Shuaikun Li,Yanhong Wang,Haibo Li,Hang Liu,Yun Lv,Hongcheng Lu
A novel magnetic alkaline-earth chromium fluoroiodate Ba 2 CrIO 3 F 6 has been successfully synthesized via the hydrothermal method and characterized for its structure and physical properties by single crystal X-ray diffraction, attenuated total reflection (ATR) infrared spectroscopy, UV-vis-NIR spectroscopy, thermal stability, as well as magnetic susceptibility, and specific heat. The compound Ba 2 CrIO 3 F 6 contains the [CrIO 3 F 6 ] 4- spin chains which are further separated by nonmagnetic Ba 2+ cations. The magnetic susceptibility results show no long-range magnetic order down to 2 K, which are further confirmed by specific heat measurement. The positive Weiss temperature and the increase of χT - T curve at low temperature both suggest the magnetic exchange interactions through the Cr 3+ −IO 4 F−Cr 3+ pathway are unexpectedly ferromagnetic. Our work illustrates that it is promising to use the IO x F y anion group for the design and construction of novel magnetic materials with ferromagnetic exchange interactions for potential spintronics device applications.
Hui Li,Shuang Li,Yanhong Wang,Yaling Dou,Hongcheng Lu
We prepared a layered antiferromagnet KNiB 4 O 6 F 3 1 by hydrothermal synthesis, and characterized its structure and physical properties by X-ray diffraction, magnetization and specific heat measurements as well as thermal stability, FTIR and UV–vis–NIR measurements. 1 consists of layers of composition [NiB 4 O 6 F 3 ] - separated by layers of K + cations. And Ni 2+ ions are arranged in slightly distorted triangular pattern in each [NiB 4 O 6 F 3 ] - layer. The magnetic susceptibility measurements indicate no divergence between the zero-field-cooled and field-cooled curves down to 7.9 K, below which a long-range order takes place as verified by specific heat measurements. The M ( H ) curve linearly increases when the field is weak (below ∼2 T), confirming that the ground state of 1 is antiferromagnetic. At 7 T, the magnetization of 1 is 1.67 μ B which is lower than the saturation magnetization.
Alimujiang Yalikun,Yanhong Wang,Nian Shi,Yiwen Chen,Hao Huang,Hyun-Joo Koo,Zhongwen Ouyang,Zhengcai Xia,Reinhard K. Kremer,Myung-Hwan Whangbo,Hongcheng Lu
We prepared a new polar layered quantum magnet Ba2Cu3(SeO3)4F2, by a combined use of F– and pyramidal SeO32– anions, determined its crystal structure by X-ray diffraction, and characterized its magnetic properties by magnetization, electron spin resonance (ESR) and specific heat measurements, and by density functional theory calculations. The title compound has first experimentally reported bitriangular chains of Cu2+ ions aligned along the b direction to form layers parallel to the ab plane, and these layers are separated by Ba2+ ions. The magnetic susceptibility data reveal that, despite strong predominant antiferromagnetic intrachain interactions indicated by the large negative Weiss temperature θ of −143.9 K within bitriangular chains, no long-range order occurs down to 2 K. The latter, further confirmed by the specific heat measurements, is attributed to the extremely weak interlayer interaction. The spins in each bitriangular chain become ferrimagnetically ordered to exhibit a 1/3-magnetization plateau, which persists at least up to 30 T. This reveals that each bitriangular chain acts as an S = 1/2 entity at low temperatures, as observed from the decrease of the effective magnetic moment Peff from 3.67 μB in the high temperature range to 1.89 μB in the low temperature range, equivalently, from three free Cu2+ ions to only one effective Cu2+ ion per formula unit. In each layer of Ba2Cu3(SeO3)4F2, the interaction between adjacent ferrimagnetic chains is ferromagnetic rather than antiferromagnetic, contrary to the observations in other reported cases.
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