Rev. Mod. Phys. 89, 025006 (2017) - Interface-induced phenomena in magnetism

Interface-induced phenomena in magnetism.
Frances Hellman et al.Rev. Mod. Phys. 89, 025006 (2017)

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.

Non-Boolean computing with nanomagnets for computer vision applications : Nature Nanotechnology : Nature Publishing Group

Non-Boolean computing with nanomagnets for computer vision applications.
Sanjukta Bhanja, D. K. Karunaratne, Ravi Panchumarthy, Srinath Rajaram, Sudeep Sarkar

Nature Nanotechnology 11, 177 (2016)

Stages in object recognition:a, Grey-scale satellite image of an urban area. b, Edge image with extracted edge segments from a. c, Traditional approach to solving a quadratic optimization process using a CMOS-based arithmetic and logic unit (ALU). d, Proposed method to solve the quadratic optimization process using a magnetic coprocessor. e, Salient edge segments identified from b using the method in c. f, Objects identified using salient edges obtained from e.

DM anisotropy in nanomagnets with in-plane magnetization

Dzyaloshinskii-Moriya anisotropy in nanomagnets with in-plane magnetization.
M. Cubukcu, J. Sampaio, K. Bouzehouane, D. Apalkov, A. V. Khvalkovskiy, V. Cros, and N. Reyren
Phys. Rev. B 93, 020401(R) (2016)

DMI-induced anisotropy orthogonal to the shape anisotropy as observed by MFM and simulations. All scale bars are 200 nm long. The arrows indicate the mean magnetization. (a) Experimental MFM phase images are displayed. The actual topographical shape is indicated by a dotted line. The MFM phase is coded in the same way as in Fig. 1. The approximate sizes are 730×260,250×100, and 160×50 nm2. (b) Corresponding simulations for different D values (all the other micromagnetic parameters fixed), using an ideal dipolar MFM tip 30 nm above the magnetic layer. The observations of the magnetization direction in ellipses of different shapes (but same materials) allow constraining the Dzyaloshinskii-Moriya interaction strength D: The shadings indicate the D values compatible with observations. In the intermediate case, the magnetization does not align along one of the axes, reflecting the minute energy difference between the states with different magnetization directions. (c) Map of the DMI and exchange energy densities (darker means lower energy density) for the case D=2.1 mJ/m2. The energy gain concentrates close to the edges.

 

Scaling approach to MC simulations of magnetic models

Bridging the gap between discrete and continuous magnetic models in the scaling approach. E. A. Velásquez, J. Mazo-Zuluaga, P. Vargas, and J. Mejía-López
Phys. Rev. B 91, 134418 (2015)

Collapsed phase diagram for different scaling λ values. The inset shows the phase diagram for some selected scaling values, i.e., before the scaling up process.

Time resolved relaxation of nanomagnet

Time-resolved magnetic relaxation of a nanomagnet on subnanosecond time scales.
H. Liu, D. Bedau, J. Z. Sun, S. Mangin, E. E. Fullerton, J. A. Katine, and A. D. Kent
Phys. Rev. B 85, 220405 (2012)

(a) The total switching probability P_AP→P^double as a function of the second-pulse duration t₂ for a current I₁ of 8.5 mA and different delays. The dashed line is the switching probability P_AP→P⁽²⁾ for a single 8.5 mA pulse of duration t₂. (b) The same data are plotted with shifted time axis, with the shift dependent on the delay δt(t_delay). The data closely overlap, showing that the switching probability of a double pulse (t₁+t_delay+t₂) is the same as that of a single pulse with a longer duration, i.e., t₂+δt(t_delay), as illustrated schematically by the pulses drawn within the figure.

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

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)

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

Review on topological effects on nanomagnetism

Topological effects in nanomagnetism: from superparamagnetism to chiral quantum solitons.
Hans-Benjamin Braun
Advances in Physics 61, 1 (2012)

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 a_c. In the figure we plot the blocking temperature T_b(h) and the critical temperatures T_c(h) for arrays of three different values of the lattice constant (a > a_c, a < a_c, a = a_c (this last one in red)) as a function of the height of the nano-islands h. h* is the stopping height, after which T_b >  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.

SC vortex dynamics induced by micromagnets

Imaging the Statics and Dynamics of Superconducting Vortices and Antivortices Induced by Magnetic Microdisks.
R. B. G. Kramer, A.V. Silhanek, W. Gillijns, and V.V. Moshchalkov
Phys. Rev. X 1, 021004 (2011)

Probing the mobility of vortex-antivortex pairs. (a), (d) Scanning Hall Microscopy images at H=0 and T=6.9 K for two different magnetic moments of the disks. (b),(e) Scanning ac-susceptibility images taken with h=0.2 Oe and h=0.6 Oe, and a frequency of excitation 77 Hz. Panels (c) and (f ) show a superposition of panels (a) and (b), and (d) and (e).

Image recovery using nanomagnets

An ultrafast image recovery and recognition system implemented with nanomagnets possessing biaxial magnetocrystalline anisotropy.
Noel D'Souza, Jayasimha Atulasimha, and Supriyo Bandyopadhyay
ArXiv 1109.6932 (2011)

Recovering an image corrupted by noise by encoding in different magnetic states.

Phase locking in nanooscillator

Phase locking of dynamical modes in a nanomagnetic oscillator with a circularly spin-polarized current.
Jui-Hang Chang, Hao-Hsuan Chen, and Ching-Ray Chang, Yaowen Liu
Phys. Rev. B 84, 054457 (2011)

(a) The coordinate system of the device. The direction of the effective field heff is along the ez axis. (b) A schematic configuration of a spin valve with circularly spin-polarized current.

Diamond-domain structures

Magnetization splitting in Landau and diamond-domain structures: Dependence on exchange interaction, anisotropy, and size.
Kaixuan Xie,1 Xiaopu Zhang,1 Weiwei Lin,2,* Peng Zhang,1 and Hai Sang
Phys. Rev. B 84, 054460 (2011)

(a) and (b) Two initial magnetization states for relaxing into the Landau domain structure (c) and
diamond-domain structure (d), respectively. (e) Dependence of total energy on the anisotropy constantK. (f) Dependence of total energy on the exchange coefficient A.

Spintronics with molecular nanomagnets

Graphene Spintronic Devices with Molecular Nanomagnets.
Andrea Candini, Svetlana Klyatskaya, Mario Ruben, Wolfgang Wernsdorfer, and Marco Affronte
nl2006142 (application/pdf Object)