Chromium acetylide complex based ferrimagnet and weak ferromagnet.
Chromium acetylide complex based ferrimagnet and weak ferromagnet.
复制标题
乙炔铬络合物基亚铁磁体和弱铁磁体。
作者：
J. Nishijo;K. Judai;Shigenori Numao;N. Nishi
报道了新型分子基磁体[CrCyclam（C[triple bond] C3-thiophene）（2）][Ni（mdt）（2）]（1）和[CrCyclam（C[triple bond]C-Ph）（2）][Ni（mdt）（2）]（H（2）O）（2）（Cyclam = 1，4，8，11-tetraazacyclotetradecane，mdt = 1，3-dithiole-4，5-dithiolate）的晶体结构和磁性。这两种化合物的晶体结构均由交替堆叠的[CrCyclam（C[三键]C-R）]（+）阳离子和[Ni（mdt）（2）]（-）阴离子的亚铁磁性链表征，链内交换相互作用为2 J = -6.1 K in 1和-5.7 K in 2（H = -2J Sigma（i）S（i）x S（i+1））。材料1在2.3 K时由于阳离子和阴离子之间的弱链间反铁磁相互作用而表现出亚铁磁转变。在2的情况下，相邻亚铁磁链中的阳离子被水分子桥接，导致链间反铁磁耦合。尽管2的整个晶体的中心对称性，一个桥接水分子仅占据两个中心对称位点中的一个，并且破坏相邻阳离子之间的局部中心对称性。由于2的局域对称性破缺引起的链间反铁磁相互作用和Dzyaloshinsky-Moriya相互作用在3.7 K时发生弱铁磁相变，矫顽力小于0.8 mT，随后在2.9 K时发生第二次磁相变。在此温度以下，矫顽力随着温度从2.9 K降低到1.8 K而从1 mT迅速增加到11.8 mT，而剩磁从3.6 K时的0.008 μ（B）单调增加到1.8 K时的0.12 μ（B）。
The crystal structures and magnetic properties of new molecule-based magnets, [CrCyclam(C[triple bond]C-3-thiophene)(2)][Ni(mdt)(2)] (1) and [CrCyclam(C[triple bond]C-Ph)(2)][Ni(mdt)(2)](H(2)O) (2) (Cyclam = 1,4,8,11-tetraazacyclotetradecane, mdt = 1,3-dithiole-4,5-dithiolate), are reported. The crystal structures of both compounds are characterized by ferrimagnetic chains of alternately stacked [CrCyclam(C[triple bond]C-R)](+) cations and [Ni(mdt)(2)](-) anions with intrachain exchange interactions of 2J = -6.1 K in 1 and -5.7 K in 2 (H = -2J Sigma(i) S(i) x S(i+1)). The material 1 exhibits ferrimagnetic transition at 2.3 K owing to weak interchain antiferromagnetic interactions between cations and anions. In the case of 2, cations in adjacent ferrimagnetic chains are bridged by a water molecule, resulting in an interchain antiferromagnetic coupling. Despite a centrosymmetry of a whole crystal of 2, one bridging water molecule occupies only one of the two centrosymmetric sites and breaks a local centrosymmetry between adjacent cations. The interchain antiferromagnetic interaction and Dzyaloshinsky-Moriya interaction originated from the local symmetry breakdown of 2 bring a weak-ferromagnetic transition at 3.7 K with a coercive force of less than 0.8 mT, followed by the second magnetic phase transition at 2.9 K. Below this temperature, the coercive force rapidly increases from 1 to 11.8 mT as the temperature decreases from 2.9 to 1.8 K, while the remanent magnetization monotonically increases from 0.008 mu(B) at 3.6 K to 0.12 mu(B) at 1.8 K.