Helicity control in magnetic nanotubes

Tailoring dual reversal modes by helicity control in ferromagnetic nanotubes.
H. D. Salinas, J. Restrepo, and Òscar Iglesias

Phys. Rev. B 101, 054419 (2020)

Magnetic configurations along the hysteresis loops for the different reversal modes displayed in Fig. 4 (left and right columns correspond to panels (a) and (c) of that figure). Upper panels represent the height profiles of the quantities ⟨θ⟩, ⟨mz⟩, and <mϕ⟩  averaged per layer for the tube (8,15) and γ= 0.035, whereas lower ones present snapshots of the spin configurations taken at points labeled in Fig. 4.

Thernal Stability of Circular Nanomagnets

Thermal Stability of Magnetic States in Circular Thin-Film Nanomagnets with Large Perpendicular Magnetic Anisotropy.

Gabriel D. Chaves-O’Flynn, Georg Wolf, Jonathan Z. Sun, and Andrew D. Kent

Phys. Rev. Applied 4, 024010 (2015)

Energy barriers normalized to U0 calculated by the domain-wall model Eq. (14) (dashed lines) and obtained with the string method (solid points) for different applied fields and disk diameters. The black solid line corresponds to the macrospin model without applied field.

Ultrafast dynamics in FePt

Modeling of Ultrafast Heat- and Field-Assisted Magnetization Dynamics in FePt

P. Nieves and O. Chubykalo-Fesenko

Phys. Rev. Applied 5, 014006 (2016)

Snapshots of the system magnetization state in the continuous film with F=40  mJ/cm3 and μ0Hz=−3  T at time moments (a) t=0.25  ns, (b) t=0.5  ns, (c) t=3.2  ns, and (d) t=3.6  ns. The figures show an area of 150×150  nm.

High-frequency magnetization dynamics of individual atomic-scale magnets

High-frequency magnetization dynamics of individual atomic-scale magnets.

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

Phys. Rev. B 93, 064407 (2016)

(a) Telegraphic noise z(t) on a nanomagnet at low and high I at closed feedback loop, and respective data histograms. (U=100 mV, T=45 K) (b) Top: Periodic sequence of high and low tunnel bias. Bottom: Resulting noise I on a thermally switching nanomagnet at constant tip-sample distance. (c) Averaged noise signal during one cycle, calculated from I(t) in (b).

Magnetization reversal of an individual exchange-biased permalloy nanotube

Magnetization reversal of an individual exchange-biased permalloy nanotube.

A. Buchter, R. Wölbing, M. Wyss, O. F. Kieler, T. Weimann, J. Kohlmann, A. B. Zorin, D. Rüffer, F. Matteini, G. Tütüncüoglu, F. Heimbach, A. Kleibert, A. Fontcuberta i Morral, D. Grundler, R. Kleiner, D. Koelle, and M. Poggio

Phys. Rev. B 92, 214432 (2015)

Training effect: (a) SQUID and (b) DCM hysteresis loops for different loop number n at T=3.4 K. Red and blue curves indicate up- and down-sweep, respectively. Evolution of (c) exchange field and (d) coercivity with increasing loop number n extracted from SQUID data set. Dashed line fits the data according to Eq. (2). Point size corresponds to the measurement error in field

Criteria for saturated magnetization loop

Criteria for saturated magnetization loop.

A. Harres, M. Mikhov, V. Skumryev, A.M.H. de Andrade, J.E. Schmidt, J. Geshev

J. Magn. Magn. Mater.402, 76 (2015)

M(H  ) loops calculated for a disordered system of non-interacting single-domain uniaxial-anisotropy particles using $H_{\max }^{+}/H_{\mathrm{A}}=1.2$, where $H_{\max }^{-}/H_{\mathrm{A}}=-1.2$ (panel (a)) and $H_{\max }^{-}/H_{\mathrm{A}}=-0.8$ (panel (b)). The first (panels (c) and (d)) and the second (panels (e) and (f)) derivatives of the respective descending and ascending branches for negative fields are also given. Although $H_{\max }^{+}/H_{\mathrm{A}}=1.2$ for both loops and their derivatives, only the regions of interest are plotted. The bottom panels show the −m_d(H)$-m_{\mathrm{d}}\left(H\right)$ and m_r(H)$m_{\mathrm{r}}\left(H\right)$ (the latter obtained starting from a random magnetization state) remanence curves; the first derivatives of −m_d(H)$-m_{\mathrm{d}}\left(H\right)$ are plotted in the insets.

Autoresonant switching of NPs

Autoresonant switching of the magnetization in single-domain nanoparticles: Two-level theory.
Guillaume Klughertz, Lazar Friedland, Paul-Antoine Hervieux and Giovanni Manfredi

Phys. Rev. B 91, 104433 (2015)

Amplitude of the |A2|2 level in the two-parameter space (ε,a1−0.5), obtained from numerical solutions of Eqs. (14) and (15). Regions where |A2|2 is larger are those of efficient population transfer (i.e., efficient magnetization switching).

Target skyrmion switching by current

Switching of a target skyrmion by a spin-polarized current. 
Yan Liu, Haifeng Du, Min Jia, and An Du 

Phys. Rev. B 91, 094425 (2015)

Topography of mz during the skyrmion polarity switching process. The insets on the lower right show mz in the disk plane. The insets on the upper right display the cutlines along the diameter through the disk center. (i) Variation of the Rs with simulation time.

 

Magnetization reversal in nanodisks

Magnetization reversal by confined droplet growth in soft/hard hybrid nanodisks with perpendicular anisotropy.
J.-P. Adam, S. Rohart, J.-P. Jamet, J. Ferré, A. Mougin, R. Weil, H. Bernas, and G. Faini
Phys. Rev. B 85, 214417 (2012)

(a) Expected spontaneous magnetization M_s variation along the nanodisk radius. (b) PMOKE image difference between the remnant state after a magnetic field pulse (27 mT, 200 ns) and the remnant state after saturation under 500 mT during 5 s.

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).

Control of magnetism atom by atom

Atom-by-atom engineering and magnetometry of tailored nanomagnets.
Alexander Ako Khajetoorians, JensWiebe, Bruno Chilian, Samir Lounis, Stefan Blügel and RolandWiesendanger
Nature Physics AOL (2012)

Antiferromagnetic chains of even and odd numbers of Fe atoms. Top panels: magnetization states from pair-KKR Ising model (left, partly degenerate) and magnetic images (right) of chains of antiferromagnetically coupled Fe atoms on Cu(111) with a lengths of three (a) to seven (e) atom

Control of ferroelectics magnetization by E field

Electric Field Control of Nonvolatile Four-State Magnetization at Room Temperature.
Sae Hwan Chun, Yi Sheng Chai, Byung-Gu Jeon, Hyung Joon Kim, Yoon Seok Oh, Ingyu Kim, Hanbit Kim, Byeong Jo Jeon, So Young Haam, Ju-Young Park, Suk Ho Lee, Jae-Ho Chung, Jae-Hoon Park, and Kee Hoon Kim
Phys. Rev. Lett. 108, 177201 (2012)

The MðEÞ curves at zero H bias obtained after applying four different ME poling (states 0, 1, 2, and 3) as
indicated in the inset.

Information transfer by spin chirality

Information transfer by vector spin chirality in finite magnetic chains.
Matthias Menzel, Yuriy Mokrousov, Robert Wieser, Jessica E. Bickel, Elena Vedmedenko, Stefan Blügel, Stefan Heinze, Kirsten von Bergmann, André Kubetzka, and Roland Wiesendanger
ArXiv 1204.2650 (2012)

SP-STM measurements of Fe chains on Ir(001). (a) and (b) Typical sample area of 30 x 30 nm2 measured with an Fe-coated
W tip without and with an applied external magnetic field of B = +2 T perpendicular to the sample surface, respectively (constant current images colorized with simultaneously acquired dI/dU maps, measurement parameters: U = +500mV, I = 5 nA, T = 8 K).(c) Topographic line profiles of the same Fe chain at B = 0 T and B = 2 T measured with a Cr-coated tip. The insets show schematically the tip magnetization and how a 120 deg spin-spiral, which is inverting in opposite fields, could explain the experimental results.

Bistability in atomic AF chains

Bistability in Atomic-Scale Antiferromagnets.
Sebastian Loth, Susanne Baumann, Christopher P. Lutz, D. M. Eigler, Andreas J. Heinrich
Science 335, 196 (2012)

Magnetization distribution in an FeO NP by SANS

Quantitative spatial magnetization distribution in iron oxide nanocubes and nanospheres by polarized small-angle neutron scattering.
S Disch1, E Wetterskog, R P Hermann, A Wiedenmann,U Vainio, G Salazar-Alvarez, L Bergström and Th Brücke
New Journal of Physics 14, 013025 (2012)

Purely nuclear SANS of spherical and cubic nanoparticles (scaled by 0.5 for display). Lines indicate fits to the model depicted in the right inset. Left inset: 10 deg sectors used for integrating the two-dimensional (2D) scattering.

Reversal of individual Co islands

Magnetization Reversal of Individual Co Nanoislands.
S. Ouazi, S. Wedekind, G. Rodary, H. Oka, D. Sander, and J. Kirschner
Phys. Rev. Lett. 108, 107206 (2012)

Island size dependence of the energy barrier Delta E. (a) The blue curve is a linear fit Delta E_lin=K(N-N0)The red curve shows the calculated energy barrier for domain wall formation Delta E_dw= 4 sigma sqrt(AK).
.

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.

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 Gd₂₄Fe_66.5Co_9.5 continuous film obtained after the action of a sequence of N 100 fs laser pulses.

Calculating coercivity at finite T

Calculation of coercivity of magnetic nanostructures at finite temperatures.
D. Suess, L. Breth, J. Lee, M. Fuger, C. Vogler, F. Bruckner, B. Bergmair, T. Huber, and J. Fidler
Phys. Rev. B 84, 224421 (2011)

(a) Geometry and finite element mesh of the model of a granular grain. The initial magnetization and the saddle point configuration at the coercive field for a field applied 75◦ off the long axis of the particle is shown. These states are used for the calculation of the attempt frequency. (b) Angular dependence of the coercive field (μ0Hc) of a CoCrPtO granular medium. Black solid line, downward-pointing triangles: Experimental obtained values extracted from Ref. 32.

Electric switching of magnets

Electric toggling of magnets.
Evgeny Y. Tsymbal
Nature Mater. 11, 3205 (2012)

Electric-field-induced toggle switching of magnetization. a, Schematic of the experiment performed by Wang and colleagues.