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Experimental evidence of coupling interaction between charge ordering and spin ordering

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Science China(Physics,Mechanics & Astronomy) 2010年第7期53卷 1255-1260页

作者： HONG Bo CAO GuangHan XU ZhuAn College of Materials Science and Engineering China Jiliang UniversityHangzhou 310018China Department of Physics Zhejiang UniversityHangzhou 310027China

In order to experimentally probe into the complicated interaction between charge ordering and spin ordering in manganites,two sets of samples Nd0.5Sr0.5Mn1-xGaxO3(NSMGO) and Nd 0.5Sr0.5Mn1-y CryO3(NSMCO)(0.0 x,y 0.075),have been studied by means of electrical transport,magnetization,electron spin resonance and transmission electron microscopy *** comparing the influence of Cr-doping and Ga-doping in the Nd0.5Sr0.5MnO3(NSMO) system,large difference between the evolution of charge ordering temperature T co in the Cr-doping and the Ga-doping cases is *** the NSMCO system,the CE-type antiferromagnetic(AFM)/charge ordering(CO) phase disappears with only 2.5 percent Cr doping;but in the NSMGO system,the CE-type AFM/CO phase always *** phenomenon indicates that the charge ordering formation is dominated by the spin *** a result,it is experimentally proved that there is strong coupling interaction between charge ordering and spin ordering in NSMO system.

关键词： perovskite manganites phase transitions order-disorder effects

Electrical Transport and Magnetic Properties of La_(0.67)Ca_(0.33)Mn_(1-x)Cr_xO_3 and La_(0.67+x)Ca_(0.33-x)Mn_(1-x)Cr_xO_3(0.04≤x≤0.08)

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Journal of Wuhan University of Technology(Materials Science) 2008年第4期23卷 463-466页

作者： XIAO Xun YUAN Songliu YIN Shiyan CHEN Ling REN Guangming MIAO Juhong YU Gongqi School of Physics Science and Technology Yangtze University Jingzhou 434023 China Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

A comparative study for two different series, La0.67Ca0.33Mn1-xCrxO3 and La0.67＋xCa0.33-x Mn1-xCrxO3 is performed with x changing from 0.04 to 0.08 through measurements of zero-field resistivity （p）, magnetoresistance （MR） and ac susceptibility （Z） as functions of temperature （T）. For the second group, a single insulator-metal transition was characterized by the resistivity maximum appears in p vs. T curve. For the first group, besides the resistivity peak appearing at higher temperatures, the sample shows evidence for the existence of another peak appearing at lower temperatures. Compared to the first group, the second group shows a significant enhancement in MR effect, while the measurement ofΧ-T dependence does not display obvious differences for the two series. Different behaviors observed in the two series are discussed by considering possible exchange interaction between Mn^3- ion and Cr^3- ion.

关键词： perovskite manganites double exchange metal-insulator transition colossal magnetoresistance

Focused-Ion-Beam Induced Paramagnetic Defects in FAMn:PbI3 perovskite Films

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Advances in Chemical Engineering and Science 2022年第2期12卷 87-95页

作者： Nam Joong Jeon Jangwon Seo Yanghee Kim Ji Yeong Lee Sugyeong Hong Sun Hee Kim Jung-Keun Lee Division of Advanced Materials Korea Research Institute of Chemical Technology Daejeon Korea Advanced Analysis Center Korea Institute of Science and Technology Seoul Korea Western Seoul Center Korea Basic Science Institute Seoul Korea Physics Department Division of Liberal Arts & Sciences Hanil University & PTS Wanju Korea

FAMn:PbI3 perovskite films were synthesized and probed mainly through electron spin resonance (ESR) spectroscopy. FAMn:PbI3 with low (~1%) Mn concentration showed a hyperfine sextet line originated from Mn++ ions. FAMn:PbI3 with high (10%) Mn concentration showed broad resonance (~500 G peak-to-peak linewidth). However, after bombardment of FAMn:PbI3 with high Mn concentration by focused ion beams (FIB), a sharp ESR peak appeared. The peak-to-peak linewidth (ΔHpp) was ~8 G regardless of the temperature. The FIB-induced defect showed Curie behavior at low temperatures (5 K - 50 K), which indicates the presence of localized electrons at the defect sites at low temperatures. The g-value increased from g = 2.0002 to 2.0016 as the temperature increased from 5 K to 50 K. Together with the ongoing search for electron spin echo (ESE), this could potentially provide a platform for realizing magnetic bits, information storage, and increased manipulation speed.

关键词： perovskite manganites FIB Paramagnetic Spins

Electric and magnetic behaviour in double doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3

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Chinese Physics B 2007年第1期16卷 258-265页

作者：屈哲皮雳樊济宇谭舜张贝张锰张裕恒 Structure Research Laboratory University of Science and Technology of China Hefei 230026 China

The double-doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3＋/Mn^4＋ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the ＂double-doping＂.

关键词： perovskite manganites double doping phase separation variable-range hopping mechanism

Enhancement of “intrinsic” magnetoresistance ratio and activation energy of La0.67Ca0.33MnO3 single crystals by Fe doping

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Chinese Physics B 2005年第8期14卷 1653-1656页

作者：寇志起邸乃力马骁李庆安成昭华 StateKeyLaboratoryofMagnetism InstituteofPhysicsChineseAcademyofSciencesBeijing100080China

In order to avoid the complicated influence of grain boundaries on the resistivity in the investigation of the 'intrinsic' magnetoresistance (MR) effect, the magnetic and magnetotransport properties of La0.67Ca0.33MnO3 and La0.67Ca0.33Mn0.96Fe0.04O3 single crystals were investigated. Owing to the absence of grain boundaries in the single crystals, MR ratio under 40× 105A/m is about two orders of magnitude larger than that in polycrystalline counterparts.A further enhancement of MR ratio from 3400% to 17600% was achieved by a few percent of Fe doping. On the basis of the small polaron model, the activation energy derived from fitting the resistivity above Tc was found to increase upon introducing Fe. A connection between the strong localization of electrons arising from magnetic polarons and the enhancement of MR was observed in the single crystals.

关键词： perovskite manganites colossal magnetoresistance (CMR) magnetic polarons

Influence of Photon Pump Fluence on Charge Carriers in FAPbI3 and Manganite perovskites

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Advances in Chemical Engineering and Science 2022年第1期12卷 54-64页

作者： Nam Joong Jeon Jangwon Seo Sanghee Nah Jung-Keun Lee Division of Advanced Materials Korea Research Institute of Chemical Technology Daejeon Korea Seoul Center Korea Basic Science Institute Seoul Korea Physics Department Division of Liberal Arts and Sciences Hanil University & PTS Wanju Korea

FAPbI3 and FA(Mn:Pb)I3 perovskite films were prepared and evaluated through steady and transient absorption spectroscopy. According to the analysis using Elliot’s model, there were no considerable differences except for the absorption intensity between FAPbI3 and FA(Mn:Pb)I3 perovskite films: the value of the optical gap (Eg) and the position of exciton resonance (E0) were the same. The femtosecond transient absorption showed biexponential relaxation properties of the charge carriers, suggesting that biexcitons are more easily generated in FA(Mn:Pb)I3 than FAPbI3 perovskite. The generation of biexcitons in FA(Mn:Pb)I3 was also confirmed by the photon pump fluence dependence. Moreover, we were able to estimate the average number of absorbed photons directly from the photon pump pow

关键词： FAPbI3 perovskite manganites Transient Absorption