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Tunable exchange bias in La1.5Sr0.5CoMnO6 double perovskite doped with nonmagnetic Ga ions
Zhang Hongguang,Chen Wei,Xie Liang,Zhao HuiHui,Li Qi 한국물리학회 2022 Current Applied Physics Vol.35 No.-
The crystal structure, electronic structure, and magnetic behaviors of nonmagnetic Ga ions doped double perovskite La1.5Sr0.5CoMnO6 single phase crystals have been investigated. Different from the traditional magnetic dilution effect of nonmagnetic doping, Ga doping in La1.5Sr0.5CoMnO6 enhances the ferromagnetic (FM) exchange interaction of Co3+-O-Mn3+. Moreover, both conventional and spontaneous exchange bias (EB) effects can be tuned by modulating the Ga doping content, which is accompanied by the variation of the Co3+/4+ and Mn3+/4+ and the effective magnetic moment. The EB field and magnetization can be improved by nonmagnetic Ga3+ doping with content lower than 0.2. The evolution of conventional and spontaneous EB effects in La1.5Sr0.5Co1-xGaxMnO6 can be understood in terms of the unidirectional interface anisotropic coupling between FM/anti-FM, and/or FM/spin glass, which is affected by antisite disorder, spin glass, and the uncompensated coupling between Co and Mn.
The exchange bias effect and Griffiths phase in La1.5Sr0.5Co1-Ni MnO6: The impact of the divalent Ni
Zhang Hongguang,Wang Sen,Chen Wei,Wang Mingjun,Li Yongtao,Xie Liang 한국물리학회 2023 Current Applied Physics Vol.53 No.-
The effects of Co-site doping of Ni2+ ions on the crystal structure, electronic structure, and magnetic properties of La1.5Sr0.5CoMnO6 are investigated. The doping causes an increase in the anti-site disorder and a change in the content of Co2+/3+ and Mn3+/4+, as well as a change in the spin state of Co ions. Ni doping introduces Ni2+-O2-- Mn4+ ferromagnetic interactions to increase the ferromagnetic transition temperature. Samples display different dominant clusters, and field cooling promotes the presence of ferromagnetic clusters, allowing an increase in the Griffiths phase. Interestingly, Ni doping enables tuning the conventional and spontaneous exchange bias (EB) effects, increasing the EB field for intermediate concentrations. Moreover, the maxima of both EB fields do not occur in the same sample, which leads to a new understanding of the relationship between these two effects. The possible mechanisms related to the uncompensated spin and competition between ferromagnetic and antiferromagnetic clusters are discussed, respectively.
Zhang Xiaobing,Li Hongguang,Cao Wei 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.6
It is discussed that a new method for active power measurement under the conditions of distortion signals. Accurate measurement of the power consumed by the distorted signals has been focused on in recent years due to its practical utilities. In this work, a mathematical description of powers is deducted in the conditions of distorted signals according to a simplified model of the electrical network. Then, a rational measuring method of the electric energy for distorted signals is proposed on the basis of the analysis of the power flow. Also, a measuring method based on multiple wavelets was employed for measuring the active power in the conditions of unsteady distorted signals. Experimental results demonstrate that, by using the simulated typical distorted signals, the proposed measurement method can produce extremely accurate results compared to theoretical results.
Xiaomin Jin,Yuanan Liu,Wenhao Fan,Fan Wu,Hongguang Zhang 보안공학연구지원센터 2015 International Journal of Future Generation Communi Vol.8 No.2
Nowadays, many network devices have more than one network interface. Meanwhile, many protocols have been proposed to utilize multiple paths simultaneously. MPTCP (Multipath TCP) is a transport layer protocol that transfers data by multiple paths simultaneously, which is designed to improve the throughput and increase robustness of end to end transmission. However, when we use MPTCP, we find that MPTCP can not improve the throughput but even reduce the throughput in some cases. In this paper, we study this issue. Firstly, we study the effects of path characteristics for throughput of MPTCP, and find that path characteristics especially those bad paths have a great impact on the performance of MPTCP. Secondly, we analyze the reasons why the bad path characteristics have a serious impact on throughput of MPTCP, and propose a path selection method based on throughput prediction model and available bandwidth to improve the throughput. Finally, we validate our path selection method by simulations, and the results show that our method can improve the throughput of MPTCP.