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| Comparison between simulation and experiment for nanoparticles either in
either a frozen or melted state. Spectroscopy was performed with a
26-kHz, 31 mT/ |
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| (a) Scanning electron microscope (SEM) micrograph showing a small part of an artificial kagome spin ice array with nanomagnets arranged on a kagome lattice (indicated in red). The whole array extends over an area of 25 mm2 and comprises 109 nanomagnets. Thermally active over a wide range of temperatures, such a large system is able to emulate the thermodynamics characteristic of bulk systems. Scale bar, 170 nm. (b) Highlights the predicted magnetic phase transitions. Snapshots of possible spin configurations for each phase are included, with magnetic charges of opposite sign indicated in red and blue at the vertices |
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| (a) A bubble skyrmion stabilized by dipolar interactions which may exist as a left- or right-handed version. Its size typically exceeds that of skyrmions stabilized by DMI. (b,c) DMI stabilized skyrmions: (b) A chiral skyrmion as favoured in B20-type materials such as MnSi. (c) A hedgehog skyrmion as favoured by interfacial DMI.(d) Dynamically stabilized magnetic skyrmion which requires neither dipolar interactions nor DMI and which exhibits precession around the (vertical) easy-axis anisotropy. (e) For vanishing dipolar interactions (DDI), DMI and Oe fields, and in absence of damping, the skyrmion precesses uniformly and breathing disappears. |
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| Bright-field TEM images of the 12 nm Fe/γ-Fe2O3 (a) core/shell, (b) core/void/shell, and (c) hollow nanoparticles |
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Lorentz transmission electron microscopy (LTEM) of skyrmion crystal. |
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| a, In a Bloch-type skyrmion, the spins rotate in the tangential planes—that is, perpendicular to the radial directions—when moving from the core to the periphery. b, In a Néel-type skyrmion, the spins rotate in the radial planes from the core to the periphery. The cross-section of the vortex is also depicted in both cases. |
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| Spin patterns in the magnetic phases of GaV4S8. |
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| The frequency of the lowest vortex gyrotropic mode vs. dot thickness, ω0(L) 2p: red squares – the experimental data, blue solid line – the simulated frequencies, green solid line – the calculations according to Eq. (4) accounting vortex mass, black dashed line – calculations without accounting for the vortex mass. |
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| (a) The M-H hysteresis loops measured under HFC = 0.2 kOe and 50 kOe at T = 2 K for a Fe11Au89(50 nm)/FeNi(5 nm) sample, (b) the calculated M-H hysteresis loops under HFC = 0.2 kOe and 50 kOe at T = 2.6 K for the SG/FM bilayers, and the experimental (c) and calculated (d) cooling field dependences of low-temperature HE and HC. |
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| (Top) The time variation of domain wall displacement with different
current densities. (Bottom) The initial DW velocity as a function of
current density: The critical current density, minimum current density
required to move DW is |
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| Using dynamic cantilever magnetometry we measure an enhanced skyrmion lattice phase extending from around 29 K down to at least 0.4 K in single MnSi nanowires (NWs). Although recent experiments on two-dimensional thin films show that reduced dimensionality stabilizes the skyrmion phase, our results are surprising given that the NW dimensions are much larger than the skyrmion lattice constant. Furthermore, the stability of the phase depends on the orientation of the NWs with respect to the applied magnetic field, suggesting that an effective magnetic anisotropy, likely due to the large surface-to-volume ratio of these nanostructures, is responsible for the stabilization. The compatibility of our technique with nanometer-scale samples paves the way for future studies on the effect of confinement and surfaces on magnetic skyrmions. |
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| Magnetic nanoparticle hyperthermia is promising as a cancer therapeutic treatment. Shape and size are two crucial factors for the magnetic hyperthermia performance of nanoparticles. In this work, octahedral Fe3O4 nanoparticles with different sizes are successfully synthesized and their magnetic hyperthermia performances are investigated systematically in a gel suspension. The results suggest a wide size range (43–98 nm) for high SAR values (up to 2629 W g−1). The SAR values are verified by hysteresis loss measured in the gel suspension. This study demonstrates that octahedral Fe3O4 nanoparticles can serve as an excellent thermal seed for high performance magnetic hyperthermia cancer treatment. |
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| (a) Graphical representation of Brownian, Néel and effective relaxation times as a function of particle diameter for different values of anisotropy constant (K)4 and (b) representation of heating due to Néel and Brownian relaxations, and hysteresis loss |
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| The magnetic moment configuration calculated by micromagnetic simulation for (a) 28 Å, (b) 38 Å, (c) 42 Å and (d) 72 Å iron thicknesses on 400 nm diameter spheres. The blue color represents the magnitude of the z component while the red stands for the x–y in-plane component. The non-magnetic part of the iron layer is shown in gray. |
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| Magnetic moment configuration calculated by micromagnetic simulation for (a) 26 Å, (b) 34.5 Å, (c) 48.5 Å and (d) 70.5 Å evaporated iron thickness on 25 nm diameter spheres. The blue color represents the magnitude of the z component while the red stands for the x–y in-plane component. |
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| An γFe2O3@Au core/shell-type magnetic gold nanoflower-based theranostic nanoplatform is developed. It is integrated with ultrasensitive surface-enhanced Raman scattering imaging, high-resolution photoacoustics imaging, real-time magnetic resonance imaging, and photothermal therapy capabilities |
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| The red arrows represent the orientation of the spin moments. Note that the third layer dominantly exhibits a paramagnetic behaviour. The left inset represents the second-ML molecule on top of the semi-transparent first-ML molecule. The right inset shows the relative alignment of the second-ML molecule (semi-transparent) to the third-ML molecule. |
