-plane. Further, magnetotransport measurements reveal that the low-field MR scales with the square of the reduced magnetization, which is a signature of CMR materials. The layered Ti:Cr2Se3 with the CMR effect could be used as two-dimensional (2D) heterostructure building blocks to provide colossal negative MR in spintronic devices.

Magnetic resonance imaging: Role on diagnosing all types of endolymphatic hydrops

This study utilized the recently advanced technique in MR imaging to establish its role on diagnosing all types of endolymphatic hydrops (EH). Twenty-two patients (26 ears) with clinical EH were admitted due to acute hearing loss and/or vertiginous attack. Each patient underwent an inner ear test battery comprising audiometry, cervical and ocular vestibular-evoked myogenic potential tests, and caloric test, followed by MR imaging for confirmation. Of the 22 clinical EH patients, 12 patients were referred to primary EH (Meniere's disease), 8 patients were secondary EH (including delayed EH in 5), and 2 patients were EH of embryopathic origin. MR imaging of 26 affected ears demonstrated EH in the cochlea only for 14 ears, in the utricle and saccule only for 1 ear, and in all three endorgans for 3 ears, accounting for a sensitivity of 69% (18/26). The 8 affected ears showing negative MR images were EH patients with hearing recovery 1, just after vertiginous attack 3, and chronic low-tone hearing loss 4. In contrast, 3 out of 18 unaffected ears demonstrated asymptomatic EH in the cochlea, representing a specificity of 83% (15/18). The sensitivity and specificity of MR imaging for confirming all types of EH were 69% and 83%, respectively. Although diagnostic criteria can identify primary and delayed EH, MR imaging may provide a supplementary tool for diagnosing secondary, embryopathic, or asymptomatic EH, if patients are not with hearing recovery, chronic low-tone hearing loss, or just after vertiginous attack.

Anomalous de-phasing of quantum coherence phenomenon in superconductor/topological insulator (NbN/Bi1.95Sb0.05Se3) heterostructure

The proximity-induced changes in magneto-transport properties of a topological insulator and a superconductor in an NbN/Bi1.95Sb0.05Se3 heterostructure are reported. Mechanically exfoliated single-crystal flake of Bi1.95Sb0.05Se3 topological insulator (TI) is partially covered with a ∼150 nm thick niobium nitride superconductor using DC magnetron sputtering. The temperature-dependent resistance, R(T) across the junction, shows double transitions at 11.5 K and 8 K, followed by the resistance upturn. MR on NbN covered region exhibit the typical BC2 behavior. At T < 20 K, the uncovered TI part exhibits weak anti-localization (WAL) for B < ± 1 T and a transition to negative MR at B > ± 3.5 T, while the junction shows only the WAL feature. As the temperature increases, the classical B2 dependence is retrieved on the TI and across the junction. The temperature coefficient of the phase coherence length obtained from the Hikami Larkin Nagaoka (HLN) analysis changes sign at the superconducting transition TC, evincing the de-phasing of the quantum coherence WAL phenomenon by the proximity of a superconductor. In contrast, the BC2 behavior of the superconductor is less affected by TI.

Frequency and Causes of False Negative Diffusion-Weighted Imaging in Acute Ischemic Stroke

Objective: The high sensitivity of diffusion-weighted magnetic resonance imaging (DWI MRI) has led to its frequent use in the diagnosis of acute ischemic stroke (AIS). However, false negative DWI MRI results have been obtained for some patients diagnosed with stroke, which led us to initiate this study. Our aim was to determine the prevalence of false negative DWI MRI scans and prevent the clinician from making a late diagnosis or misdiagnosis by relying on MRI results only.Methods: In a retrospective file screening conducted between February 2017- February 2019, after the patients hospitalized with a diagnosis of ischemic stroke who couldn't have an MRI or who were diagnosed with transient ischemic attack were excluded, the frequency of patients with a normal initial cranial DW MRI scan whose follow up scans revealed acute diffusion restriction was identified, and vascular anatomical localization of stroke was classified according to OCSP (Oxfordshire Community Stroke Project).Results: Of 235 patients admitted to our clinic with a diagnosis of ischemic stroke, 21 couldn't have a DWI MRI, and of 214 stroke patients who had a DWI MRI, 23 were admitted with a transient ischemic stroke attack. Of the remaining 191 patients, 14 had initially negative DWI MRI images but their clinical findings lasted longer than 24 hrs so they had a follow up MRI, which revealed an ischemic lesion in brain diffusion. In our clinic, the percentage of false negative diffusion MR images was 7.3% (14/191). The distribution of ischemia in the aforementioned 14 patients was as follows: 6 patients with posterior circulation ischemia (POCI), including 4 in brain stem and 2 in cerebellum, 2 patients with lacunar stroke (LACI), 5 patients with partial anterior circulation ischemia (PACI) and 1 patient with total anterior circulation ischemia (TACI).When the time of symptom onset was questioned, data could be derived from only 8 patients' files, and DWI MR images were obtained within the first 6 hours according to the onset of the symptoms.Conclusion: In acute stroke patients, if symptoms of the patient are consistent with stroke during physical examination, the diagnosis of stroke should not be automatically ruled out even if brain DWI MRI is negative. The decision of urgent thrombolytic or endovascular intervention that can be taken for eligible patients should not be overlooked based on false negative DWI MRI findings. With this study, we aim to help clinicians avoid misdiagnosis or delays in diagnosis.

Manganese Ferrite Nanoparticles Encapsulated into Vitamin E/Sphingomyelin Nanoemulsions as Contrast Agents for High-Sensitive Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) is one of the most powerful non-invasive imaging modalities used in clinics due to its great spatial resolution and excellent soft-tissue contrast, though still less sensitive than other techniques such as the nuclear imaging modalities. This lack of sensitivity can be improved with the use of contrast agents based on nanomaterials. In recent years, researchers have focused on the development of magnetic nanoparticles, given their role as enhancers of the contrast signal based on the magnetic resonance. Manganese ferrite nanoparticles stand out, given their high magnetic susceptibility and magnetic soft nature. Herein, 10nm MnFe2 O4 nanoparticles, functionalized with the natural antioxidant vitamin E (VitE-MFO) are encapsulated into simple, biodegradable and non-toxic nanoemulsions (NEs), by a reproducible one-step method obtaining stable 150nm-sized magnetic nanoemulsions (VitE-MFO-NEs). After encapsulation, the superparamagnetic properties of VitE-MFO are maintained and MR imaging studies reveal an extremely high transverse relaxivity for VitE-MFO-NEs (652.9×10-3 m-1 s-1 ), twofold higher than VitE-MFO value. Moreover, VitE-MFO-NEs show great in vivo biocompatibility and good signal in in vivo and ex vivo MRI, which indicates their great potential for biomedical imaging enhancing the negative MR contrast and significantly improving the sensitivity of MRI.