Siebeneichler Stefanie, Dorn Katharina V, Smetana Volodymyr, Valldor Martin, Mudring Anja-Verena
Department of Materials and Environmental Chemistry (MMK), Stockholm University, Svante Arrhenius väg 16 C, 10691 Stockholm, Sweden.
Centre for Materials Science and Nanotechnology (SMN), Department of Chemistry, University of Oslo, Postbox 1033, Blindern 0315, Oslo, Norway.
J Chem Phys. 2020 Sep 14;153(10):104501. doi: 10.1063/5.0023343.
A new ionothermal synthesis utilizing 1-alkyl-pyridinium hexafluorophosphates [CPy][PF] (x = 2, 4, 6) led to the formation of highly crystalline single-phase ammonium cobalt trifluoride, (NH)CoF. Although ammonium transition-metal fluorides have been extensively studied with respect to their structural and magnetic properties, multiple aspects remain unclear. For that reason, the obtained (NH)CoF has been investigated over a broad temperature range by means of single-crystal and powder x-ray diffraction as well as magnetization and specific heat measurements. In addition, energy-dispersive x-ray and vibrational spectroscopy as well as thermal analysis measurements were undertaken. (NH)CoF crystallizes in the cubic perovskite structure and undergoes a structural distortion to a tetragonal phase at 127.7 K, which also is observable in the magnetic susceptibility measurements, which has not been observed before. A second magnetic phase transition occurring at 116.9 K is of second-order character. The bifurcation of the susceptibility curves indicates a canted antiferromagnetic ordering. At 2.5 K, susceptibility measurements point to a third phase change for (NH)CoF.
一种利用六氟磷酸1-烷基吡啶鎓盐[CPy][PF]（x = 2、4、6）的新型离子热合成方法，成功合成了高度结晶的单相三氟化铵钴（NH）CoF。尽管铵过渡金属氟化物在结构和磁性方面已得到广泛研究，但仍有多个方面尚不清楚。因此，通过单晶和粉末X射线衍射以及磁化强度和比热测量，在较宽的温度范围内对所得到的（NH）CoF进行了研究。此外，还进行了能量色散X射线和振动光谱以及热分析测量。（NH）CoF以立方钙钛矿结构结晶，并在127.7 K时发生结构畸变转变为四方相，这在磁化率测量中也可观察到，而此前尚未观察到这种现象。在116.9 K发生的第二次磁相变具有二级特征。磁化率曲线的分叉表明存在倾斜反铁磁有序。在2.5 K时，磁化率测量表明（NH）CoF发生了第三次相变。
