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| Radial distribution of the magnetic anisotropy parameters (dots) in the E plane in the case of NS=50 samples with N=225+25 atoms. The continuous line presents the predictions of the Gaussian orthogonal ensemble. Inset: Distribution of (K1,K2) in the E plane for these 50 nanograins. At this level of disorder the triangular structure is almost entirely lost. |
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(left) Schematic representation of the
inverse AFM/FiM core/shell structure and (right) hysteresis loops of the
doubly inverted nanoparticles, for different AFM core sizes (Dcore) and constant FiM shell thickness of four lattice spacings.
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One
current challenge of magnetic hyperthermia is achieving therapeutic
effects with a minimal amount of nanoparticles, for which improved
heating abilities are continuously pursued. However, it is demonstrated
here that the performance of magnetite nanocubes in a colloidal solution
is reduced by 84% when they are densely packed in three-dimensional
arrangements similar to those found in cell vesicles after nanoparticle
internalization. This result highlights the essential role played by the
nanoparticle arrangement in heating performance, uncontrolled in
applications. A strategy based on the elaboration of nano-objects able
to confine nanocubes in a fixed arrangement is thus considered here to
improve the level of control. The obtained specific absorption rate
results show that nanoworms and nanospheres with fixed one- and
two-dimensional nanocube arrangements, respectively, succeed in reducing
the loss of heating power upon agglomeration, suggesting a change in
the kind of nano-object to be used in magnetic hyperthermia.
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| Collapsed phase diagram for different scaling λ values. The inset shows the phase diagram for some selected scaling values, i.e., before the scaling up process. |
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a, Uncompensated magnetization, M, in Mn3−xPtxGa going through a compensation point (M = 0) at x
= 0.59 (upper panel): squares are results from theoretical
calculations. The line is a guide to eye. Lower panel: Experimental EB
field HEB at 4.2 K (solid circles). The solid line
corresponds to the result of our calculation. The regular and inverse
Heusler structures of the Mn3Ga and Mn2PtGa are shown to the left and right respectively. b–d, Magnetic moments of Mn in two different sublattices for Mn3Ga, Mn2.41Pt0.59Ga and Mn2PtGa.
Red arrows correspond to Mn in the Mn–Ga plane and blue arrows to Mn in
the Mn–Mn planes. The size and direction of the moment is indicated by
the arrow. Perfect magnetic compensation is expected in Mn2.41Pt0.59Ga. e, FM domains (boundaries indicated by dashed lines) inside the compensated AFM host.
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| Here, it is shown that binary superlattices of Co/Ag nanocrystals with the same size, surface coating, differing by their type of crystallinity are governed by Co–Co magnetic interactions. By using 9 nm amorphous-phase Co nanocrystals and 4 nm polycrystalline Ag nanocrystals at 25 °C, triangle-shaped NaCl-type binary nanocrystal superlattices are produced driven by the entropic force, maximizing the packing density. By contrast, using ferromagnetic 9 nm single domain (hcp) Co nanocrystals instead of amorphous-phase Co, dodecagonal quasicrystalline order is obtained |
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| Amplitude of the |A2|2 level in the two-parameter space (ε,a1−0.5), obtained from numerical solutions of Eqs. (14) and (15). Regions where |A2|2 is larger are those of efficient population transfer (i.e., efficient magnetization switching). |
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| (a) Rare-earth ions lattice in the pyrochlore R2M2O7 and normal spinel CdR2X4 compounds. The thicker light blue (thinner dark blue) bold line represents a 6 (10)-site loop. (b) Low-temperature heat capacity of CdHo2S4. |
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| Topography of mz during the skyrmion polarity switching process. The insets on the lower right show mz in the disk plane. The insets on the upper right display the cutlines along the diameter through the disk center. (i) Variation of the Rs with simulation time. |
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| Illustration of two magnetic modes in an antiferromagnetic nanoparticle with a vertical easy axis. The A (B) sublattice points in the +z(−z) direction and describes a blue (red) trajectory: (top) a uniform in-plane magnetic mode; the ωα mode; (bottom) the “rotor mode.” |
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| Imprinting non-collinear magnetic spin textures into out-of-plane magnetised films (Co/Pd multilayers) via interlayer coupling to a vortex state (Permalloy, Py) (a). Calculations are carried out for a Co/Pd anisotropy of Ku = 200 kJ/m3. Depending on the interlayer exchange coupling strength and the magnetic field treatment (remanence or relaxed state), configurations of distinct topology can be imprinted in the out-of-plane magnetised layer as revealed by micromagnetic simulations. Figures (b)–(e) show the magnetic configuration of four different states in Co/Pd films with decreasing strength of interlayer coupling Ji (left to right) after applying an out-of-plane magnetic field. Colours correspond to the normalised out-of-plane magnetisation component: (b) Remanent and relaxed vortex state; (c)–(d) remanent donut state type II and type I (number of domain walls), respectively; and (e) relaxed magnetic spiral. The skyrmion number S of each state is assessed based on the sketched magnetisation configuration in the cross-section. (f) Line profiles through the center of the Co/Pd film for the normalised out-of-plane magnetisation (mz = Mz/Ms) in remanent state Co/Pd spins illustrate the possibility to tailor the opening angle of the donut state by adjusting Ji. The magnetic spiral also appears after opening the circular domain wall of the donut state by applying a small in-plane magnetic field. |
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| Cobalt atoms exposed to hydrogen gas have higher spins, an effect that could be used to build magnetic nanostructures and lattices. |
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| Semilog plots of q̃2(t0,t) and q2 vs time t (in MC sweeps) for DIS systems with concentration x=0.35 running at the lowest temperature Tn for the values of L indicated in the figure. T=0.075(T=0.05) for L=10(L=8). |
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| AMR spectra measured on a disk shaped sample for (a) up (p=+1) and (b) down (p=−1) polarization of the vortex core for an excitation current of 1.2 mA. The sample design is shown in the inset of (a). By applying a rotating current (counterclockwise or clockwise) the VC polarity can be switched selectively to up or down. A sign change of the AMR voltage signal can be observed for the two polarities. Note that a significant shift of the resonance frequency to higher frequencies is observed at larger bias fields. Also note that the fine structure observed in the spectra does not depend on the VC polarity. |
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| Reduced ordered plus induced moment μ¯i≡μi/μsat versus reduced staggered magnetic field h†≡gμBH†/kBTN at the indicated reduced temperatures t≡T/TN for (a) spin S=1/2 and (b) spin S=7/2. |
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| Sketch of a quantum communication channel and properties of spins entangled through antiferromagnetic interactions |
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| Hysteresis loops for FeF2(70 nm)/NiFe (30 and 100 nm) bilayers at (a) T=10 and (b) T=70 K. Symbol: Experimental data. Blue solid line in (a): Simulation. |
