To insight into the B-site ordering in RFe_(0.5)Cr_(0.5)O_(3)ceramics,a series of RFe_(0.5)Cr_(0.5)O_(3)ceramics(R=La,Y,Lu)were synthesized by the sol-gel method,and the structural and magnetic properties were systemi...To insight into the B-site ordering in RFe_(0.5)Cr_(0.5)O_(3)ceramics,a series of RFe_(0.5)Cr_(0.5)O_(3)ceramics(R=La,Y,Lu)were synthesized by the sol-gel method,and the structural and magnetic properties were systemically investigated.By using the Rietveld refinement of all samples,it is found that the structural distortion is increased as the R ionic radius decreases,leading to the weakened interactions between Fe/Cr ions.Moreover,the Fe and Cr are arranged in disorder in LaFe_(0.5)Cr_(0.5)O_(3),but partially ordered in YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3),showing an increasing trend of the proportion of ordered domains with the decrease of R ionic radius.Through fitting the temperature-dependent magnetizations,it is identified that the magnetization reversal(MR)in disorder LaFe_(0.5)Cr_(0.5)O_(3)is resulted from the competition between the moments of Cr and Fe sublattices.In the partially ordered YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3)ceramics,because of the presence of Fe-O-Cr networks in the ordered domains whose moment is antiparallel to that of Fe-O-Fe and Cr-O-Cr in the disordered domains,the compensation temperature T_(comp)of MR is increased by nearly 50 K.These results suggest that the changing of R-site ions could be used very effectively to modify the Fe-O-Cr ordering,apart from the structural distortion,which has a direct effect on the magnetic exchange interactions in RFe_(0.5)Cr_(0.5)O_(3)ceramics.Then at values of composition where ordered domains are expected to be larger in number as compared to disordered domains and with a weaker structural distortion,one can expect a higher transition temperature Tcomp,providing a different view for adjustment of the magnetic properties of RFe_(0.5)Cr_(0.5)O_(3)ceramics for practical applications.展开更多
Lanthanum manganite with cation vacancies from nominal La（0.75）Sr（0.25）Mn（0.92）△（0.08）O（3-δ） nanocrystalline powder was successfully prepared at different calcination temperatures using the sol-gel method....Lanthanum manganite with cation vacancies from nominal La（0.75）Sr（0.25）Mn（0.92）△（0.08）O（3-δ） nanocrystalline powder was successfully prepared at different calcination temperatures using the sol-gel method. X-ray diffraction shows that as the calcination temperature（T（Cal）） increases, the crystal particle diameter increases, but the B-site vacancy content decreases. According to a powder diffraction profile fitting technique and transmission electron microscopy results, the vacancy content can be estimated as 0.08,0.01, and 0.005 for T（Cal） = 1073,1273, and 1473 K, respectively. Magnetization versus temperature curves show that the magnetic transition temperatures, including the Curie temperature, are influenced by both B-site vacancies and double-exchange interaction between Mn^（3＋） and Mn^（4＋） cations. A core-shell model is proposed for vacancies located on the surfaces of the crystal particles. As an application, the magnetic moment angle θ（ij） between Mn^（3＋） and Mn^（4＋） cations on the surface, which decreases with decreasing vacancy content, can be obtained.展开更多
基金supported by the Natural Science Foundation of Henan Province,China(Grant Nos.232300420353 and 232300420392)the Key Scientific Research Project of Higher Education of Henan Province(Grant No.24B140001)+2 种基金the Doctor Scientific Research Initiate Fund of Anyang Institute of Technology(Grant No.BSJ2022010)the National Basic Research Program of China(Grant No.2009CB939901)the Henan Provincial Science and Technology Research Project(Grant No.232102241016).
文摘To insight into the B-site ordering in RFe_(0.5)Cr_(0.5)O_(3)ceramics,a series of RFe_(0.5)Cr_(0.5)O_(3)ceramics(R=La,Y,Lu)were synthesized by the sol-gel method,and the structural and magnetic properties were systemically investigated.By using the Rietveld refinement of all samples,it is found that the structural distortion is increased as the R ionic radius decreases,leading to the weakened interactions between Fe/Cr ions.Moreover,the Fe and Cr are arranged in disorder in LaFe_(0.5)Cr_(0.5)O_(3),but partially ordered in YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3),showing an increasing trend of the proportion of ordered domains with the decrease of R ionic radius.Through fitting the temperature-dependent magnetizations,it is identified that the magnetization reversal(MR)in disorder LaFe_(0.5)Cr_(0.5)O_(3)is resulted from the competition between the moments of Cr and Fe sublattices.In the partially ordered YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3)ceramics,because of the presence of Fe-O-Cr networks in the ordered domains whose moment is antiparallel to that of Fe-O-Fe and Cr-O-Cr in the disordered domains,the compensation temperature T_(comp)of MR is increased by nearly 50 K.These results suggest that the changing of R-site ions could be used very effectively to modify the Fe-O-Cr ordering,apart from the structural distortion,which has a direct effect on the magnetic exchange interactions in RFe_(0.5)Cr_(0.5)O_(3)ceramics.Then at values of composition where ordered domains are expected to be larger in number as compared to disordered domains and with a weaker structural distortion,one can expect a higher transition temperature Tcomp,providing a different view for adjustment of the magnetic properties of RFe_(0.5)Cr_(0.5)O_(3)ceramics for practical applications.
基金Project supported by the National Natural Science Foundation of China(11504078)the Key Project of the Education Department of Guizhou Province(KY2015379)+1 种基金Joint Funds of Department of Science and Technology of Guizhou Province,Liupanshui Administration of Science and Technology and Liupanshui Normal University(LH[2014]7449,LH[2014]7456)Research Foundation for Advanced Talents of Liupanshui Normal University(LPSSYKYJJ201404)
文摘Lanthanum manganite with cation vacancies from nominal La（0.75）Sr（0.25）Mn（0.92）△（0.08）O（3-δ） nanocrystalline powder was successfully prepared at different calcination temperatures using the sol-gel method. X-ray diffraction shows that as the calcination temperature（T（Cal）） increases, the crystal particle diameter increases, but the B-site vacancy content decreases. According to a powder diffraction profile fitting technique and transmission electron microscopy results, the vacancy content can be estimated as 0.08,0.01, and 0.005 for T（Cal） = 1073,1273, and 1473 K, respectively. Magnetization versus temperature curves show that the magnetic transition temperatures, including the Curie temperature, are influenced by both B-site vacancies and double-exchange interaction between Mn^（3＋） and Mn^（4＋） cations. A core-shell model is proposed for vacancies located on the surfaces of the crystal particles. As an application, the magnetic moment angle θ（ij） between Mn^（3＋） and Mn^（4＋） cations on the surface, which decreases with decreasing vacancy content, can be obtained.
