scholarly journals Graphene-mediated ferromagnetic coupling in the nickel nano-islands/graphene hybrid

2021 ◽  
Vol 7 (30) ◽  
pp. eabg7054
Author(s):  
Min Gao ◽  
Xiaowen Han ◽  
Wenjing Liu ◽  
Ziao Tian ◽  
Yongfeng Mei ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Density Functional ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Hysteresis Loops ◽  
Density Functional Theory Calculations ◽  
Electronic Systems ◽  
Coupling Mechanism ◽  
Magnetic Structures ◽  
Spintronic Devices

Nanoscale magnetic structures are fundamental to the design and fabrication of spintronic devices and have exhibited tremendous potential superior to the conventional semiconductor devices. However, most of the magnetic moments in nanostructures are unstable due to size effect, and the possible solution based on exchange coupling between nanomagnetism is still not clear. Here, graphene-mediated exchange coupling between nanomagnets is demonstrated by depositing discrete superparamagnetic Ni nano-islands on single-crystal graphene. The heterostructure exhibits ideal two-dimensional (2D) ferromagnetism with clear hysteresis loops and Curie temperature up to 80 K. The intrinsic ferromagnetism in graphene and antiferromagnetic exchange coupling between graphene and Ni nano-islands are revealed by x-ray magnetic circular dichroism and density functional theory calculations. The artificial 2D ferromagnets constitute a platform to study the coupling mechanism between complex correlated electronic systems and magnetism on the nanoscale, and the results and concept provide insights into the realization of spin manipulation in quantum computing.

scholarly journals Two-dimensional ferromagnetic superlattices

2019 ◽  
Vol 7 (4) ◽  
pp. 745-754 ◽  
Author(s):  
Shanshan Liu ◽  
Ke Yang ◽  
Wenqing Liu ◽  
Enze Zhang ◽  
Zihan Li ◽  
...  
Keyword(s):  
Density Functional ◽  
Magnetic Circular Dichroism ◽  
Hysteresis Loops ◽  
Density Functional Theory Calculations ◽  
Switching Behavior ◽  
Two Dimensional ◽  
Wafer Scale ◽  
Practical Applications ◽  
Spintronic Devices ◽  
Superlattice Structure

Abstract Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC 2D FM Fe3GeTe2 (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that TC of 4-layer Fe3GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, TC can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.

scholarly journals Control of the noncollinear interlayer exchange coupling

2020 ◽  
Vol 6 (48) ◽  
pp. eabd8861
Author(s):  
Zachary R. Nunn ◽  
Claas Abert ◽  
Dieter Suess ◽  
Erol Girt
Keyword(s):  
Exchange Coupling ◽  
Magnetic Moments ◽  
Interlayer Exchange Coupling ◽  
Magnetic Structures ◽  
Spintronic Devices ◽  
Spacer Layer ◽  
Ferromagnetic Layers ◽  
Almost All ◽  
Interlayer Exchange ◽  
Coupling Angle

Interlayer exchange coupling in transition metal multilayers has been intensively studied for more than three decades and is incorporated into almost all spintronic devices. With the current spacer layers, only collinear magnetic alignment can be reliably achieved; however, controlling the coupling angle has the potential to markedly expand the use of interlayer exchange coupling. Here, we show that the coupling angle between the magnetic moments of two ferromagnetic layers can be precisely controlled by inserting a specially designed magnetic metallic spacer layer between them. The coupling angle is controlled solely by the composition of the spacer layer. Moreover, the biquadratic coupling strength, responsible for noncollinear alignment, is larger than that of current materials. These properties allow for the fabrication and study of not yet realized magnetic structures that have the potential to improve existing spintronic devices.

Electronic Structure and Magnetic Properties of Ti-doped ZnO

2009 ◽  
Vol 1183 ◽  
Author(s):  
Soumia Lardjane ◽  
Ghouti Merad ◽  
Houda Imane Faraoun
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Magnetic Semiconductor ◽  
Magnetic Element ◽  
Functional Theory ◽  
Magnetic Structures ◽  
Spintronic Devices ◽  
The Density Functional Theory ◽  
Doped Zno ◽  
Ferromagnetic Ordering

AbstractRecent experiments suggest that Ti doped ZnO can be a promising room temperature dilute magnetic semiconductor (DMS) and a potentially useful material for spintronic devices. Furthermore, the fact that Ti doped ZnO shows ferromagnetic behaviour despite it contains no magnetic element makes this system good candidate for theoretical investigation regarding the controversies about the origin of ferromagnetic ordering in TM-doped ZnO. In this work, the density functional theory (DFT) is used to calculate the electronic and magnetic structures of Ti-doped ZnO. The obtained results are used to discuss the origin of the ferromagnetism, and the contribution of different atoms in the magnetic moment.

POSSIBLE Si-BASED HALF-METALLIC MATERIALS: MnSi46 CLATHRATES

2012 ◽  
Vol 26 (18) ◽  
pp. 1250114
Author(s):  
ZHI-WEI ZHAO ◽  
JING WANG ◽  
HUI-YAN ZHAO ◽  
YING LIU
Keyword(s):  
Density Functional ◽  
Magnetic Moments ◽  
Density Functional Theory Calculations ◽  
Metallic Materials ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Half Metallic ◽  
Silicon Clathrates ◽  
Ni Dopant ◽  
Center Site

The structural and magnetic properties of M Si 46 (M = Mn , Fe , Co and Ni ) clathrates have been studied using density functional theory calculations within the generalized gradient approximation. When the structures involve a dopant at the center of a Si 20 or Si 24 cage, the results show that the neighboring atoms around the dopant are drawn in toward the center. Some of the silicon clathrates with a Mn or Co dopant at the center site of a Si 20 cage, or a Mn , Fe or Ni dopant at the center site of a Si 24 cage are found to be half-metallic materials with large magnetic moments, and others with a Fe or Ni dopant at the center site of a Si 20 cage or a Co dopant at the center site of a Si 24 cage display semi-metallic characters. In particular, MnSi 46 with a half-metallic gap of 0.70 eV and a magnetic moment of 5.00 μ B shows promise for applications in the field of spintronics.

Magnetic Properties Study of the Nano-Alloy Fe1+xCo1−x by Monte-Carlo Simulations

SPIN ◽  
2019 ◽  
Vol 09 (01) ◽  
pp. 1950002 ◽  
Author(s):  
I. El Housni ◽  
H. Labrim ◽  
N. El Mekkaoui ◽  
S. Idrissi ◽  
R. Khalladi ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Magnetic Properties ◽  
Monte Carlo Simulations ◽  
Phase Diagrams ◽  
Ground State ◽  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Metropolis Algorithm ◽  
Spintronic Devices ◽  
Temperature Exchange

Motivated by spintronic devices and their applications, we engineer a model to investigate the magnetic properties of the magnetic nano-alloy Fe[Formula: see text]Co[Formula: see text]. Where [Formula: see text] is the fraction of iron atoms Fe substituted by the cobalt Co atoms, [Formula: see text] corresponds to 50% Fe atoms and 50% Co atoms, this compound is then called equiatomic FeCo. The purpose of this work is to apply the Monte-Carlo Simulations (MCS), under Metropolis algorithm to predict the magnetic properties of such system. In a first step, we propose a model describing this system including different exchange coupling interactions. Then, we establish and analyze the ground state phase diagrams, in different planes. For non-null temperature values, applied MCS under the Metropolis algorithm. The behavior of both the magnetizations and the susceptibilities are illustrated as a function of temperature. Also the effect of the different exchange coupling interactions is studied and discussed. The hysteresis loops are presented and analyzed for specific values of temperature, exchange coupling interactions and concentrations.

scholarly journals Atomic origin of spin-valve magnetoresistance at the SrRuO3 grain boundary

2020 ◽  
Vol 7 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Xujing Li ◽  
Li Yin ◽  
Zhengxun Lai ◽  
Mei Wu ◽  
Yu Sheng ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Density Functional ◽  
Magnetic Moments ◽  
Spin Valve ◽  
Density Functional Theory Calculations ◽  
Precise Knowledge ◽  
Transmission Electron ◽  
Defect Control ◽  
Scanning Transmission ◽  
Low Dimensional

Abstract Defects exist ubiquitously in crystal materials, and usually exhibit a very different nature from the bulk matrix. Hence, their presence can have significant impacts on the properties of devices. Although it is well accepted that the properties of defects are determined by their unique atomic environments, the precise knowledge of such relationships is far from clear for most oxides because of the complexity of defects and difficulties in characterization. Here, we fabricate a 36.8° SrRuO3 grain boundary of which the transport measurements show a spin-valve magnetoresistance. We identify its atomic arrangement, including oxygen, using scanning transmission electron microscopy and spectroscopy. Based on the as-obtained atomic structure, the density functional theory calculations suggest that the spin-valve magnetoresistance occurs because of dramatically reduced magnetic moments at the boundary. The ability to manipulate magnetic properties at the nanometer scale via defect control allows new strategies to design magnetic/electronic devices with low-dimensional magnetic order.

scholarly journals Influence of Ce, Nd, Eu and Tm Dopants on the Properties of InSe Monolayer: A First-Principles Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2707
Author(s):  
Zhi Xie ◽  
Limin Chen
Keyword(s):  
Density Functional ◽  
Diluted Magnetic Semiconductors ◽  
Magnetic Semiconductors ◽  
Magnetic Moments ◽  
Density Functional Theory Calculations ◽  
Infrared Range ◽  
Type Conductivity ◽  
Substitutional Doping ◽  
Low Dimension ◽  
Lanthanide Atoms

Doping of foreign atoms may substantially alter the properties of the host materials, in particular low-dimension materials, leading to many potential functional applications. Here, we perform density functional theory calculations of two-dimensional InSe materials with substitutional doping of lanthanide atoms (Ce, Nd, Eu, Tm) and investigate systematically their structural, magnetic, electronic and optical properties. The calculated formation energy shows that the substitutional doping of these lanthanide atoms is feasible in the InSe monolayer, and such doping is more favorable under Se-rich than In-rich conditions. As for the structure, doping of lanthanide atoms induces visible outward movement of the lanthanide atom and its surrounding Se atoms. The calculated total magnetic moments are 0.973, 2.948, 7.528 and 1.945 μB for the Ce-, Nd-, Eu-, and Tm-doped systems, respectively, which are mainly derived from lanthanide atoms. Further band structure calculations reveal that the Ce-doped InSe monolayer has n-type conductivity, while the Nd-doped InSe monolayer has p-type conductivity. The Eu- and Tm-doped systems are found to be diluted magnetic semiconductors. The calculated optical response of absorption in the four doping cases shows redshift to lower energy within the infrared range compared with the host InSe monolayer. These findings suggest that doping of lanthanide atoms may open up a new way of manipulating functionalities of InSe materials for low-dimension optoelectronics and spintronics applications.

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