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Thickness effect on magnetocrystalline anisotropy of MnPt(0 0 1) film
Qurat-ul-ain,Cuong, Do Duc,Odkhuu, Dorj,Rhim, S.H.,Hong, S.C. Elsevier 2018 Journal of magnetism and magnetic materials Vol.467 No.-
<P><B>Abstract</B></P> <P>We investigated the magnetocrystalline anisotropy (MCA) of MnPt(0 0 1) film and MnPt/MgO(0 0 1) using <I>ab initio</I> electronic structure calculations. We found that the magnetic ground state of the MnPt film strongly depends on thickness (n). In bulk and in film with n ≥ 7 monolayers; AFM-II is the magnetic ground state. However, as the film thickness reduces, the magnetic ground state shifts from AFM-II to AFM-III. We employ layer-by-layer Heisenberg model to explain thickness dependent ground state transition. AFM-III state in the Mn-terminated film shows large perpendicular MCA(PMCA), which further enhances on a MgO(0 0 1) substrate. We conclude that the interface plays a key role for the enhancement of PMCA on the substrate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thickness- and surface-termination- dependent MCA of MnPt(0 0 1) film is investigated. </LI> <LI> The Mn-terminated MnPt(0 0 1) film has different magnetic ground state from in bulk when thickness is <7 ML. </LI> <LI> The magnetic structures of the film are studied phenomenologically using rather simplified Heisenberg model. </LI> <LI> The Mn-terminated MnPt(0 0 1) film in AFM-III state shows PMCA when thickness is <9 ML. </LI> <LI> From calculations on MnPt/MgO(0 0 1) it is found that the Mn-O interface enhance PMCA significantly. </LI> </UL> </P>
Qurat-ul-ain Sahi,김용수 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6
In this article, we conducted molecular dynamics simulations to investigate the effect of applied strainand temperature on irradiation-induced damage in alpha-zirconium. Cascade simulations were performedwith primary knock-on atom energies ranging between 1 and 20 KeV, hydrostatic and uniaxialstrain values ranging from 2% (compression) to 2% (tensile), and temperatures ranging from 100 to1000 K. Results demonstrated that the number of defects increased when the displacement cascadeproceeded under tensile uniaxial hydrostatic strain. In contrast, compressive strain states tended todecrease the defect production rate as compared with the reference no-strain condition. The proportionsof vacancy and interstitial clustering increased by approximately 45% and 55% and 25% and 32% for 2%hydrostatic and uniaxial strain systems, respectively, as compared with the unstrained system, whereasboth strain fields resulted in a 15e30% decrease in vacancy and interstitial clustering under compressiveconditions. Tensile strains, specifically hydrostatic strain, tended to produce larger sized vacancy andinterstitial clusters, whereas compressive strain systems did not significantly affect the size of defectclusters as compared with the reference no-strain condition. The influence of the strain system on radiationdamage became more significant at lower temperatures because of less annealing than in highertemperature systems.
A Comprehensive Review on High-efficiency RF-DC Converter for Energy Harvesting Applications
Muhammad Basim,Qurat ul Ain,Khuram Shehzad,Syed Adil Ali Shah,Azam Ali,ByeongGi Jang,YoungGun Pu,Joon-Mo Yoo,Kang-Yoon Lee 대한전자공학회 2022 Journal of semiconductor technology and science Vol.22 No.5
The design of radiofrequency energy harvesting (RFRH) circuit for wearable devices, wireless sensor networks, and IoT applications can be classified mainly into radio frequency to direct current (RF-DC) converter, a transmitter and receiver antenna, an impedance matching network, and a storage device or a load. By scavenging RF energy from the ambient environment, this developing technology allows low-power wireless devices to be self-sustaining and environment friendly. To eliminate the need for batteries, RFEH technology has become a dependable and promising alternative for extending the lifetime of power-constrained wireless networks. This paper mainly focused on the input and output power, Power conversion efficiency (PCE), and sensitivity. Due to the weak and limited signal strength of received RF power, high-efficiency state-of-the-art RF energy harvesters must be designed to provide sufficient DC supply voltage to wireless networks. We provide in-depth information on the system's parameters. Optimum efficiency and maximum output power are the main concerns of an RFEH system. Therefore, RF Energy harvesting system review, antenna design, impedance matching, and RF-DC converter are presented in this paper to provide a deep insight into the design of the RFEH system. This article may help in identifying new research in the field of RF Energy Harvesting.