Nguyen Phuong-Hieu T, Milam-Guerrero JoAnna, Tran Gia T, Bloed Charles J, Neer Abbey J, Nguyen Anh, Gredig Thomas, Huq Ashfia, Lapidus Saul H, Melot Brent C, Derakhshan Shahab
Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, United States.
Department of Chemistry, University of Southern California, 3620 McClintock Ave., Los Angeles, California 90089-1062, United States.
Inorg Chem. 2020 Jun 1;59(11):7389-7397. doi: 10.1021/acs.inorgchem.9b03249. Epub 2020 May 9.
Two new transition metal oxides with the nominal chemical compositions of LiNiOsO and LiNiOsO were successfully synthesized. Both compounds crystallize in an ordered rock salt structure type in the monoclinic 2/ space group. The crystal structures were determined using both synchrotron X-ray and time-of-flight neutron, powder diffraction data. In both phases, Ni ions are present while oxidation states of osmium are +6 and +5 in LiNiOsO and LiNiOsO, respectively. Ni ions in the hypothetical fully ordered phase form a honeycomb arrangement in the crystallographic plane and these hexagons are centered by osmium ions. The magnetic layers are separated along the axis by the octahedra, which are centered by Li (or Li/Ni, depending on the chemical compositions). Crystal structure refinements reveal that there is some degree of mixed occupancy in cationic positions. Temperature dependent magnetic susceptibility data for both phases show ferrimagnetic transitions with predominant antiferromagnetic (AFM) interactions among 3d electrons of nickel and 5d electrons of osmium. Iso-thermal magnetization loops as a function of the applied magnetic field below the transition temperatures confirm the ferrimagnetic nature in magnetic transitions. Temperature dependent heat capacity data, however, did not exhibit any anomaly in either phase, indicating the absence of long-range magnetic ordering. The lack of long-range order for both Os and Os-based compounds was also confirmed by low temperature neutron diffraction data down to 10 K. Temperature dependent AC magnetic susceptibility data in various frequencies for both samples indicate that LiNiOsO exhibits spin-glass-like behavior, while the transition temperature for LiNiOsO is nearly frequency independent.
成功合成了两种标称化学组成为LiNiOsO和LiNiOsO的新型过渡金属氧化物。两种化合物均结晶为单斜2/空间群中的有序岩盐结构类型。使用同步加速器X射线和飞行时间中子粉末衍射数据确定了晶体结构。在两个相中，均存在Ni离子，而在LiNiOsO和LiNiOsO中，锇的氧化态分别为+6和+5。假设的完全有序相中的Ni离子在结晶平面中形成蜂窝状排列，这些六边形以锇离子为中心。磁性层沿轴被八面体隔开，八面体以Li（或Li/Ni，取决于化学成分）为中心。晶体结构精修表明阳离子位置存在一定程度的混合占据。两个相的温度依赖性磁化率数据显示出亚铁磁转变，镍的3d电子和锇的5d电子之间存在主要的反铁磁（AFM）相互作用。低于转变温度时，作为外加磁场函数的等温磁化回线证实了磁转变中的亚铁磁性质。然而，温度依赖性热容量数据在两个相中均未表现出任何异常，表明不存在长程磁有序。低至10 K的低温中子衍射数据也证实了两种基于Os和Os的化合物都缺乏长程有序。两个样品在不同频率下的温度依赖性交流磁化率数据表明，LiNiOsO表现出类似自旋玻璃的行为，而LiNiOsO的转变温度几乎与频率无关。
