metamagnetic behavior of linear chain pyridine compounds: Co(Pyridine)2Cl2, Fe(Pyridine)2Cl2, Fe(Pyridine)2(NCS)2 and Ni(Pyridine)2Cl2

Abstract

Magnetic phase transitions in the pyridine (pyr) compounds Co(pyr)2C12, Fe(pyr)2C12, Fe(pyr)2(NCS)2 and Ni(pyr)2C12 have been observed at applied magnetic fields of '-'0.7, 0.7, 1.1 and 2.7 kG respectively. These low field phase transitions are observed in the Fe and Ni compounds at T= 4.2 K, and in the Co compound at T< 3 K, and are consistent with metamagnetic behavior. Magnetic saturation is not achieved in any of these compounds for fields of 60 kG, reflecting high anisotropy.FEW magnetically ordered compounds show metaferromagnetic exchange, whereas the other four commagnetic phase transitions. Here we report the obserpounds exhibit ferromagnetic intrachain interactions. vation of low field, apparently metamagnetic, transitions in the pyridine (pyr) compounds Co(pyr)2C12, 1The temperature dependence of the magnetic Fe(pyr) 2C12 ,2 Fe(,pyr)2(NCS)2 ,~and Ni(pyr)2Cl2. susceptibility of Co(pyr)2Cl2 has been studied' in These compounds as well as Mn(pyr)2Cl2 4 and low applied fields (0.1-40 Oe) and the compoundS Cu(pyr) 2Cl2~5 '6have linear chain structureswith was shown to order antiferromagnetically with strong exchange interactions.along the chains, and TN = 3.17 K and with a parainagnetic Curie temperarelatively weak exchange interactions between chains. ture 0 + 5 K. A theoretical fit1 of the susceptibility The Mn and Cu compounds have intrachain antiwith a ferromagnetic Ising model yielded an intrachain interaction I/k = 11.7K. In Fig. 1(a) we plot the magnetic moment, a, as a function of applied magnetic field, H 0, for several selected temperatures . i both above and below the previously reported valuẽ TN =~. 17 K. The magnetic moment data were obtained with a vibrating sample magnetometer adapted to a superconducting solenoid. The data in Fig. 1(a) cover the range where the onset of long range

Antiferromagnetism and metamagnetism in 1,4-diazine and pyridine complexes of nickel(II)

“…1) and larger value of J (8 cm-', determined as described above). The magnetization data indicate a critical field, H,, of 2 kOe at 2 K for Ni(py)Cl,, a value much smaller than that in Ni(pyz)Cl, but similar to that reported for Ni(py),Cl, (52). This is consistent with the fact that, as in the latter compound, the antiferromagnetic interchain effects are mediated by non-bonding interactions.…”

“…The nickel ions are coupled ferromagnetically in chains via the bridging chloride ions and there is interchain antiferromagnetic coupling via bridging pyrazine ligands. Magnetic behaviour of this type is exhibited in a number of linear chain metamagnetic materials such as NiL,X, (X is C1 or Br and L is pyrazole or pyridine) (5 1) and M(py),Cl, (M is Co, Fe, or Ni) and Fe(py),(NCS), (52,53). Unlike the situation described for Ni(pyz)Cl,, however, in these complexes the interchain antiferromagnetism is mediated by non-bonding interactions.…”

Crystal Structure and Magnetic Behavior of the Decamethylferrocenium and Decamethylchromocenium Salts of Bis(ethylenedithiolato)nickel, [M(Cp*)2][Ni(edt)2] − Magnetic Anisotropy and Metamagnetic Behavior of [Fe(Cp*)2][Ni(edt)2]

“…At 55 kG the magnetization reaches a value of 1.95 Nµ B , and is not yet saturated, which is usual in metamagnetic materials if the temperature is not much lower than T N . [6,23] The high-field state is consistent with an FM state, where the saturation magnetization, M S ϭ g D S D ϩ g A S A ഠ 3 Nµ B , with S D ϭ S A ϭ 1/2, g D ϭ 3.95 (a tilting of 10°of the axis of the donor relative to the field was considered) and g A ϭ 2.06. For a ferrimagnetic state the expected value for the saturation magnetization M S ϭ g D S D Ϫ g A S A ഠ 0.91 Nµ B , is much smaller than the values obtained for the high-field state.…”

“…This behavior is very similar to that observed in other highly anisotropic compounds, such as the electron-transfer salts [Mn(Cp*) 2 ][M(tdt) 2 ] (M ϭ Ni, Pd, Pt) [6] or compounds with extended covalent networks such as M(pyr) 2 Cl 2 (M ϭ Co, Fe, Ni). [23] In order to study the magnetic anisotropy of compound 1, single-crystal measurements were performed on a SQUID magnetometer. Due to the needle-shaped form of the crystals two configurations were used for these measurements, one (L) with the applied field parallel to the axis of the crystals, which correspondes to a* and is relatively close to the stacking direction [101], making an angle of 5.65°.…”

Thiocyanato Coordination Polymers with Isomeric Coordination Networks – Synthesis, Structures, and Magnetic Properties

“…A similar behavior was observed for [Fe(NCS) 2 (pyridine) 2 ] n , which consists of the same Fe thiocyanato chains as those in 3-Fe/II. [57,[80][81][82] In this compound, the antiferromagnetic ordering is observed at 5.6 K for a DC field of 1000 Oe, and the critical field was determined to be 1200 Oe. [57] A similar behavior is also found for the 2D compound Fe(NCS) 2 [1,2-bis(4-pyridyl)ethylene], in which the thiocyanato chains are linked by the coligands into layers.…”