Defect-Engineering by Solvent Mediated Mild Oxidation as a Tool to Induce Exchange Bias in Metal Doped Ferrites.

The crystal site occupancy of different divalent ions and the induction of lattice defects represent an additional tool for modifying the intrinsic magnetic properties of spinel ferrites nanoparticles. Here, the relevance of the lattice defects is demonstrated in the appearance of exchange-bias and in the improvement of the magnetic properties of doped ferrites of 20 nm, obtained from the mild oxidation of core@shell (wüstite@ferrite) nanoparticles. Three types of nanoparticles (Fe0 O@Fe O , Co Fe O@Co Fe O and Ni Co Fe O@Ni Co Fe O ) are oxidized.

Spin-to-Charge Conversion in All-Oxide LaSrMnO/SrIrO Heterostructures.

Spin injection and spin-charge conversion processes in all-oxide LaSrMnO/SrIrO (LSMO/SIO) heterostructures with different SIO layer thickness and interfacial features have been studied. Ferromagnetic resonance (FMR) technique has been used to generate pure spin currents by spin pumping (SP) in ferromagnetic (FM) half-metallic LSMO. The change of the resonance linewidth in bare LSMO layers and LSMO/SIO heterostructures suggests a successful spin injection into the SIO layers.

Gel transformation as a general strategy for fabrication of highly porous multiscale MOF architectures.

The structure and chemistry of metal-organic frameworks or MOFs dictate their properties and functionalities. However, their architecture and form are essential for facilitating the transport of molecules, the flow of electrons, the conduction of heat, the transmission of light, and the propagation of force, which are vital in many applications. This work explores the transformation of inorganic gels into MOFs as a general strategy to construct complex porous MOF architectures at nano, micro, and millimeter length scales.

Spin Glass State in Strained LaCaMnO Thin Films.

Epitaxial strain modifies the physical properties of thin films deposited on single-crystal substrates. In a previous work, we demonstrated that in the case of LaCaMnO thin films the strain induced by the substrate can produce the segregation of a non-ferromagnetic layer (NFL) at the top surface of ferromagnetic epitaxial LaCaMnO for a critical value of the tetragonality τ, defined as = | - |, of τ ≈ 0.024.

3d Metal Doping of Core@Shell Wüstite@ferrite Nanoparticles as a Promising Route toward Room Temperature Exchange Bias Magnets.

Nanometric core@shell wüstite@ferrite (Fe O@Fe O ) has been extensively studied because of the emergence of exchange bias phenomena. Since their actual implementation in modern technologies is hampered by the low temperature at which bias is operating, the critical issue to be solved is to obtain exchange-coupled antiferromagnetic@ferrimagnetic nanoparticles (NPs) with ordering temperature close to 300 K by replacing the divalent iron with other transition-metal ions. Here, the effect of the combined substitution of Fe  with Co  and Ni  on the crystal structure and magnetic properties is studied.

Strong Crystallographic Influence on Spin Hall Mechanism in PLD-Grown IrO Thin Films.

Spin-to-charge conversion is a central process in the emerging field of spintronics. One of its main applications is the electrical detection of spin currents, and for this, the inverse spin Hall effect (ISHE) has become one of the preferred methods. We studied the thickness dependence of the ISHE in iridium oxide (IrO2) thin films, producing spin currents by means of the spin Seebeck effect in γ-Fe2O3/IrO2 bilayers prepared by pulsed laser deposition (PLD).

Simple Sonochemical Method to Optimize the Heating Efficiency of Magnetic Nanoparticles for Magnetic Fluid Hyperthermia.

We developed a fast, single-step sonochemical strategy for the green manufacturing of magnetite (FeO) magnetic nanoparticles (MNPs), using iron sulfate (FeSO) as the sole source of iron and sodium hydroxide (Na(OH)) as the reducing agent in an aqueous medium. The designed methodology reduces the environmental impact of toxic chemical compounds and minimizes the infrastructure requirements and reaction times down to minutes. The Na(OH) concentration has been varied to optimize the final size and magnetic properties of the MNPs and to minimize the amount of corrosive byproducts of the reaction.

Unraveling the mechanism of the one-pot synthesis of exchange coupled Co-based nano-heterostructures with a high energy product.

The development of reproducible protocols to synthesize hard/soft nano-heterostructures (NHSs) with tailored magnetic properties is a crucial step to define their potential application in a variety of technological areas. Thermal decomposition has proved to be an effective tool to prepare such systems, but it has been scarcely used so far for the synthesis of Co-based metal/ferrite NHSs, despite their intriguing physical properties. We found a new approach to prepare this kind of nanomaterial based on a simple one-pot thermal decomposition reaction of metal-oleate precursors in the high boiling solvent docosane.

Observation of unexpected uniaxial magnetic anisotropy in LaSrMnO films by a BaTiO overlayer in an artificial multiferroic bilayer.

We studied in detail the in-plane magnetic properties of heterostructures based on a ferroelectric BaTiO overlayer deposited on a ferromagnetic LaSrMnO film grown epitaxially on pseudocubic (001)-oriented SrTiO, (LaAlO)(SrTaAlO) and LaAlO substrates. In this configuration, the combination of both functional perovskites constitutes an artificial multiferroic system with potential applications in spintronic devices based on the magnetoelectric effect. LaSrMnO single layers and BaTiO/LaSrMnO bilayers using the pulsed-laser deposition technique.

Rapid and scalable production of high-quality phosphorene by plasma-liquid technology.

Scalable synthesis of few-layered phosphorene typically relies on liquid ultrasonic/shear exfoliation but this technique suffers from drawbacks such as the long processing time, small sheet size, and poor quality. Herein, a simple and efficient plasma-liquid technique for rapid (∼5 minutes) and scalable production of few-layered high-quality phosphorene has been described. The plasma-exfoliated phosphorene has a tunable thickness less than 10 nanometers and a large size over a micrometer, enabling the fabrication of a macroscopic photodetection device with good photo-response.

Long-range vortex transfer in superconducting nanowires.

Under high-enough values of perpendicularly-applied magnetic field and current, a type-II superconductor presents a finite resistance caused by the vortex motion driven by the Lorentz force. To recover the dissipation-free conduction state, strategies for minimizing vortex motion have been intensely studied in the last decades. However, the non-local vortex motion, arising in areas depleted of current, has been scarcely investigated despite its potential application for logic devices.

Real space manifestations of coherent screening in atomic scale Kondo lattices.

The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation.

Gold-decorated magnetic nanoparticles design for hyperthermia applications and as a potential platform for their surface-functionalization.

The integration of noble metal and magnetic nanoparticles with controlled structures that can couple various specific effects to the different nanocomposite in multifunctional nanosystems have been found interesting in the field of medicine. In this work, we show synthesis route to prepare small Au nanoparticles of sizes  = 3.9 ± 0.

The relevance of Brownian relaxation as power absorption mechanism in Magnetic Hyperthermia.

The Linear Response Theory (LRT) is a widely accepted framework to analyze the power absorption of magnetic nanoparticles for magnetic fluid hyperthermia. Its validity is restricted to low applied fields and/or to highly anisotropic magnetic nanoparticles. Here, we present a systematic experimental analysis and numerical calculations of the specific power absorption for highly anisotropic cobalt ferrite (CoFeO) magnetic nanoparticles with different average sizes and in different viscous media.

Controlling the dominant magnetic relaxation mechanisms for magnetic hyperthermia in bimagnetic core-shell nanoparticles.

We report a simple and effective way to control the heat generation of a magnetic colloid under alternate magnetic fields by changing the shell composition of bimagnetic core-shell Fe3O4/ZnxCo1-xFe2O4 nanoparticles. The core-shell structure constitutes a magnetically-coupled biphase system, with an effective anisotropy that can be tuned by the substitution of Co2+ by Zn2+ ions in the shell. Magnetic hyperthermia experiments of nanoparticles dispersed in hexane and butter oil showed that the magnetic relaxation is dominated by Brown relaxation mechanism in samples with higher anisotropy (i.

Structurally Oriented Nano-Sheets in Co Thin Films: Changing Their Anisotropic Physical Properties by Thermally-Induced Relaxation.

We show how nanocrystalline Co films formed by separated oblique nano-sheets display anisotropy in their resistivity, magnetization process, surface nano-morphology and optical transmission. After performing a heat treatment at 270 °C, these anisotropies decrease. This loss has been monitored measuring the resistivity as a function of temperature.

Cell damage produced by magnetic fluid hyperthermia on microglial BV2 cells.

We present evidence on the effects of exogenous heating by water bath (WB) and magnetic hyperthermia (MHT) on a glial micro-tumor phantom. To this, magnetic nanoparticles (MNPs) of 30-40 nm were designed to obtain particle sizes for maximum heating efficiency. The specific power absorption (SPA) values (f = 560 kHz, H = 23.

Chemical Disorder in Topological Insulators: A Route to Magnetism Tolerant Topological Surface States.

We show that the chemical inhomogeneity in ternary three-dimensional topological insulators preserves the topological spin texture of their surface states against a net surface magnetization. The spin texture is that of a Dirac cone with helical spin structure in the reciprocal space, which gives rise to spin-polarized and dissipation-less charge currents. Thanks to the nontrivial topology of the bulk electronic structure, this spin texture is robust against most types of surface defects.

Mn NMR observation of colossal magnetoresistance effect in SmSrMnO.

Temperature dependent Mn NMR study of SmSrMnO is reported. Previous bulk magnetization measurements have shown that below T ~ 125 K the sample is ferromagnetic metallic (FMM) and above T it is charge ordered and insulating. In present report, we show that from zero-field NMR a single line double-exchange (DE) signal is observed at temperatures up to 139 K, which is due to a presence of FMM clusters also above T .

Thickness-modulated tungsten-carbon superconducting nanostructures grown by focused ion beam induced deposition for vortex pinning up to high magnetic fields.

We report efficient vortex pinning in thickness-modulated tungsten-carbon-based (W-C) nanostructures grown by focused ion beam induced deposition (FIBID). By using FIBID, W-C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.

In Silico before In Vivo: how to Predict the Heating Efficiency of Magnetic Nanoparticles within the Intracellular Space.

This work aims to demonstrate the need for in silico design via numerical simulation to produce optimal FeO-based magnetic nanoparticles (MNPs) for magnetic hyperthermia by minimizing the impact of intracellular environments on heating efficiency. By including the relevant magnetic parameters, such as magnetic anisotropy and dipolar interactions, into a numerical model, the heating efficiency of as prepared colloids was preserved in the intracellular environment, providing the largest in vitro specific power absorption (SPA) values yet reported. Dipolar interactions due to intracellular agglomeration, which are included in the simulated SPA, were found to be the main cause of changes in the magnetic relaxation dynamics of MNPs under in vitro conditions.

Magnetic hyperthermia enhances cell toxicity with respect to exogenous heating.

Magnetic hyperthermia is a new type of cancer treatment designed for overcoming resistance to chemotherapy during the treatment of solid, inaccessible human tumors. The main challenge of this technology is increasing the local tumoral temperature with minimal side effects on the surrounding healthy tissue. This work consists of an in vitro study that compared the effect of hyperthermia in response to the application of exogenous heating (EHT) sources with the corresponding effect produced by magnetic hyperthermia (MHT) at the same target temperatures.

Epitaxial Stabilization of the Perovskite Phase in (Sr(1-x)Ba(x))MnO3 Thin Films.

A novel mechanism of ferroelectricity driven by off-centering magnetic Mn(4+) ions was proposed in (Sr1-xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1-xBax)MnO3 thin films, 0.

Observation of the strain induced magnetic phase segregation in manganite thin films.

Epitaxial strain alters the physical properties of thin films grown on single crystal substrates. Thin film oxides are particularly apt for strain engineering new functionalities in ferroic materials. In the case of La(2/3)Ca(1/3)MnO(3) (LCMO) thin films, here we show the first experimental images obtained by electron holography demonstrating that epitaxial strain induces the segregation of a flat and uniform nonferromagnetic layer with antiferromagnetic (AFM) character at the top surface of a ferromagnetic (FM) layer, the whole film being chemical and structurally homogeneous at room temperature.