Spin configurations in a single Fe cube

Size-Specific Spin Configurations in Single Iron Nanomagnet: From Flower to Exotic Vortices.

Christophe Gatel, Francisco Javier Bonilla, Anca Meffre, Etienne Snoeck, Bénédicte Warot-Fonrose, Bruno Chaudret, Lise-Marie Lacroix, and Thomas Blon

Nano Letters 15, 6952 (2015)

From shape to surface effects in magnetic anisotropy of Co NPs

Size effects in the magnetic anisotropy of embedded cobalt nanoparticles: from shape to surface.
Simón Oyarzún, Alexandre Tamion, Florent Tournus, Véronique Dupuis, Matthias Hillenkamp

Scientific Reports 5, 14749 (2015)

Comparison of the experimental values for with the magnetic surface anisotropy calculated using the Néel model for different example cluster sizes and single facets added along the [100] (blue, lower curve) and [111] (green, upper curve) directions.

Iron Oxide NPs for Multimodal Imaging and Magnetoresponsive Therapy

Iron Oxide Based Nanoparticles for Multimodal Imaging and Magnetoresponsive Therapy.
Nohyun Lee, Dongwon Yoo, Daishun Ling, Mi Hyeon Cho, Taeghwan Hyeon, and Jinwoo Cheon 
Chem. Rev. 115, 10637 (2015)
 

Néel skyrmions in confined geometries

Degeneracies and fluctuations of Néel skyrmions in confined geometries.
Rick Keesman, A. O. Leonov, P. van Dieten, Stefan Buhrandt, G. T. Barkema, Lars Fritz, and R. A. Duine 
Phys. Rev. B 92, 134405 (2015)

Simulations snapshots of spin systems of size L×L=3 for different parameter values and temperatures with the parameter D/Jchosen such that the pitch length p=8. The periodic boundary is drawn as a red solid line and spin vectors are represented by colored arrows where the color scales linearly with the zˆ component of the vector to highlight spin texture

Exchange bias in molecular layers

Exchange bias and room-temperature magnetic order in molecular layers.

Manuel Gruber, Fatima Ibrahim, Samy Boukari, Hironari Isshiki, Loïc Joly, Moritz Peter, Michał Studniarek, Victor Da Costa, Hashim Jabbar, Vincent Davesne, Ufuk Halisdemir, Jinjie Chen, Jacek Arabski, Edwige Otero, Fadi Choueikani, Kai Chen, Philippe Ohresser, Wulf Wulfhekel, Fabrice Scheurer, Wolfgang Weber, Mebarek Alouani, Eric Beaurepaire & Martin Bowen

Nature Materials 14, 981 (2015)

Adsorption geometry and magnetic properties of the MnPc stacking on Co deduced from DFT calculations.

 

Nano Kirkendall Effect

Nano Kirkendall Effect Related to Nanocrystallinity of Metal Nanocrystals: Influence of the Outward.and Inward Atomic Diffusion on the Final Nanoparticle Structure.
Zhijie Yang, Nailiang Yang, and Marie-Paule Pileni
The Journal of Physical Chemistry C 119, 22249 (2015)

Domain wall formation in dipolar NP assemblies

Longitudinal domain wall formation in elongated assemblies of ferromagnetic nanoparticles.
Miriam Varón, Marco Beleggia, Jelena Jordanovic, Jakob Schiøtz, Takeshi Kasama, Victor F. Puntes & Cathrine Frandsen
Scientific Reports 5, 14536 (2015)

Simulation of the relaxed F-state (a–c) and the relaxed L-state (d–f) with increasing reverse fields of (a,d) 0 mT, (b,e) 35 mT, and (c,f) 50 mT. The colors denote the orientation of the magnetic moment (cf. the color wheel in Fig. 3). Panels on the right hand side indicate the net moment in the length direction over the widths of the assemblies.

 

Neel and Brownian relaxation in NPs by ac field

Mixed Brownian alignment and Néel rotations in superparamagnetic iron oxide nanoparticle suspensions driven by an ac field.

Saqlain A. Shah, Daniel B. Reeves, R. Matthew Ferguson, John B. Weaver, and Kannan M. Krishnan
Phys. Rev. B 92, 094438 (2015)

Comparison between simulation and experiment for nanoparticles either in either a frozen or melted state. Spectroscopy was performed with a 26-kHz, 31 mT/μ0 field. The log-normal distributions of particle diameter and anisotropy constant are shown on the right by number in a representative 1000-particle subsample.

 

Phase transitions in spin ice of macroscopic dimensions

Thermodynamic phase transitions in a frustrated magnetic metamaterial.
L. Anghinolfi, H. Luetkens, J. Perron, M. G. Flokstra, O. Sendetskyi, A. Suter, T. Prokscha, P. M. Derlet, S. L. Lee & L. J. Heyderman
Nature Communications 6, 8278 (2015) 

(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

Dynamically stabilized magnetic skyrmions

Dynamically stabilized magnetic skyrmions.

Y. Zhou, E. Iacocca, A. A. Awad, R. K. Dumas, F. C. Zhang, H. B. Braun and J. Åkerman
Nature Communications 6, 8193 (2015)

(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.

From core/shell to hollow Fe/γ-Fe2O3 NPs

From core/shell to hollow Fe/γ-Fe2O3 nanoparticles: evolution of the magnetic behavior.

Z Nemati, H Khurshid, J Alonso, M H Phan, P Mukherjee and H Srikanth

Nanotechnology 26, 405705 (2015)

Bright-field TEM images of the 12 nm Fe/γ-Fe₂O₃ (a) core/shell, (b) core/void/shell, and (c) hollow nanoparticles

Magnetic skyrmions beyond room temperature

A new class of chiral materials hosting magnetic skyrmions beyond room temperature.

Y. Tokunaga, X. Z. Yu, J. S. White, H. M. Rønnow, D. Morikawa, Y. Taguchi, Y. Tokura

Nature Communications 6, 7638 (2015) 

Lorentz transmission electron microscopy (LTEM) of skyrmion crystal.

Neel-type skyrmion lattice

Néel-type skyrmion lattice with confined orientation in the polar magnetic semiconductor GaV4S8.
I. Kézsmárki, S. Bordács, P. Milde, E. Neuber, L. M. Eng, J. S. White, H. M. Rønnow, C. D. Dewhurst, M. Mochizuki, K. Yanai, H. Nakamura, D. Ehlers, V. Tsurkan & A. Loidl

Nature Materials 14, 1116 (2015) 

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.

Spin patterns in the magnetic phases of GaV₄S₈.

Giant moving vortex mass

Giant moving vortex mass in thick magnetic nanodots.
K. Y. Guslienko, G. N. Kakazei, J. Ding, X. M. Liu & A. O. Adeyeye
Scientific Reports 5, 13881 (2015)

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.

EB in spin glass/ferromagnet bilayers

Cooling field and temperature dependent exchange bias in spin glass/ferromagnet bilayers.
W. B. Rui, Y. Hu, A. Du, B. You, M. W. Xiao, W. Zhang, S. M. Zhou, J. Du
Scientific Reports 5, 13640 (2015)

(a) The M-H hysteresis loops measured under H_FC = 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 H_FC = 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 H_E and H_C.

Domain wall motion driven by spin torque

Influence of uniaxial anisotropy on domain wall motion driven by spin torque.

P. Chureemart, R. F. L. Evans, I. D'Amico, and R. W. Chantrell

Phys. Rev. B 92, 054434 (2015)

(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 0.5MA/cm2.

Skyrmions in MnSi Nanowires

Stabilized Skyrmion Phase Detected in MnSi Nanowires by Dynamic Cantilever Magnetometry
A. Mehlin, F. Xue, D. Liang, H. F. Du, M. J. Stolt, S. Jin, M. L. Tian, and M. Poggio
Nano Letters 15, 4839 (2015)

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.

Hollow magnetite NPs for Li storage

Formation of Uniform Fe3O4 Hollow Spheres Organized by Ultrathin Nanosheets and Their Excellent Lithium Storage Properties.

Fei-Xiang Ma, Han Hu, Hao Bin Wu, Cheng-Yan Xu, Zhichuan Xu, Liang Zhen and Xiong Wen (David) Lou

Advanced Materials 27, 4097 (2015) 

Recent Advances in Higher-Order, Multimodal, Biomedical Imaging Agents

Recent Advances in Higher-Order, Multimodal, Biomedical Imaging Agents.

James Rieffel, Upendra Chitgupi and Jonathan F. Lovell
Small 35, 4445 (2015)

Size dependent magnetic hyperthermia

Size dependent magnetic hyperthermia of octahedral Fe3O4 nanoparticles.
Y. Lv, Y. Yang, J. Fang, H. Zhang, E. Peng, X. Liu, W. Xiao and J. Ding
RSC Advances 5, 76764 (2015)

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.

Photo-fluorescent and magnetic properties of iron oxide nanoparticles: Review

Photo-fluorescent and magnetic properties of iron oxide nanoparticles for biomedical applications.
Donglu Shi, M. E. Sadat, Andrew W. Dunna and David B. Mast
Nanoscale 7, 8209 (2015)

(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

Evolution of magnetism on a curved nano-surface - Nanoscale (RSC Publishing)

Evolution of magnetism on a curved nano-surface.

D. G. Merkel, D. Bessas, Z. Zolnai, R. Rüffer, A. I. Chumakov, H. Paddubrouskaya, C. Van Haesendonck, N. Nagy, A. L. Tóth and A. Deák

Nanoscale 7, 12878 (2015)

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.

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.

Recent Advances in Biomedical Imaging Agents

Recent Advances in Higher-Order, Multimodal, Biomedical Imaging Agents.

James Rieffel, Upendra Chitgupi andJonathan F. Lovell
Small 11, 4445 (2015)

γFe2O3@Au Magnetic Gold Nanoflowers for Efficient Cancer Theranostics

Rational Design and Synthesis of γFe2O3@Au Magnetic Gold Nanoflowers for Efficient Cancer Theranostics.

Jie Huang, Miao Guo, Hengte Ke, Cheng Zong, Bin Ren, Gang Liu, He Shen, Yufei Ma, Xiaoyong Wang, Hailu Zhang, Zongwu Deng, Huabing Chen and Zhijun Zhang

Adv. Materials 9, 5049 (2015) 

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

EB in molecular layers

Exchange bias and room-temperature magnetic order in molecular layers.

Manuel Gruber, Fatima Ibrahim, Samy Boukari, Hironari Isshiki, Loïc Joly, Moritz Peter, Michał Studniarek, Victor Da Costa, Hashim Jabbar, Vincent Davesne, Ufuk Halisdemir, Jinjie Chen, Jacek Arabski, Edwige Otero, Fadi Choueikani, Kai Chen, Philippe Ohresser, Wulf Wulfhekel, Fabrice Scheurer, Wolfgang Weber, Mebarek Alouani, Eric Beaurepaire, Martin Bowen

Nature Materials 14, 981 (2015)

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.