Skyrmions in PdFe bilayers

Formation of magnetic skyrmions with tunable properties in PdFe bilayer deposited on Ir(111)
E. Simon, K. Palotas, L. Rozsa, L. Udvardi, and L. Szunyogh

Phys. Rev. B 90, 094410 (2014)

Magnitudes of the Fe-Fe DM vectors for PdFe/Ir(111) as a function of the interatomic distance measured in units of the in-plane lattice constant (a2D) for different Fe layer relaxations. The inset shows a sketch of the in-plane components of the calculated DM vectors between a central Fe atom (C) and its nearest and next nearest Fe neighbors at −5% relaxation

Spin flop in AF

Successive spin-flop transitions of a Neel-type antiferromagnet Li2MnO3 single crystal with a honeycomb lattice.
K. Balamurugan,1,2 Sang-Hyun Lee,1,3 Jun-Sung Kim,4 Jong-Mok Ok,4 Youn-Jung Jo,5 Young-Mi Song,6 Shin-Ae Kim, E. S. Choi,8 Manh Duc Le,1,2 and Je-Geun Park

Phys. Rev. B 90, 104412 (2014)

Imaging spin waves

Close-up on spin dynamics.

Stanislas Rohart and Guillemin Rodary

Nature Materials 13, 770 (2014) 

Imaging of spin waves in atomically designed nanomagnets.

A. Spinelli, B. Bryant, F. Delgado, J. Fernández-Rossier and A. F. Otte

Nature Materials 13, 782 (2014)

a, Schematic view of spin-wave excitation on a six-atom chain using scanning tunnelling microscopy. The highest efficiency is obtained when the tip is placed at an edge atom. b, Principle of spin-wave-assisted magnetization reversal in the chain. The switching, due to thermal and/or quantum fluctuations, is much faster when the scanning tunnelling microscope (STM) excites the chain in a spin-wave (SW) state.

Frustration in artificial spin ice

The unhappy wanderer.
R. L. Stamps
Nature Physics 10, 623 (2014)

Emergent ice rule and magnetic charge screening from vertex frustration in artificial spin ice.

Ian Gilbert, Gia-Wei Chern, Sheng Zhang, Liam O’Brien, Bryce Fore,, Cristiano Nisoli and Peter Schi effer

Nature Physics 10, 670 (2014)

An initial spin (green) is placed arbitrarily on an empty lattice. A second spin is placed on a neighbouring lattice segment in a direction parallel to the first, unless the spins share a vertex, in which case the direction of the spin reverses (if the vertex is traversed in a straight line) or rotates (if a turn is taken). Subsequent spins placed in the same way eventually reach the starting position and close the loop (red). A lattice is considered 'happy' (a) when these rules can be obeyed at every segment along the loop, and 'unhappy' or vertex-frustrated (b) when they fail.

Spin Hall Effect is electric

SHE’s electric.
Kyoung-Whan Kim and Hyun-Woo Lee
Nature Physics 10, 549 (2014)

Spin Hall effect tunnelling spectroscopy.
Luqiao Liu, Ching-Tzu Chen , J. Z. Sun
Nature Physics 10, 561 (2014)

a, The spin–orbit interaction gives rise to an illusory magnetic field aligned parallel to the spin direction of flowing electrons (thick grey arrow). The red (blue) arrow outside the material denotes the magnetic field for spin-up (spi…

Goethite NPs

Magnetic properties of ultra-small goethite nanoparticles.

E Brok, C Frandsen, D E Madsen, H Jacobsen, J O Birk, K Lefmann, J Bendix, K S Pedersen, C B Boothroyd, A A Berhe,G G Simeoni and S Mørup
J. Phys. D 47, 365003 (2014)

ZFC/FC magnetization curves for the sample GBM obtained in an applied field of (top) 4.8 T and (bottom) 2.0 mT. The magnetization is given per kg of goethite in the sample.

Spin transfer torques in AF

Spin Pumping and Spin-Transfer Torques in Antiferromagnets.
Ran Cheng, Jiang Xiao, Qian Niu, and Arne Brataas
Phys. Rev. Lett. 113, 057601 (2014)

The two eigenmodes of Eq. (2) have opposite chiralities and opposite ratios between the cone angles of m1 and m2. A magnetic field along the easy axis breaks the degeneracy of the two modes.

Thermal stability of skyrmion lattice

Thermal Stability of an Interface-Stabilized Skyrmion Lattice.

A. Sonntag, J. Hermenau, S. Krause, and R. Wiesendanger

Phys. Rev. Lett. 113, 077202 (2014)

(a)–(c) SP-STM data of Fe/Ir(111) at different temperatures. For all images the same color scale and tunneling parameters were used (25×25  nm2, U=10  mV I=4  nA). The insets show the corresponding Fourier transforms. Black circles mark the contribution from the magnetic unit cell and gray circles the spots caused by the TAMR effect. (d) Line profiles along the direction indicated in (a)–(c).

Coupled Skyrmions

Flower-like dynamics of coupled Skyrmions with dual resonant modes by a single-frequency microwave magnetic field.
Yingying Dai, Han Wang, Teng Yang, Weijun Ren & Zhidong Zhang
Scientific Reports 4, 6153 (2014)

Sketch of the topological density distribution and two excitation modes of skyrmion dynamics.

Three dimensional magnetic abacus memory

Three dimensional magnetic abacus memory.

ShiLei Zhang, JingYan Zhang, Alexander A. Baker, ShouGuo Wang, GuangHua Yu, Thorsten Hesjedal

Scientific Reports 4, 6109 (2014)

(a) Generic concept for magnetic 3D memory. Typically several magnetic units are stacked on top of each other, where each unit stores one bit of information. In a conventional scheme, the magnetisation state of a unit depends on the sequence of bits in the stack, i.e., |1000〉, …, |0001〉 going from left to right in the example shown. However, if the layers are treated as indistinguishable, the state of the stack is adequately described by only counting the number of spin-up layers. In this way, all four states shown in (a) have the same logic value of ‘1’. (b–f) illustrate the five logic states a four-layer stack can store: |0〉, |1〉, |2〉, |3〉, and |4〉, respectively. This counting scheme is analogous to the beads in an abacus, as shown for comparison.

Artificial Frustrated Systems

Focus on artificial frustrated systems.
J Cumings, L J Heyderman, C H Marrows and R L Stamps
New J. Phys. 16, 075016 (2014)

Artificial spin ices. (a) XMCD-PEEM image of artificial spin ice, captured in the so-called 'string regime' [7], while undergoing thermal relaxation from an energetically excited, saturated moment, configuration down to one of the two degenerate ground states. Nanomagnets with moments pointing towards the bottom/left appear in blue contrast, while nanomagnets with moments pointing up/right appear in red contrast. Scale bar 2 μm. (b) X-ray transmission micrograph of a CoFeB artificial square ice with the overlaid red gridlines showing the square lattice. Magnetic contrast is shown in the inset, where islands that have reversed under thermal excitation at 100 °C appear with bright contrast. Scale bar 1 μm. (c) Lorentz transmission electron micrograph of artificial kagome ice after thermal excitation. The magnetization direction within the arms of the array can be determined from the detailed intensity profile across the arm [8], allowing the magnetic charge at each vertex to be inferred. Positive and negative magnetic charges are indicated by the overlaid red and blue dots, showing that the sample is in the charge-ordered, kagome ice-II state. Scale bar 500 nm. (d) The number of configurations that can be created in an artificial square ice by an applied field is very sensitive to disorder. The diagram represents all possible configurations that can be realized by application of the field (with magnitude slightly larger than the mean coercive field) to sixteen elements starting from a saturated type II state with a distribution of switching fields. Each unique configuration is indicated by a circular dot

Magnetic Nanoparticles: a Review

Magnetic Nanoparticles: A Subject for Both Fundamental Research and Applications.
S. Bedanta, A. Barman, W. Kleemann, O. Petracic, and T. Seki
Journal of Nanomaterials 952540 (2013)

The 2014 Magnetism Roadmap

The 2014 Magnetism Roadmap.

Robert L Stamps, Stephan Breitkreutz, Johan Åkerman, Andrii V Chumak, YoshiChika Otani, Gerrit E W Bauer, Jan-Ulrich Thiele, Martin Bowen, Sara A Majetich, Mathias Kläui, Ioan Lucian Prejbeanu, Bernard Dieny, Nora M Dempsey and Burkard Hillebrands

Journal of Physics D 47, 333001 (2014)

Imaging Spin waves

Close-up on spin dynamics.
Stanislas Rohart and Guillemin Rodary
Nature Materials 13, 770 (2014)

Imaging of spin waves in atomically designed nanomagnets.
A. Spinelli, B. Bryant, F. Delgado, J. Fernández-Rossier and A. F. Otte
Nature Materials 13, 782 (2014)

Multiferroics and spin: A Review

Multiferroics of spin origin.
Yoshinori Tokura, Shinichiro Seki, and Naoto Nagaosa

Rep. Prog. Phys. 77, 076501 (2014)

The 2014 Magnetism Roadmap.

The 2014 Magnetism Roadmap.
Robert L Stamps, Stephan Breitkreutz, Johan Åkerman, Andrii V Chumak, YoshiChika Otani, Gerrit E W Bauer, Jan-Ulrich Thiele, Martin Bowen, Sara A Majetich, Mathias Kläui, Ioan Lucian Prejbeanu, Bernard Dieny, Nora M Dempsey and Burkard Hillebrands
J. Phys. D 47, 333001 (2014)

Fast time evolution of noneq spins states

Theory of fast time evolution of nonequilibrium spin states in magnetic heterostructures.
I. A. Yastremsky, Peter M. Oppeneer, and B. A. Ivanov
Phys. Rev. B.90, 024409 (2014)

Time evolutions of the total magnetization in the Ni layer from its initial value, both for parallel and antiparallel configurations (ɛ=0.1) The dashed line presents the approximate result from Eq. (10). Note that here and henceforth in corresponding figures the value of the function MNi(t) at t=0 is chosen as zero, i.e., only the essential remagnetization dynamics is shown.

Thermal gradient DW motion

Thermodynamic theory for thermal-gradient-driven domain-wall motion.
X. S. Wang and X. R. Wang

http://doi.dx.org/10.1103/PhysRevB.90.014414

Au@Co3O4 NP for catalysis

Synthesis of Monodispere Au@Co3O4 Core-Shell Nanocrystals and Their Enhanced Catalytic Activity for Oxygen Evolution Reaction.

Zhongbin Zhuang, Wenchao Sheng and Yushan Yan

Advanced Materials 26, 3950 (2014)

Novel OER catalysts – monodisperse Au@Co₃O₄ core-shell nanocrystals – have been prepared by synthesizing Au nanocrystals, followed by deposition of Co shells and their conversion to Co₃O₄ shells. Owing to the synergistic effect, Au@Co₃O₄ nanocrystals have an OER activity 7 times as high as a Au and Co₃O₄ nanocrystals mixture or Co₃O₄ nanocrystals alone, and 55 times as high as Au nanocrystals alone

Thermally assisted skyrmion motion

Thermally assisted current-driven skyrmion motion.
Roberto E. Troncoso, and Alvaro S. Núñez

Phys. Rev. B 89, 224403 (2014)

Ultrafast demagnetization

Imaging Ultrafast Demagnetization Dynamics after a Spatially Localized Optical Excitation.
C. von Korff Schmising, B. Pfau, M. Schneider, C. M. Günther, M. Giovannella, J. Perron, B. Vodungbo, L. Müller, F. Capotondi, E. Pedersoli, N. Mahne, J. Lüning, and S. Eisebitt
Phys. Rev.Lett.11, 217203 (2014)

Zero modes in magnetic systems

Zero modes in magnetic systems: General theory and an efficient computational scheme.

F. J. Buijnsters, A. Fasolino, and M. I. Katsnelson

Phys. Rev. B 89, 174433 (2014)

Quantum spin ice. Reviews

Quantum spin ice: a search for gapless quantum spin liquids in pyrochlore magnets.

M J P Gingras and P A McClarty
Rep. Prog. Phys. 77, 056501 (2014)


Monte Carlo studies of the dipolar spin ice model
Roger G Melko and Michel J P Gingras J. Phys.: Condens. Matter 16, R1277 (2014)

Skyrmions in FePt layers

Skyrmion magnetic structure of an ordered FePt monolayer deposited on Pt(111).
S. Polesya, S. Mankovsky, S. Bornemann, D. Ködderitzsch,1 J. Minár, and H. Ebert

Phys. Rev. B 89, 184414 (2014)

Magnetic moment distribution within the Skyrmion. Yellow and blue colors in (a) represent schematically the region giving gain and loss of Zeeman energy in the presence of a magnetic field; blue color in (b) shows the region giving loss of the exchange energy contributed by in-plane components of magnetic moments. (c) and (d): Structure of single Sk obtained with the contributions of the Fe-Pt exchange interactions taken into account [the same color code as in (a) and (b)].

Effects of dimensionality and spatial distribution on the magnetic relaxation of interacting ferromagnetic nanoclusters: A Monte Carlo study

Effects of dimensionality and spatial distribution on the magnetic relaxation of interacting ferromagnetic nanoclusters: A Monte Carlo study.
D. Brinis, A. Laggoun, D. Ledue and  R. Patte

J. Appl. Phys. 115, 173906 (2014)

χ ac /χ0 vs T for the xy-square lattice with various strengths of the DI (f = 10⁴ Hz). (a) χ′ and (b) χ″.

Amazing physics of magnetized chains of beads

Magnetic ghosts and monopoles. N Vandewalle and S Dorbolo 2014

New J. Phys. 16, 013050 (2014)

The magneto-elastica: from self-buckling to self-assembly.
Dominic Vella, Emmanuel du Pontavice,  Cameron L. Hall and Alain Goriely

Proc. Royal Soc. A 470 20130609 (2013)

Three simple experiments that illustrate the resistance to deformation of assemblies of ferromagnetic spheres. (a) The self-buckling of a vertical chain of magnetic spheres as further spheres are added. (b) The prolate–oblate oscillation of a ring of magnetic spheres. Snap-shots of the motion are shown at intervals of 0.021 s. (c) A self-assembled chiral ‘nano-tube’. In each case, the diameter of the spheres is 2a=5 mm and the magnetic field strength is B= 1.195 T.