Wednesday 29 February 2012

Review on Domain wall nanoelectronics

Domain wall nanoelectronics.
G. Catalan, J. Seidel, R. Ramesh, J. F. Scott
Rev. Mod. Phys. 84, 119 (2012)
Ferroelectric ‘‘closure stripes’’ predicted by atomistic simulations of ultrathin films.

Tuesday 28 February 2012

Simulations of spin models on GPUs

Some recent articles reporting the implementation of Monte Carlo simulations on GPUs:

GPU-based Swendsen–Wang multi-cluster algorithm for the simulation of two-dimensional classical spin systems.
Yukihiro Komura, Yutaka Okabe

http://www.sciencedirect.com/science/article/pii/S001046551200032X
 
Simulating spin models on GPU
Martin Weigel
http://dx.doi.org/10.1016/j.cpc.2010.10.031

GPU accelerated Monte Carlo simulations of lattice spin models
M. Weigel, T. Yavors’kii
Physics Procedia 15 (2011) 92–96

Benchmarking GPU and CPU codes for Heisenberg spin glass over-relaxation
M. Bernaschi , G. Parisi , L. Parisi
Computer Physics Communications 182 (2011) 1265–1271

Simulating Lattice Spin Models on Graphics Processing Units
Tal Levy, Guy Cohen, and Eran Rabani
J. Chem. Theory Comput. 2010, 6, 3293–3301

Multi-GPU accelerated multi-spin Monte Carlo simulations of the 2D Ising model ✩
Benjamin Block, Peter Virnau, Tobias Preis
Computer Physics Communications 181 (2010) 1549–1556

GPU accelerated Monte Carlo simulation of the 2D and 3D Ising model q
Tobias Preis, Peter Virnau, Wolfgang Paul, Johannes J. Schneider
Journal of Computational Physics 228 (2009) 4468

http://www.tobiaspreis.de/gpgpu.html

Prediction of magnetic arrays

On thermalization of magnetic nano-arrays at fabrication. Cristiano Nisoli
New J. Phys. 14 035017 (2012)

Left: arrays of different lattice constants grown at the same fabrication temperature show an ordered microstate when the lattice constant is smaller than a critical value ac. In the figure we plot the blocking temperature Tb(h) and the critical temperatures Tc(h) for arrays of three different values of the lattice constant (a > ac, a < ac, a = ac (this last one in red)) as a function of the height of the nano-islands h. h* is the stopping height, after which Tb >  T and therefore freezing-in starts.Right: during the fabrication of arrays of equal lattice constant the microstate can be controlled by varying the temperature T at deposition.

Low energy dynamics of ordered spin ice

Spin dynamics in the ordered spin ice Tb2Sn2O7.
Sylvain Petit, Pierre Bonville, Isabelle Mirebeau, Hannu Mutka, and Julien Robert
Phys. Rev. B 85, 054428 (2012)
Map of the powder average S(Q,ω) in Tb2Sn2O7 measured (left column) at 1.3 K (top) and 65 mK (middle), and calculated (right column)

Giant EB in multiferroics

Giant exchange bias in a nanocomposite of BiFeO3-Bi2Fe4O9
Tuhin Maity and Saibal Roy, Sudipta Goswami and Dipten Bhattacharya
ArXiv 1202.5898 (2012)
(a) The spontaneous exchange bias observed at different temperatures under zero-field cooling (b) the conventional EB observed under magnetic annealing at 5 K; it turns out to be negative in this case too

Dipolarly coupled vortex oscillators

Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillators.
A.D. Belanovsky, N. Locatelli, P.N. Skirdkov, F. Abreu Araujo, J. Grollier, K.A. Zvezdin, V. Cros, and A.K. Zvezdin
ArXiv 1202.5499 (2012)
Schematic representation of two inter-acting spin-transfer oscillators. Each pillar is composed by a free magnetic layers with vortex, a non magnetic spacer, and a SAF polarizer. Red arrows indicates the direction of spin polarization created by the polarizer. The nanopillars have a diameter D = 200 nm and are separated by a distance L. The parameters X1 and X2 define the cores positions.

Fe magnetic moment a MgO interface

Interfacial geometry dependence of the iron magnetic moment: The case of MgO/Fe/MgO.
Juan Ignacio Beltrán, Lluis Balcells, and Carlos Martínez-Boubeta
Phys. Rev. B 85, 064417 (2012)
Magnetic moment averaged per Fe atom from SQUID measurements (black circles), together with theoretical calculations of MgO/Fe/MgO structures with symmetric Fe-O bonding (green diamonds), and asymmetric coordination (blue triangles), as a function of the Fe thickness. The experimental data are fitted to a phenomenological exponential decaying function (as
mm = mmbulk + mmsurface e[1−thickness]/k, with the characteristic decay length k = 6 ML), which converge at large coverage to bulk Fe values.

Monday 27 February 2012

Modeling antidots arrays

Micromagnetic modelling of the anisotropy properties of permalloy antidot arrays with hexagonal symmetry.
A Manzin and O Bottauscio
J. Phys. D 45, 095001 (2012)
Magnetic domain configurations at remanent state for an antidot film with hole diameter d = 200 nm and centre-to-centre
nearest-neighbour hole distance T = 500 nm, considering (a) β = 0◦ and (b) β = 90◦.

Saturday 25 February 2012

Finite-size effects and charge ordering suppresion on manganite NPs

Particle-size effects on the suppression of charge ordering in Nd0.8Na0.2MnO3
B. Samantaray, S. K. Srivastava, and S. Ravi
J. Appl. Phys. 111, 013919 (2012)
The phase diagrams of Nd0.8Na0.2MnO3 for (a) D=700-nm, (b) D=250-nm, and (c) D=140-nm particle-size samples
obtained from magnetization measurements. Open and closed circles represent the threshold fields HC1 and HC2, respectively, and stars represent HS values.

Friday 24 February 2012

Quantum magnetism of individual Mn12 cluster

The Quantum Magnetism of Individual Manganese-12-Acetate Molecular Magnets Anchored at Surfaces
Steffen Kahle, Zhitao Deng, Nikola Malinowski, Charlène Tonnoir, Alicia Forment-Aliaga, Nicha Thontasen, Gordon Rinke, Duy Le, Volodymyr Turkowski, Talat S. Rahman,Stephan Rauschenbach, Markus Ternes, and Klaus Kern
Nano Letters 12, 518 (2012)
Here we demonstrate that electrospray ion beam deposition facilitates grafting of intact Mn12 molecules on metal as well as ultrathin insulating surfaces enabling submolecular resolution imaging by scanning tunneling microscopy. Using scanning tunneling spectroscopy we detect spin excitations from the magnetic ground state of the molecule at an ultrathin boron nitride decoupling layer. Our results are supported by density functional theory based calculations and establish that individual Mn12 molecules retain their intrinsic spin on a well chosen solid support.

Molecular magnet networks in all dimensions

Dimensionality Selection in a Molecule-Based Magnet.
Paul A. Goddard, Jamie L. Manson, John Singleton, Isabel Franke,1 Tom Lancaster, Andrew J. Steele,Stephen J. Blundell, Christopher Baines, Francis L. Pratt, Ross D. McDonald, Oscar E. Ayala-Valenzuela,Jordan F. Corbey, Heather I. Southerland, Pinaki Sengupta, and John A. Schlueter
Phys. Rev. Lett. 108, 077208 (2012)
(a) Normalized pulsed-field magnetization of planar (T = 1.5 K), and chainlike  (T =0:5 K) Mn12 compunds. (b) The results of QMC simulations of the low-temperature magnetization for 3D  2D and 1D AF. The lines are the pulsed-field data scaled by the saturation field (Bc). (c) The relation between the exchange anisotropy and the ratio of critical temperature and primaryexchange energy in Q1D and Q2D antiferromagnets deduced from QMC simulations (d) Anisotropy of the g factor in the planar and (e) chainlike compounds measured using ESR at 10 K and 1.5 K, respectively.

Improving biomedical applications of Fe oxide NPs

Ultrasmall Iron Oxide Nanoparticles for Biomedical Applications: Improving the Colloidal and Magnetic Properties.
Rocio Costo, Valentina Bello, Caroline Robic, Marc Port, Jose F. Marco, M. Puerto Morales, and
Sabino Veintemillas-Verdaguer
Langmuir 28, 178 (2012)
A considerable increase in the saturation magnetization, Ms (40%), and initial susceptibility of ultrasmall (<5 nm) iron oxide nanoparticles prepared by laser pyrolysis was obtained through an optimized acid treatment. Moreover, a significant enhancement in the colloidal properties, such as smaller aggregate sizes in aqueous media and increased surface charge densities, was found after this chemical protocol. The results are consistent with a reduction in nanoparticle surface disorder induced by a dissolution–recrystallization mechanism.

Ferroelectric solid state memories

Solid-state memories based on ferroelectric tunnel junctions.
André Chanthbouala, Arnaud Crassous, Vincent Garcia, Karim Bouzehouane, Stéphane Fusil, Xavier Moya, Julie Allibe, Bruno Dlubak, Julie Grollier, Stéphane Xavier, Cyrile Deranlot, Amir Moshar, Roger Proksch, Neil D. Mathur, Manuel Bibes and Agnés Barthélémy
Nature Nanotechn. 7, 101 (2012)
Ferroelectric switching versus resistive switching. a,b, Out-ofplane PFM phase (a) and amplitude (b) measurements on a typical gold/cobalt/BTO/LSMO ferroelectric tunnel junction. c, R(Vwrite) for a similar capacitor measured in remanence (Vread¼100 mV) after applying successive voltage pulses of 100 ms. The open and filled circles represent two different scans to show reproducibility.

Nanoelectronics: Ferroelectric devices show potential.
Adrian M. Ionescu
Nature Nanotechn. 7, 83 (2012)
The ferroelectric tunnel junction as a non-volatile memory cell.

Temperature dependence of Magnetite anisotropy

Magnetocrystalline anisotropy of magnetite.
R Reznıcek, V Chlan, H Stepankova, P Novak and M Marysko
J. Phys. CM 24, 055501 (2012)

Co nanopeapods

Fabrication of Nanopeapods: Scrolling of Niobate Nanosheets for Magnetic Nanoparticle Chain Encapsulation.
Yuan Yao, Girija S. Chaubey, and John B. Wiley
JACS 134, 2450 (2012)
Proposed mechanism for the formation of a nanopeapod. (a) Co NPs nucleate and grow in solution. (b) NPs assemble and form a chain on the surface of a niobateNS. (c, d) The niobate NS scrolls around the chain. (e) Nanopeapods form and separate from the niobate NSs.

Plasmon bleaching in Au/FeO dumbbells

Plasmon Bleaching Dynamics in Colloidal Gold−Iron Oxide Nanocrystal Heterodimers.
Alberto Comin, Kseniya Korobchevskaya, Chandramohan George, Alberto Diaspro, and Liberato Manna
Nano Letters 12, 921 (2012)
Transient absorption spectrum, measured at 110 μJ/cm2, of gold only and gold/FeO nanocrystals with, overlaid, three black traces corresponding to the positions of the maxima and of the zeros.

Thursday 23 February 2012

Finite-size effects on manganite NPs

Nanometer Size Effect on Magnetic Properties of Sm0.8Ca0.2MnO3 Nanoparticles.
Vladimir Markovich, Ivan Fita, Andrzej Wisniewski, Roman Puzniak, Dmitrii Mogilyansky, Przemyslaw Iwanowski, Piotr Dluzewski, and Gad Gorodetsky
J. Phys. Chem. C 116, 435 (2012)
(a,b) Magnetic field dependences of magnetization of SCMO23 and SCMO100 samples at T = 10 K measured after FC. Insets show a low field part of hysteresis loops on the extended scale. (c) Size dependence of spontaneous magnetization M0 and magnetization MS in H = 15 kOe at T = 10 K. (d) Coercive field of SCMO samples as a function of the particle size. Solid line is linear fit to the expression HC = a + b/D.

Oedering in Kagomé and squared spins ice

Multi-step ordering in kagome and square artificial spin ice.
C J Olson Reichhardt, A Libál and C Reichhardt
New Journal of Physics 14, 025006 (2012)
Black circles: particle locations; open ellipses: trap locations for a 20a0 ×20a0 section of a kagome ice sample. Colored circles indicate vertex types: N0 (blue), N1 (green), N2 (yellow) and N3 (red). (a) The positive biased ice-rule-obeying state. (b) The monopole state consisting of an ordered lattice of N0 and N3 vertices. (c) A finite-temperature ice-rule-obeying nonbiased state. (d) A high-temperature paramagnetic state where the vertex types are uncorrelated.

Core/Shell cobaltate NPs and low field MR

Low-Field Magnetoresistance Effect in Core–Shell Structured La 0.7 Sr 0.3 CoO 3 Nanoparticles.
Yang Wang and Hong Jin Fan
Small Early view (2012)
Logarithmic conductance as a function of T ^1/2 for the core–shell nanoparticles. Inset: sketch of the spin-polarized tunneling between two neighboring core–shell particles where the shells act as a tunneling barrier.

Biomedical Nanomagnetics: A Review

Excellent review article dedicated to biomedical applications of nanoparticles. Kannan Krishnnan has been awarded a IEEE prize for the article: congratulations!

Biomedical Nanomagnetics: A Spin Through Possibilities in Imaging, Diagnostics, and Therapy
Kannan M. Krishnan
IEEE Trans Magn. 46, 2523 (2010)

Size effect on manganite NP

Nanometer Size Effect on Magnetic Properties of Sm0.8Ca0.2MnO3 Nanoparticles.
Vladimir Markovich, Ivan Fita, Andrzej Wisniewski, Roman Puzniak, Dmitrii Mogilyansky, Przemyslaw Iwanowski, Piotr Dluzewski, and Gad Gorodetsky
J. Phys. Chem. 116, 435 (2012)
(a-d) Temperature dependence of real component of ac susceptibility (χ0) measured during heating at different frequencies and magnetic ac field of 10 Oe for SCMO samples. Insets show the imaginary part (χ00) of ac susceptibility measured at different frequencies and magnetic ac field of 10 Oe.

Wednesday 22 February 2012

Magnetic Hyperthermia of NP

 Some recent articles about modeling of hyperthermia in magnetic nanoparticle systems:

1) Role of dipole-dipole interactions for hyperthermia heating of magnetic nanoparticle ensembles.
C. Haase and U. Nowak
Phys. Rev. B 85, 045435 (2012)
Heating power per sample volume Ac vs
particle concentration c. Systems with different spatial distributions
(regular simple cubic and hexagonal structures as well as random
repellent and free particles) are compared. In all cases an optimal
density exists.


















Tuesday 21 February 2012

Laser induced demagnetization at high T

Theory of laser-induced demagnetization at high temperatures.
A. Manchon, Q. Li, L. Xu, and S. Zhang
Phys. Rev. B 85, 064408 (2012)
Time evolution of three-temperature model for a large laser-fluence case Te(0) = 1.6. The critical slowing down
of the spin system is identified as the plateau in the figure. The inset defines a slowdown time τd . The smaller inset shows the magnified region in the vicinity of the maximum temperature.

Friday 17 February 2012

Assymetric MR in EB bilayers

Asymmetric magnetoresistance in an exchange bias Co/CoO bilayer.
Sarbeswar Sahoo, Srinivas Polisetty, Yi Wang, Tathagata Mukherjee, Xi He, Sitaram S Jaswal and Christian Binek
J. Phys.CM 24, 096002 (2012)
Selected magnetoresistance curves with the external field H oriented parallel to the current I measured after cooling in a
field of 0H D 0:2 T from 320 K to the respective temperatures. The lines are the best fits according to equation (4).

Wednesday 15 February 2012

Size dependence of Exchange Bias

Size Dependence of Exchange Bias in Co/CoO Nanostructures
Sara Laureti, Sarah Y. Suck, Helge Haas, Eric Prestat, Olivier Bourgeois, and Dominique Givord

Phys. Rev. Lett. 108, 077205 (2012)
Temperature dependence of Heb in Co/CoO/Au samples measured for the three nanostructure sizes S (squares), M (dots), and L (triangles).

DW magnetoresistance contrinutions by multiscale simulations

Disentangling the Physical Contributions to the Electrical Resistance in Magnetic DomainWalls: A Multiscale Study.
K. M. Seemann, F. Garcia-Sanchez, F. Kronast, J. Miguel, A. Kákay, C. M. Schneider, and R. Hertel, F. Freimuth, Y. Mokrousov, and S. Blügel
Phys. Rev. Lett. 108, 077201 (2012)
XMCD photoelectron emission microscopy asymmetry images of L10-ordered FePd (a) and FePt (b) taken at the Fe
L3-absorption edge for the demagnetized domain state at room temperature and in zero magnetic field. The insets to the upper right corner show the result of micromagnetic simulations.

Thursday 9 February 2012

FM frustrated system in squared lattice

Ferromagnetic frustrated spin systems on the square lattice: Schwinger boson study.
H. Feldner, D. C. Cabra, and G. L. Rossini
Phys. Rev. B 84, 214406 (2011)
Classical phase diagram. F, ferromagnetic phase; CAF, collinear antiferromagnetic phase; CH, collinear helicoidal phase; H, helicoidal phase.

Quantum spin ice II

Quantum Ice: A Quantum Monte Carlo Study.
Nic Shannon, Olga Sikora, Frank Pollmann, Karlo Penc, and Peter Fulde
Phys. Rev. Lett. 108, 067204 (2012)
The ice configuration possessing the most flippable plaquettes is the squiggle state, shown here within a 40-site tetragonal cell. Arrows show the displacement of protons within Ic water ice or, equivalently, the orientation of spins in spin ice. The squiggle state possesses a net magnetic flux, orientated along a [100] axis.

Meron-like magnetic order in coupled discs

Direct Observation of Unconventional Topological Spin Structure in Coupled Magnetic Discs.
C. Phatak, A. K. Petford-Long, and O. Heinonen
Phys. Rev. Lett. 108, 067205 (2012)
(a) Schematic showing the spin structure of a meronlike state with opposite chirality; (b) schematic showing the trilayer discs and direction of the electron beam for imaging, and (c) LTEM under-focus image, and (d) reconstructed magnetic induction color map.

Monte Carlo simulation of Fe pnictides

Phase transitions in spin-orbital models with spin-space anisotropies for iron pnictides: Monte Carlo simulations.
Ryan Applegate and Rajiv R. P. Singh, Cheng-Chien Chen and Thomas P. Devereaux
Phys. Rev. B 85, 054411 (2012)
Phenomenological phase diagram for the spin-orbital model. The exchange energy scale in the problem sets the transition
temperature TO for orbital order, which in turn drives the structural transition. eps_0 is the energy scale below which long-wavelength fluctuations are suppressed. There are two separate continuous orbital
and magnetic transitions for eps<<eps_0 (shown as dotted and dashed lines, respectively) and one simultaneous first-order transition for eps>>eps_0 (shown as a solid line).

Ultrafast heating for magnetization reversal

Ultrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet.
T.A. Ostler, J. Barker, R.F.L. Evans, R.W. Chantrell, U. Atxitia, O. Chubykalo-Fesenko, S.El Moussaoui,L. Le Guyader, E. Mengotti, L.J. Heyderman, F. Nolting, A. Tsukamoto, A. Itoh, D. Afanasiev, B.A. Ivanov, A.M. Kalashnikova, K. Vahaplar, J. Mentink, A. Kirilyuk, Th. Rasing & A.V. Kimel
Nature Comms. 3, 666 (2012)

The magneto-optical images of a Gd24Fe66.5Co9.5 continuous film obtained after the action of a sequence of N 100 fs laser pulses.

Tuesday 7 February 2012

Triangular lattice AF realized experimentally

Experimental Realization of a Spin-1=2 Triangular-Lattice Heisenberg Antiferromagnet
Yutaka Shirata,1 Hidekazu Tanaka,1 Akira Matsuo,2 and Koichi Kindo
Phys. Rev. Lett. 108, 057205 (2012)
Crystal structure of Ba3CoSb2O9. The blue single octahedron is a CoO6 octahedron with a Co2+ ion at
the center, and the face-sharing Sb2O9 double octahedron is shaded ochre. Magnetic Co2þ ions form a regular triangular
lattice in the ab plane. Dotted lines denote the chemical unit cell.

Damping ans moment of inertia effects in 1st principles calculations

Atomistic Spin Dynamic Method with both Damping and Moment of Inertia Effects Included from First Principles.
Satadeep Bhattacharjee, Lars Nordström, and Jonas Fransson
Phys. Rev. Lett. 108, 057204 (2012)

The three contributions in the generalized LLG equation, the bare precession arising from the effective magnetic field, and the superimposed effects from the Gilbert damping and the moment of inertia.

Ultrafast reversal

Ultrafast Spin Dynamics in Multisublattice Magnets.
J. H. Mentink, J. Hellsvik, D.V. Afanasiev, B. A. Ivanov, A. Kirilyuk, A.V. Kimel, O. Eriksson, M. I. Katsnelson, and Th. Rasing
Phys. Rev. Lett. 108, 057202 (2012)

Atomistic spin dynamics simulation of laser-induced spin dynamics of a model GdFe system with either AFM or FM sublattice coupling. The spin dynamics of Gd is shown as function of the spin dynamics of Fe.

Spin and orbital moments in Fe clusters

Spin Coupling and Orbital Angular Momentum Quenching in Free Iron Clusters.
M. Niemeyer,1,2 K. Hirsch,1,2 V. Zamudio-Bayer,1,2 A. Langenberg,1,2 M. Vogel,1 M. Kossick,1,2 C. Ebrecht, K. Egashira,3 A. Terasaki,4,5 T. Mo¨ ller,2 B. v. Issendorff,6 and J. T. Lau

Phys. Rev. Lett. 108, 057201 (2012)
 Relative spin (filled circles) and orbital (open circles) magnetic moments of Fe+ n clusters normalized to the atomic values (muS= 4 muB and muL= 2 muB). While the spin moment remains at 60%–90%, the orbital value is strongly reduced already for Fe3+ .

Wednesday 1 February 2012

DW on ferroelectrics

Dynamics of charged domain walls in ferroelectrics.
M. Y. Gureev, P. Mokrý, A. K. Tagantsev, and N. Setter
ArXiv 1201.6331 (2012)

Zig-zag wall in a parallel plate capacitor. The pressure acting on each segment leads to non-zero force acting on the wall (a).

Nanooscillator characterized by MRFM

Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator.
A. Hamadeh, G. de Loubens, V.V. Naletov, J. Grollier, C. Ulysse, V. Cros, and O. Klein
ArXiv 1201.6344 (2012)

Phase diagram of the STNO autonomous dynamics measured by MRFM.