Thermally assisted STT reversal

Thermally assisted spin-transfer torque magnetization reversal in uniaxial nanomagnets.
D. Pinna, Aditi Mitra, D. L. Stein and A. D. Kent
Appl. Phys. Lett. 101, 262401 (2012)

Mean switching time versus current in the sub-critical low current regime (I<1).

Magnetic NP for Cancer Diagnosis: Review

Special issue on Magnetic Nanoparticles for Biomedical Applications.

Magnetic Nanoparticles for Cancer Diagnosis and Therapy.
Mehmet V. Yigit & Anna Moore & Zdravka Medarova
Pharm Res (2012) 29:1180–1188

MQT in a free NP

Quantum tunneling of the magnetic moment in a free nanoparticle.
M.F. O'Keeffe, E.M. Chudnovsky, D.A. GaraninJMMM 324, 2871 (2012)

Dependence of energy on J at K=J   and _Iz/_Ix=2$I_z/I_x=2$ for different values of α$\alpha$. The plot shows first-order quantum phase transition on α$\alpha$.

Hyperthermia and dipolar interactions in Fe-MgO NPs

Adjustable Hyperthermia Response of Self-Assembled Ferromagnetic Fe-MgO Core–Shell Nanoparticles by Tuning Dipole–Dipole Interactions.
Carlos Martinez-Boubeta, Konstantinos Simeonidis, David Serantes, Iván Conde-Leborán, Ioannis Kazakis, George Stefanou, Luis Peña, Regina Galceran, Lluis Balcells, Claude Monty, Daniel Baldomir, Manassis Mitrakas and Makis Angelakeris
Advanced Funtional Materials 22, 3737 (2012)

The correlations arising from dipole–dipole interactions and their influence on the hyperthermia efficacy are studied both theoretically and experimentally and found to be in quantitative agreement. The calculation represents an analytical model of hyperthermia in magnetic interacting particle systems to explain in a simple way the ubiquitous behavior observed in this class of materials.

Hybrid NP for cancer: Review

Hybrid Nanoparticles for Detection and Treatment of Cancer.
Michael J. Sailor and Ji-Ho ParkAdvanced Materials 28, 3779 (2012)

EB of magnetoelectronic materials

Exchange biasing of magnetoelectric composites.
Enno Lage, Christine Kirchhof, Viktor Hrkac, Lorenz Kienle, Robert Jahns, Reinhard Knöchel,  Eckhard Quandt & Dirk Meyners Nature Materials 11, 523 (2012)

Z-contrast image of the Fe₅₀Co₅₀ multilayer system on a AlN substrate (right-hand side of the image, columnar grown) and a magnified view (inset) with a line indicating the selected area for chemical analysis

SW excitation by STT

Spin-Wave Excitation in Magnetic Insulators by Spin-Transfer TorqueJiang Xiao and Gerrit E. W. Bauer
Phys. Rev. Lett. 108, 217204 (2012)

An electrically insulating magnetic film of thickness d with magnetization m (∥ẑ at equilibrium) in contact with a normal metal. A spin current J_s∥ẑ is generated in the normal metal and absorbed by the ferromagnet.

Magnetometer in pigeons

An Avian Magnetometer
Michael Winklhofer
Science 336, 991 (2012)

Glas transition in dipolar magnets?

Unreachable glass transition in dilute dipolar magnet.
A. Biltmo & P. Henelius ncomms1857.pdf (application/pdf Object)

The experimental data (black dots) are from Quilliam et al.¹³, whereas red lines are best fits to equation (3) at temperatures 0.10, 0.11, 0.12, 0.14, 0.15, 0.17 and 0.20 K from left to right.

Magnetic DW Injector

Highly Efficient In-Line Magnetic Domain Wall Injector.
Timothy Phung, Aakash Pushp, Luc Thomas, Charles Rettner, See-Hun Yang, Kwang-Su Ryu, John Baglin, Brian Hughes, and Stuart Parkin

Nano Letters 15, 835 (2015)

We demonstrate a highly efficient and simple scheme for injecting domain walls into magnetic nanowires. The spin transfer torque from nanosecond long, unipolar, current pulses that cross a 90° magnetization boundary together with the fringing magnetic fields inherently prevalent at the boundary, allow for the injection of single or a continual stream of domain walls. Remarkably, the currents needed for this “in-line” domain wall injection scheme are at least one hundred times smaller than conventional methods.

Trapping skyrmions in a hole

Capturing of a magnetic skyrmion with a hole.
Jan Müller and Achim Rosch

Phys. Rev. B 91, 054410 (2015)

Snapshot of a micromagnetic simulation of skyrmion driven by a current (D=0.3J/a, μB=0.09J/a2, vs=0.001aJex, and α=β=0.4) in the presence of a single vacancy: a missing spin (gray sphere). The trajectory of the skyrmion center is indicated by a red line.

Spin waves in Heisenberg AF

Spin-wave multiple excitations in nanoscale classical Heisenberg antiferromagnets.
Zhuofei Hou and D. P. Landau, G. M. Stocks, G. Brown

Phys. Rev. B 91, 064417 (2015)

The spectra for ST(r0,q,ω) obtained from isotropic, antiferromagnetic nanofilms with the same Lxy=20 and three different thicknesses, i.e., Lz=10, 20, and 30. The results were obtained in the PBCXY [100] directions, i.e., the directions parallel to the free surfaces, with r0⇒bulkcenter at T=0.4TN with SD parameters of nt=5000,ncutoff=4000, and dt=0.2/|J|. We give the spectra for nq=0,1,2,...,5. N is the total number of initial configurations.

Nonmonotonic residual entropy in diluted spin ice: A comparison between Monte Carlosimulations of diluted dipolar spin ice models and experimental results.
T. Lin, X. Ke, M. Thesberg, P. Schiffer, R. G. Melko, and M. J. P. Gingras

Phys. Rev. B 90, 214433 (2014)

Spin Spirals in Mn

Thermal properties of a spin spiral: Manganese on tungsten (110)
G. Hasselberg, R. Yanes, D. Hinzke, P. Sessi, M. Bode, L. Szunyogh, and U. Nowak

Phys. Rev. B 91, 064402 (2015)

Sketch of the calculated DM vectors Dij up to the fifth NN shell of the 2D lattice formed by the Mn atoms. The DM vectors (grey arrows) are placed at the center of the line connecting the center atom (red sphere) and its corresponding neighbor (green sphere). The length of the DM vector is proportional to its magnitude and also reflects the orientation in space. Note the rapid decay in the magnitude of DM vectors with distance; see also Fig. 1. Green arrows represent the magnetic moment.

Dynamics and inertia of skyrmions

Dynamics and inertia of skyrmionic spin structures.

Felix Büttner, C. Moutafis, M. Schneider3, B. Krüger1, C. M. Günther3, J. Geilhufe5, C. v. Kor Schmising3, J. Mohanty3‡, B. Pfau3, S. Scha ert3, A. Bisig1, M. Foerster1, T. Schulz1, C. A. F. Vaz1,6, J. H. Franken7, H. J. M. Swagten7, M. Kläui and S. Eisebitt

Nature Physics 11, 225 (2015)

Illustration of the topology of skyrmionic spin structures with a disk-shaped domain space.b, A magnetic bubble, which covers the sphere exactly once (N = 1). The poles are mapped to extended areas (the inner and outer domains). Hence, all spins at the boundary of the domain space point in the same direction, which confines the inner domain and the domain wall. This is the structure investigated in the present work. c, A chiral skyrmion, which has a different radial distribution from that of the bubble⁵. Topologically, however, both are the same, as the bubble can be obtained from the chiral skyrmion by expanding its inner domain. d, A hedgehog skyrmion, which is again topologically equivalent to the other figures. The hedgehog skyrmion can be continuously deformed to the chiral skyrmion by rotating all spins by 90° around an axis normal to the plane.

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.