Thermoelectric effects in spintronics

Magnon-drag thermopile.
Marius V. Costache, German Bridoux, Ingmar Neumann, and Sergio O. Valenzuela
Nature Mater. 11, 199 (2012)

Magnon-drag detection principle and geometry of the device.

Dynamics in frozen state of spin ice

Spin dynamics in the frozen state of the dipolar spin ice material Dy2Ti2O7.
L. R. Yaraskavitch, H. M. Revell, S. Meng, K. A. Ross, H. M. L. Noad, H. A. Dabkowska,
B. D. Gaulin, and J. B. Kycia
Phys. Rev. B 85, 020410(R) (2012)

Compilation of the ac susceptibility frequency scans of Dy2Ti2O7 and Ho2Ti2O7. An Arrhenius fit to the
low-temperature Dy2Ti2O7 relaxation is shown, along with a 6J_DTO_eff Arrhenius law with arbitrary frequency scaling.

Resistivity of individual DW

Tunable Resistivity of Individual Magnetic DomainWalls.
J. H. Franken, M. Hoeijmakers, H. J. M. Swagten, and B. Koopmans
PRL 108, 037205 (2012)

(a) Resistance change Delta R due to 20DWs in a Pt=Co=Pt strip as a function of Ga dose.
(b) Perpendicular anisotropy as a function of Ga dose. The red line is an exponential fit. (c) Normalized DW resistivity as a function of anisotropy. The red line is the theoretical result of the Levy-Zhang model . The same data are plotted in (d) as a function of DW width, showing the 1=Delta^2 dependence.

Magnetic relaxation of NP with dipolar interactions

Magnetic relaxation of a system of superparamagnetic particles weakly coupled by dipole-dipole interactions.
Pierre-Michel Déjardin
J. App. Phys. 110, 113921 (2011)

The relaxation time vs r as obtained from the diagonalization of the matrix A in Eq. (44) (solid line) and calculated with Eq.
(50) (dots) for k0 ¼ 0:05 and various values of h0 ¼ n=ð2rÞ. The dots on curve 1 are computed with Eq. (49).

Core/Shell NP structure from EELS

Distinguishing the core from the shell in MnOx/MnOy and FeOx/MnOx core/shell nanoparticles through quantitative electron energy loss spectroscopy (EELS) analysis.
S. Estradé, Ll. Yedra, A. López-Ortega, M. Estrader, G. Salazar-Alvarez, M.D. Baró, J. Nogués, F. Peiró
Micron 43, 30 (2012)

(a) HAADF images of several core–shell NPs. (b) L3 peak position and (c) Mn L3/L2 intensity ratio along the lines highlighted in the HAADF images, for the three considered nanoparticles. (d) Elemental quantification for the three considered NPs, and simulation considering a 2 nm thick an MnFe2O4 spinel around a Fe3O4 core. (e) Cartoon of the structure of the NPs.

Thermal switching of an anisotropic FM

Thermal switching rate of a ferromagnetic material with uniaxial anisotropy.
Tomohiro Taniguchi and Hiroshi Imamura
ArXiv 1201.5460 (2012)

The field h dependences of the normalized switchingrates, ˜r and rk. (a) ˜r (solid), r1 (dashed), and r2 (dotted,
inset) in the low field region. (b) ˜r, r1 (inset), and r2 in the high field region. (c), (d) ˜r, r1 (inset), and r3 in the low and
high field regions, respectively

Precession and relaxation of magnetic NP

Larmor precession and Debye relaxation of single-domain magnetic nanoparticles.
Zs. Jánosfalvi, J. Hakl and P.F. de Châtel
ArXiv 1201.5236 (2012)

Specific absorption rate as a function of frequency !, parameterized by field strength H0. Thick lines correspond to linear polarized cases, while dashed ones to circular polarized cases. Auxiliary thin line is drawn to explore behavior around resonance ! = 1. Maximum reached for each circular polarized case when condition ! > !L is fulfilled.

SW diffraction

SpinWave Diffraction and Perfect Imaging of a Grating.
S. Mansfeld, J. Topp, K. Martens, J. N. Toedt, W. Hansen, D. Heitmann, and S. Mendach
Phys. Rev. Lett. 108, 047204 (2012) 

Sketch of the experimental arrangement. S denotes the signal line, and G1 and G2 denote the ground lines of the coplanar wave guide. An exemplary TR-SKM phase image of the spin wave field taken at 10 mT and 4180 MHz is overlaid as a color density plot on a part of the Permalloy film.

Quantum spin ice III

Quantum strings in quantum spin ice.
Yuan Wan and Oleg Tchernyshyov
ArXiv 1201.5314 (2012)

Stochastic LLB equation

Stochastic form of the Landau-Lifshitz-Bloch equation.
R. F. L. Evans, D. Hinzke, U. Atxitia, U. Nowak, R. W. Chantrell, and O. Chubykalo-Fesenko
Phys. Rev. B 85, 014433 (2012)

LLB-I equation

LLB-II equation

Magnetization versus temperature (a) for the whole temperature range and (b) close to the Curie temperature Tc, for different system sizes. The results provided by the sLLB-II (lines) are always to the right with respect to those calculated within the sLLB-I (symbols). The black line represents an input me value.

Surface effects and dipolar interaction in NP

Surface effects on the magnetic behavior of nanoparticle assemblies.
G. Margaris, K. Trohidou, H. Kachkachi
Phys. Rev. B 85, 024419 (2012)

Magnetization as function of the applied field for a random anisotropy interacting assembly (g = 0.1) and for different
values of the surface anisotropy coefficients. (a) The value of the quadratic term (σ = 1) is smaller than the absolute value of the quartic term (w = ±2,±5,±8) together with the curve with only the core (quadratic) anisotropy term (w = 0). (b) The quadratic term (σ = 1) is equal or bigger than the absolute value of the quartic term (w = ±0.5,±1).

Exchange bias in La oxide lattices from as initio

Exchange bias in LaNiO3–LaMnO3 superlattices.
Marta Gibert, Pavlo Zubko, Raoul Scherwitzl, Jorge Íñiguez and Jean-Marc Triscone
Nature Mater. 11, 195 (2012)

Magnetic loops and temperature dependence of exchange bias field.

Results of the first-principles calculations.

Simulation of fcc Kagomé lattice

Monte Carlo simulations of magnetic ordering in the fcc Kagomé lattice
V. Hemmati, M. L. Plumer, and J. P. Whitehead
ArXiv 1201.4984 (2012)

Tuning exchange bias in core/shell NP

Tuning Exchange Bias in Core/Shell FeO/Fe3O4 Nanoparticles.
Xiaolian Sun, Natalie Frey Huls, Aruna Sigdel, and Shouheng Sun
Nano Lett. 12, 246 (2012)

Magnetic properties of Ni/NiO NPs

Several articles studying magnetic properties of Ni/NiO nanoparticles with different shapes and sizes:

Spin transfer in thick DW

Spin-transfer torque in a thick Néel domain wall
P. Balaz, V. K. Dugaev, and J. Barnás
Phys. Rev. B 85, 024416 (2012)

(a) The nonadiabaticity parameter β and (b) the nonadiabaticity parameter γ as a function of the exchange
parameter J , calculated for indicated values of η.

Collective SW excitations in coupled nanodots

Collective spin-wave excitations in a two-dimensional array of coupled magnetic nanodots.
Roman Verba and Gennadiy Melkov, Vasil Tiberkevich and Andrei Slavin

Spin-wave absorption spectra (a) and mode
structure [(b) and (c)] in a magnetic dot array in a FM ground
state having one defect per 11 × 11 dots.

Phys. Rev. B 85, 014427 (2012)

Regions of stability of different ground
states of a magnetic dot array in zero applied field: above the solid blue line both the FM and the CAFM ground states are stable; below the solid blue line, but above the dashed red line only the
CAFM ground state is stable; below the dashed red line both FM and CAFM states are unstable and array switches to a state with in-plane direction of the dot static magnetization.

 

e037206 (application/pdf Object)

Competing Ferri- and Antiferromagnetic Phases in Geometrically Frustrated LuFe2O4.
J. de Groot, K. Marty, M. D. Lumsden, A. D. Christianson, S. E. Nagler, S. Adiga, W. J. H. Borghols, K. Schmalzl, Z. Yamani, S. R. Bland, R. de Souza, U. Staub,8 W. Schweika, Y. Su, and M. Angst
Phys. Rev. Lett.108, 037206 (2012)

(a) H-T phase diagram, which exhibits a PM, an AFM, and a FM phase, extracted from various M(H) and M(T) curves. The hysteretic region where either FM or AFM can be stabilized is hatched. Arrows across phase lines indicate for which measurement direction it is observed given the hysteresis. Spin structure in C2/m cell of the AFM (b) and FM phase (c). Gray arrows indicate bilayer net magnetization

MQT in trigonal molecule magnets

Quantum tunneling of magnetization in trigonal single-molecule magnets.
Junjie Liu, Enrique del Barco, and Stephen Hill
Phys. Rev. B 85, 012406 (2012)

Zeeman diagram for a spin S =6 multiplet with easy-axis anisotropy [D<0 in Eq. (1)] and H//z. All possible nonzero tunneling gaps for C3 symmetry are labeled according to the scheme discussed in the main text. The inset shows the HT
dependence of the odd-n tunneling gaps.

Dynamics in rectangular elements

Magnetization dynamics and cone angle precession in permalloy rectangles.
Nils Kuhlmann, Andreas Vogel, and Guido Meier
Phys. Rev. B 85, 014410 (2012)

Exchange bias in Co/CoO trilayers

 Exchange bias in a Co/CoO/Co trilayer with two different ferromagnetic-antiferromagnetic interfaces.
A. N. Dobrynin, and D. Givord
Phys. Rev. B 85, 014413 (2012)

Temperature dependence of the coercive field (circles) and exchange-bias field (squares) for the first and trained loops for the bottom (a) and top (b) layers. The measurements at each temperature were performed after field cooling form 300 K under 1 T applied field

Neutron study of canted domains

Specular and off-specular polarized neutron reflectometry of canted magnetic domains in loose spin coupled CuMn/Co multilayers.
T. Saerbeck,, N. Loh, D. Lott, B. P. Toperverg, A. M. Mulders, M. Ali, B. J. Hickey,A. P. J. Stampfl, F. Klose, and R. L. Stamps
Phys. Rev. B 85, 014411 (2012)

See also the related entry: http://nanomagn.blogspot.com/2011/09/mapping-loose-spin-rkky-coupling.html

(a) Field dependence of the coupling angle 2 Dalta γ in the sample with 19 A° Cu0.94Mn0.06 (lines are a guide to the eye). (b) Temperature dependence of J1 and J2 reproduced from.8 the lines in (b) are fits obtained from the model reported by Saerbeck et al.

Biotemplated NP Arrays

Biotemplated Magnetic Nanoparticle Arrays.
Johanna M. Galloway, Jonathan P. Bramble, Andrea E. Rawlings, Gavin Burnell, Stephen D. Evans, and Sarah S. Staniland
Small 8, 204 (2012)

Magnetism in 1nm thick magnetite

Magnetism in nanometer-thick magnetite.
Matteo Monti, Benito Santos, Arantzazu Mascaraque, Oscar Rodríguez de la Fuente, Miguel Angel Niño,Tevfik Onur Mentes, Andrea Locatelli, Kevin F. McCarty, José F. Marco, and Juan de la Figuera
Phys. Rev. B 85, 020404(R) (2012)

(a) XAS and (b) XMCD image at705.8 eV. The field of view is 30 μm. (c) XMCD image recorded in remanence showing the magnetization pattern of the same crystal presented in Fig. 2(a). The field of view is 4 μm. The inset shows the experimental geometry. (d) (Top) XAS spectrum from the magnetite crystal. (Bottom) XMCD difference spectrum. The inset shows a typical XMCD spectra from stoichiometric magnetite.

Modeling of NP SANS by micromagnetics

Micromagnetic modeling and small-angle neutron scattering characterization of magnetic nanocomposites.
Sergey Erokhin, Dmitry Berkov, Nataliya Gorn, and Andreas Michels
Phys. Rev. B 85, 024410 (2012)

Comparison of the SANS intensities obtained experimentally (Exp., upper row) and simulated numerically
(Num. sim., lower row) for different external fields as indicated (a logarithmic scale for the intensities was used).