Chirally coupled nanomagnets

Science ◽  
2019 ◽  
Vol 363 (6434) ◽  
pp. 1435-1439 ◽  
Author(s):  
Zhaochu Luo ◽  
Trong Phuong Dao ◽  
Aleš Hrabec ◽  
Jaianth Vijayakumar ◽  
Armin Kleibert ◽  
...  
Keyword(s):  
Exchange Bias ◽  
Domain Walls ◽  
Logic Gates ◽  
Bias Field ◽  
Electric Control ◽  
Nonvolatile Memories ◽  
Magnetic Layers ◽  
Out Of Plane ◽  
Free Current ◽  
Moriya Interaction

Magnetically coupled nanomagnets have multiple applications in nonvolatile memories, logic gates, and sensors. The most effective couplings have been found to occur between the magnetic layers in a vertical stack. We achieved strong coupling of laterally adjacent nanomagnets using the interfacial Dzyaloshinskii-Moriya interaction. This coupling is mediated by chiral domain walls between out-of-plane and in-plane magnetic regions and dominates the behavior of nanomagnets below a critical size. We used this concept to realize lateral exchange bias, field-free current-induced switching between multistate magnetic configurations as well as synthetic antiferromagnets, skyrmions, and artificial spin ices covering a broad range of length scales and topologies. Our work provides a platform to design arrays of correlated nanomagnets and to achieve all-electric control of planar logic gates and memory devices.

scholarly journals Strong Interfacial Perpendicular Magnetic Anisotropy in Exchange-Biased NiO/Co/Au and NiO/Co/NiO Layered Systems

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1237
Author(s):  
Mateusz Kowacz ◽  
Błażej Anastaziak ◽  
Marek Schmidt ◽  
Feliks Stobiecki ◽  
Piotr Kuświk
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Bias ◽  
Direct Contact ◽  
Domain Walls ◽  
Perpendicular Magnetic Anisotropy ◽  
Bias Field ◽  
Layered Systems ◽  
Ferromagnetic Layers ◽  
Out Of Plane ◽  
And Control

The ability to induce and control the perpendicular magnetic anisotropy (PMA) of ferromagnetic layers has been widely investigated, especially those that offer additional functionalities (e.g., skyrmion stabilization, voltage-based magnetization switching, rapid propagation of domain walls). Out-of-plane magnetized ferromagnetic layers in direct contact with an oxide belong to this class. Nowadays, investigation of this type of system includes antiferromagnetic oxides (AFOs) because of their potential for new approaches to applied spintronics that exploit the exchange bias (EB) coupling between the ferromagnetic and the AFO layer. Here, we investigate PMA and EB effect in NiO/Co/Au and NiO/Co/NiO layered systems. We show that the coercive and EB fields increase significantly when the Co layer is coupled with two NiO layers, instead of one. Surrounding the Co layer only with NiO layers induces a strong PMA resulting in an out-of-plane magnetized system can be obtained without a heavy metal/ferromagnetic interface. The PMA arises from a significant surface contribution (0.74 mJ/m2) that can be enhanced up to 0.99 mJ/m2 by annealing at moderate temperatures (~450 K). Using field cooling processes for both systems, we demonstrate a wide-ranging control of the exchange bias field without perturbing other magnetic properties of importance.

scholarly journals Magnetic Configurations in Modulated Cylindrical Nanowires

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 600
Author(s):  
Cristina Bran ◽  
Jose Angel Fernandez-Roldan ◽  
Rafael P. del Real ◽  
Agustina Asenjo ◽  
Oksana Chubykalo-Fesenko ◽  
...  
Keyword(s):  
Domain Walls ◽  
Magnetocrystalline Anisotropy ◽  
Logic Gates ◽  
Local Domain ◽  
Magnetic Nanowires ◽  
Precise Control ◽  
Magnetic Layers ◽  
State Present ◽  
Circular Domains ◽  
3D Applications

Cylindrical magnetic nanowires show great potential for 3D applications such as magnetic recording, shift registers, and logic gates, as well as in sensing architectures or biomedicine. Their cylindrical geometry leads to interesting properties of the local domain structure, leading to multifunctional responses to magnetic fields and electric currents, mechanical stresses, or thermal gradients. This review article is summarizing the work carried out in our group on the fabrication and magnetic characterization of cylindrical magnetic nanowires with modulated geometry and anisotropy. The nanowires are prepared by electrochemical methods allowing the fabrication of magnetic nanowires with precise control over geometry, morphology, and composition. Different routes to control the magnetization configuration and its dynamics through the geometry and magnetocrystalline anisotropy are presented. The diameter modulations change the typical single domain state present in cubic nanowires, providing the possibility to confine or pin circular domains or domain walls in each segment. The control and stabilization of domains and domain walls in cylindrical wires have been achieved in multisegmented structures by alternating magnetic segments of different magnetic properties (producing alternative anisotropy) or with non-magnetic layers. The results point out the relevance of the geometry and magnetocrystalline anisotropy to promote the occurrence of stable magnetochiral structures and provide further information for the design of cylindrical nanowires for multiple applications.

scholarly journals Exchange bias in ferromagnetic bilayers with orthogonal anisotropies: the case of GaMnAsP/GaMnAs combination

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Suho Choi ◽  
Seul-Ki Bac ◽  
Xinyu Liu ◽  
Sanghoon Lee ◽  
Sining Dong ◽  
...  
Keyword(s):  
Exchange Bias ◽  
Easy Axis ◽  
Initial Conditions ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
The Other ◽  
Planar Hall Effect ◽  
Magnetic Layers ◽  
Out Of Plane ◽  
Magnetic Hysteresis Loops

Abstract We report the observation of exchange bias in a ferromagnetic Ga0.94Mn0.06As0.77P0.23/ Ga0.94Mn0.06As bilayer, in which the easy axis in one layer is oriented out-of-plane, and in the other in-plane. Magnetization reversal in this system is explored using planar Hall effect (PHE) measurements under various initial conditions and with various field-cooling orientations. Our results show that the two magnetic layers are ferromagnetically exchange-coupled, and that such coupling results in pronounced exchange-bias-like shifts of magnetic hysteresis loops during reversal of in-plane magnetization. The presence of exchange bias in this system can be understood on the basis of magnetic closure domains formed in the layer with the out-of-plane easy axis.

Magnetoresistance of Nanoscale Domain Walls Formed in Arrays of Parallel Nanowires

SPIN ◽  
2019 ◽  
Vol 09 (01) ◽  
pp. 1950004
Author(s):  
Jingchun Wang ◽  
Floriano Cuccureddu ◽  
Rafael Ramos ◽  
Cormac Ó. Coileáin ◽  
Igor V. Shvets ◽  
...  
Keyword(s):  
Thin Films ◽  
Domain Wall ◽  
Exchange Interaction ◽  
Exchange Bias ◽  
Room Temperature ◽  
Domain Walls ◽  
Nanowire Array ◽  
Bias Field ◽  
Nanowire Arrays ◽  
Exchange Bias Field

We present the possibility of enhancing magnetoresistance (MR) by controlling nanoscale domain wall (DW) width in a planar nanowire array. Results based on micromagnetic calculations show that DW width decreases with increasing exchange bias field and decreases with reducing exchange interaction between neighboring nanowires. Fe/Fe3O4 nanowire arrays were grown on [Formula: see text]-plane sapphire to demonstrate the feasibility of this concept, and an enhanced MR ratio of 3.7% was observed at room temperature. compared with flat and stepped Fe3O4 thin films.

The effect of Dzyaloshinskii–Moriya interaction on direct and backward transition between magnetic states of Pt/Co/Ir/Co/Pr synthetic ferrimagnet

2021 ◽  
Vol 6 (3) ◽  
pp. 167-178
Author(s):  
Artem D. Talantsev ◽  
Ekaterina I. Kunitsyna ◽  
Roman B. Morgunov
Keyword(s):  
Thin Layer ◽  
Domain Structure ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Ferromagnetic Layers ◽  
Magneto Optical Kerr Effect ◽  
Magnetic States ◽  
Fluctuation Fields ◽  
Moriya Interaction ◽  
Effect Technique

In this paper, we present the study of domain structure accompanying interstate transitions in Pt/Co/Ir/Co/Pr synthetic ferrimagnet (SF) of 1.1 nm thick and 0.6 – 1.0 nm thin ferromagnetic Co layers. Variation in the thickness of the thin layer causes noticeable changes in the domain structure and mechanism of magnetization reversal revealed by MOKE (Magneto-Optical Kerr Effect) technique. Magnetization reversal includes coherent rotation of magnetization of the ferromagnetic layers, generation of magnetic nuclei, spreading of domain walls (DW), and development of areas similar with strip domains, dependently on thickness of the thin layer. Inequivalence of the direct and backward transitions between magnetic states of SF with parallel and antiparallel magnetizations was observed in sample with thin layer thicknesses 0.8 nm and 1.0 nm. Asymmetry of the transition between these states is expressed in difference fluctuation fields and shapes of reversal magnetization nucleus contributing to the correspondent forward and backward transitions. We proposed simple model based on asymmetry of Dzyaloshinskii–Moriya interaction. This model explains competition between nucleation and domain wall propagation due to increase/decrease of the DW energy dependently on direction of the spin rotation into the DW in respect to external field.

scholarly journals Size dependence of the exchange bias field in NiO/Ni nanostructures

2000 ◽  
Vol 77 (23) ◽  
pp. 3815-3817 ◽  
Author(s):  
M. Fraune ◽  
U. Rüdiger ◽  
G. Güntherodt ◽  
S. Cardoso ◽  
P. Freitas
Keyword(s):  
Exchange Bias ◽  
Size Dependence ◽  
Bias Field ◽  
Exchange Bias Field

Exchange Bias Properties in Bulk Ni45Co5Mn38Sn12 Heusler Alloy

2014 ◽  
Vol 875-877 ◽  
pp. 272-276 ◽  
Author(s):  
Chao Jing ◽  
Ye Jun Yang ◽  
Dong Hua Yu ◽  
Zhe Li ◽  
Xiao Long Wang ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Exchange Bias ◽  
Heusler Alloy ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Bias Field ◽  
Magnetic Hysteresis Loop ◽  
Zero Field ◽  
Co Substitution ◽  
Exchange Bias Field

We report the exchange bias properties in the bulk Ni45Co5Mn38Sn12quaternary Heusler alloy. The ferromagnetic (FM) –antiferromagnetic (AFM) interactions get reinforced after the Co substitution for Ni in the Ni-Mn-Sn alloy, which increase the exchange bias field (HE). A maximum shift in hysteresis loops of 306 Oe was observed in the 10 kOe field cooled sample. The origin of this large exchange bias field has been discussed. Magnetic hysteresis loop obtained in the zero field cooled (ZFC) mode shows double-shifted loop, and the reason of this phenomenon has been explained in detail.

Sign in / Sign up

Export Citation Format

Share Document