Duality of Iron Oxide Nanoparticles in Cancer Therapy

Duality of Iron Oxide Nanoparticles in Cancer Therapy: Amplification of Heating Efficiency by Magnetic Hyperthermia and Photothermal Bimodal Treatment.

Ana Espinosa, Riccardo Di Corato, Jelena Kolosnjaj-Tabi, Patrice Flaud, Teresa Pellegrino, and Claire Wilhelm
ACS Nano 10, 2436 (2016)

The pursuit of innovative, multifunctional, more efficient, and safer treatments is a major challenge in preclinical nanoparticle-mediated thermotherapeutic research. Here, we report that iron oxide nanoparticles have the dual capacity to act as both magnetic and photothermal agents. We further explore every key aspect of this magnetophotothermal approach, choosing iron oxide nanocubes for their high efficiency for the magnetic hyperthermia modality itself. In aqueous suspension, the nanocubes’ exposure to both: an alternating magnetic field and near-infrared laser irradiation (808 nm), defined as the DUAL-mode, amplifies the heating effect 2- to 5-fold by comparison with magnetic stimulation alone, yielding unprecedented heating powers (specific loss powers) up to 5000 W/g.

High-topological-number magnetic skyrmions

High-topological-number magnetic skyrmions and topologically protected dissipative structure.

Xichao Zhang, Yan Zhou, and Motohiko Ezawa
Phys. Rev. B 93, 024415 (2016)

Time evolution of the high-Q skyrmion (Q=2). (a) Time evolution of the total energy Etotal, the DMI energy EDMI, the topological number Q, the in-plane (mx,my) and out-of-plane mz components of magnetization averaged over the simulation area, and the dissipation functions W. A high-Q skyrmion with Q=2 is created nearly at t=0.38 ns. The DMI constant D=2 mJ m−2. The spin current density j=3×1012 A m−2. The external magnetic field Bz=250 mT. (b) Top views of the magnetization distributions mx,my, and mz of the FM nanodisk, the corresponding topological charge density distribution q, and the Rayleigh dissipation function W at selected times. The green circle indicates the spin current injection region. The nucleation of a high-Q skyrmion with Q=2 occurs nearly at t=0.38 ns, where the dissipation function spreads all over the FM nanodisk, implying that the spin wave propagates. The DMI is turned off at t=10 ns. It is remarkable that the high-Q skyrmion remains stable even if the DMI is switched off, which demonstrates the topological protection against the change of a variable, that is, the DMI.

Quantum Stoner-Wohlfarth Model

Quantum Stoner-Wohlfarth Model.
Takuya Hatomura, Bernard Barbara, and Seiji Miyashita

Phys. Rev. Lett. 116, 037203 (2016)
 

Beating observed after the SW point. The red line shows the fidelity $s_f$ and the green, blue, and orange lines show $⟨s_z⟩$, $⟨s_x⟩-1.5$, and $⟨s_y⟩-2.5$, where the parameters are $S=20$, $H_x=1$, $D=1$, and $v=0.08$.

Colloidal Dimers on a Honeycomb Magnetic Lattice

Geometric Frustration of Colloidal Dimers on a Honeycomb Magnetic Lattice. 
Pietro Tierno
Phys. Rev. Lett. 116, 038303 (2016)

(a) Schematic of the FGF film with a magnetic bubble lattice subjected to an external field Hz. One Wigner-Seitz unit cell is shaded in blue with one paramagnetic colloid. For Hz=0, the lattice constant is a=11.6  μm and the radius R=4.2  μm. (b) Normalized distance r/a of one paramagnetic colloid from the center of a magnetic bubble versus Hz. (c) Normalized energy landscape for a FGF under a static field Hz=0.17Ms. The inset shows a 3D view of one triangular minimum. (d) Snapshots of a small section (48×42  μm2) of a magnetic bubble lattice filled with n=1, 2, 3 particles per pinning site (scale bar is 10  μm). Schematics at the bottom show the corresponding configurations in a triangular minimum.

Protein complexes: A candidate magnetoreceptor

A magnetic protein biocompass.

Siying Qin, Hang Yin, Celi Yang, Yunfeng Dou, Zhongmin Liu, Peng Zhang, He Yu, Yulong Huang, Jing Feng, Junfeng Hao, Jia Hao, Lizong Deng, Xiyun Yan, Xiaoli Dong, Zhongxian Zhao, Taijiao Jiang, Hong-Wei Wang, Shu-Jin Luo ; Can Xie

Nature Materials 15, 217 (2016)

a, A nanoscale Cry/MagR magnetosensor complex with intrinsic magnetic polarity acts as a light-dependent biocompass. Linear polymerization of Fe–S cluster-containing magnetoreceptors (MagR) leads to the formation of a rod-like biocompass at the centre (core, yellow), surrounded by photoreceptive cryptochromes (Cry; outer layer, cyan). b, Cross-section of a, indicating that electron transportation from the FAD group in Cry to the Fe–S cluster in MagR upon light stimulation may be possible. c, The biocompass model of magnetoreception. In animal navigation systems, the Cry/MagR magnetosensor complex may act as a biological compass that perceives information from the Earth’s geomagnetic field, such as polarity (as with a conventional compass), intensity and inclination. The surface representation of the Cry/MagR structure (cyan and yellow) has been validated by EM in this study (Figs 2 and 3). The intrinsic magnetic moment of the magnetosensor may form a polarity compass for the sensing of directional information from the Earth’s geomagnetic field. The capability to detect the intensity and the spontaneous alignment of the magnetosensor in magnetic fields (as shown on the left-hand side, and further elucidated in Fig. 5a, b), may form the basis of an intensity sensor and inclination compass. Earth’s magnetic poles (black arrows) are offset from the axis of rotation (black line). The inclination angle (labelled as ‘I’) and intensity of the field are indicated by the direction and length of the arrows (red in the Northern Hemisphere and blue in the Southern Hemisphere). MagR and Cry/MagR magnetosensors from two species, monarch butterfly (Danaus plexippus, upper right) and pigeon (Columba livia, lower right), were tested in this study, highlighting the evolutionarily conserved biocompass model.

Protein complexes: A candidate magnetoreceptor.

Kenneth J. Lohmann

Nature Materials 15, 136 (2016)

Photoreceptive cryptochromes (Cry) surround, in a helical fashion, a chain of magnetoreceptors (MagR) containing Fe–S clusters. Red arrows denote magnetic field lines.

Colloidal magnetic nanocrystal clusters: Review

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages.

Athanasia Kostopoulou, Alexandros Lappas

Nanotechnology Reviews 4, 595(2015)

Scheme summarizing common parameters, including, size and shape [surfaces] anisotropies, as well as exchange [interfaces] and dipolar [particle clustering] interactions. Each one of them alone or in synergy with one another may act in favor of enhanced magnetic properties (M_S, H_C) for surface-stabilized nanoscale structures. Nanoclusters may provide a modular carrier engineered to combine all such parameters for the benefit of their emerging application-specific tasks, for example, such as those required for contrast generation (r₂) in magnetic resonance imaging (MRI) and heat dissipation (SLP) in magnetic hyperthermia.

Skyrmions in chiral magnets with Rashba and Dresselhaus spin-orbit coupling

Skyrmions in chiral magnets with Rashba and Dresselhaus spin-orbit coupling.
James Rowland, Sumilan Banerjee, and Mohit Randeria
Phys. Rev. B 93, 020404 (2016)

Phase diagrams as a function of $AJ/D^2$ and $HJ/D^2$ for four values of $D_{\perp }/D_{\parallel }$. Easy-axis anisotropy corresponds to $A<0$ while easy-plane anisotropy to $A>0$. The cone, elliptic cone, and tilted FM phases are shown schematically, with the $Q$ vector shown in red and the texture traced out by spins shown in black.

Dipolar Interactions and Size Distribution on Blocking Temperature NPs

Role of Dipolar Interactions and Volume Particle Size Distribution on the Nonmonotonic Magnetic Field Dependence of the Blocking Temperature in Magnetic Nanoparticles.
Sueli H. Masunaga, Renato F. Jardim, Marcos J. Correia, and Wagner Figueiredo
J. Phys. Chem. C 120, 765 (2016)

The nonmonotonic behavior of the magnetic field dependence H of the superparamagnetic blocking temperature T_B(H) (or T_max(H)) of an assembly of magnetic nanoparticles NPs was studied both experimentally and theoretically. We have combined the measurements of zero-field cooling ZFC magnetization curves under H performed on samples with increasing concentration of Ni nanoparticles and Monte Carlo simulations. As a result, we have found that increasing the strength of the dipolar interaction between granules and the occurrence of a very narrow width of a log-normal volume particle size distribution of the NPs suppress the nonmonotonic behavior of T_max(H).

Vortex core in a single NP

Switching the Magnetic Vortex Core in a Single Nanoparticle.
Elena Pinilla-Cienfuegos, Samuel Mañas-Valero, Alicia Forment-Aliaga, and Eugenio Coronado
ACS Nano 10, 1764 (2016)

Here we report the experimental observation of the vortex state formation and annihilation in individual 25 nm molecular-based magnetic nanoparticles measured by low-temperature variable-field magnetic force microscopy. Interestingly, in these nanoparticles the switching of the vortex core can be induced with very small values of the applied static magnetic field.

Dipole interactions in crystals

Magnetic dipole interactions in crystals
David C. Johnston
Phys. Rev. B 93, 014421 (2016)

Eigenvalues (a) ${\lambda }_{(1/2,0,1/2)}$ for AFM wave vector k = (1/2,0,1/2)  r.l.u. and (b) ${\lambda }_{(1/2,1/2,1/2)}$ for AFM wave vector k = (1/2,1/2,1/2)  r.l.u. versus the $c/a$ ratio for a simple tetragonal lattice with the moments aligned along [010] ($b$ axis, solid red circles), [001] ($c$ axis, solid green diamonds), and [100] ($a$ axis, solid blue squares).

 

DM anisotropy in nanomagnets with in-plane magnetization

Dzyaloshinskii-Moriya anisotropy in nanomagnets with in-plane magnetization.
M. Cubukcu, J. Sampaio, K. Bouzehouane, D. Apalkov, A. V. Khvalkovskiy, V. Cros, and N. Reyren
Phys. Rev. B 93, 020401(R) (2016)

DMI-induced anisotropy orthogonal to the shape anisotropy as observed by MFM and simulations. All scale bars are 200 nm long. The arrows indicate the mean magnetization. (a) Experimental MFM phase images are displayed. The actual topographical shape is indicated by a dotted line. The MFM phase is coded in the same way as in Fig. 1. The approximate sizes are 730×260,250×100, and 160×50 nm2. (b) Corresponding simulations for different D values (all the other micromagnetic parameters fixed), using an ideal dipolar MFM tip 30 nm above the magnetic layer. The observations of the magnetization direction in ellipses of different shapes (but same materials) allow constraining the Dzyaloshinskii-Moriya interaction strength D: The shadings indicate the D values compatible with observations. In the intermediate case, the magnetization does not align along one of the axes, reflecting the minute energy difference between the states with different magnetization directions. (c) Map of the DMI and exchange energy densities (darker means lower energy density) for the case D=2.1 mJ/m2. The energy gain concentrates close to the edges.

 

Guiding Spin Spirals by Strain

Guiding Spin Spirals by Local Uniaxial Strain Relief.

Pin-Jui Hsu, Aurore Finco, Lorenz Schmidt, André Kubetzka, Kirsten von Bergmann, and Roland Wiesendanger

Phys. Rev. Lett. 116, 017201 (2016)

(a) Overview SP-STM topography image of the spin spiral in the Fe DL and the nanoskyrmion lattice in the Fe ML; the zigzag shape of the spin spiral wave fronts with an angle of θ∼154° is indicated (measurement parameters: U=+1.0  V, I=1  nA, T=4.8  K). (b) Sketch of the magnetic state of the reconstructed Fe DL, as deduced from the SP-STM measurements. (c),(d) SP-STM topography images of the zigzag spin spiral measured with an out-of-plane and in-plane spin-sensitive tip, respectively. The corresponding SP-STM simulations are in the insets

Refrustration and competing orders in spin ice

Refrustration and competing orders in the prototypical Dy2Ti2O7 spin ice material.

P. Henelius, T. Lin, M. Enjalran, Z. Hao, J. G. Rau, J. Altosaar, F. Flicker, T. Yavors'kii, and M. J. P. Gingras

Phys. Rev. B 93, 024402 (2016)

Set of interacting neighbors on the pyrochlore lattice. The first- (J1), second- (J2), and two distinct third- (J3a and J3b) nearest-neighbor pathways are indicated by red, blue, green, and orange connections, respectively, on the pyrochlore lattice of corner-sharing tetrahedra. A two-in/two-out state of two spins pointing into the center of the tetrahedron and two spins pointing out from the tetrahedron is shown in the upper-right-hand corner of the lattice. An ice-rule obeying state is characterized by all tetrahedra being in a two-in/two-out spin configuration, but with no other constraint on the orientation of the spins.