摘要:

The magnetic properties of the radical salts formed by the organic donor bis-ethylenedithio-tetrathiafulvalene(in short ET) and magnetic polyoxoanions are presented. The used polyoxoanions are [XM(H2O)W11O39−11(X = Si, P; M = MnII, CrIII), with the Keggin structure and [CO4(H2O)2(PW9O34)2−10, where a ferromagnetic CoII4cluster is encapsulated by two trivacant Keggin fragments.

ISSN:1058-725X    

DOI:10.1080/10587259508031869

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this contribution, magnetic investigations on materials, which essentially combine mesogenic and polymeric properties, were presented. In the glassy and the smectic phase of a copper(II) containing polymer we observed remarkable antiferromagnetic exchange interactions between the copper centers, whereas in the isotropic phase, the magnetism followed the Curie-Weiss law. The monomeric model compound showed Curie-Weiss behaviour. In addition, we describe the magnetic behaviour of mesogenic compounds, resulting from the incorporation of rare-earth ions in chelating units of the liquid-crystalline Schiff base polymer.

ISSN:1058-725X    

DOI:10.1080/10587259508031870

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It has been found that the magnetic susceptibility of synthetic atacamite, Cu2Cl(OH)3, reveals existence of a relaxation phenomenon similar to that in the spin glass. The magnetic susceptibility shows an unusual behavior below 8K; there is a sharp peak in the magnetic susceptibility at about 5.3K when the crystal is cooled in zero magnetic field and the magnetization is a very slow process following a logarithmic law. On the other hand, the susceptibility decreases monotonously as the temperature is raised. The AC magnetic suscpeticibility x' shows a sharp peak at 5.8K, which shifts to higher temperature with increasing AC field frequency.

ISSN:1058-725X    

DOI:10.1080/10587259508031871

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Contrary to previous high field results, low field d.c. and a.c. magnetometry show that a number of the title compounds have 3D antiferromagnetic ground states and exhibit classical meta-magnetic behavior with critical fields ranging from 0.05 to 0.15 Tesla.

ISSN:1058-725X    

DOI:10.1080/10587259508031872

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The basic magnetism of new magnetic materials obtained by the mild condition metal ion insertion chemistry of inorganic high-spin iron III networks is highlighted.

ISSN:1058-725X    

DOI:10.1080/10587259508031873

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A variety of a.c. and d.c. magnetrometry data as well as iron-57 Mossbauer spectra show that the structurally layered divalent metal perrhenates: M(ReO4)2(M = Ni, Fe, Co) have three dimensional ferromagnetic ground states with Curie temperatures of 12.5K, 8.5K and 4.7K respectively. The nickel compound exhibits a substantial coercivity (∼ 0.26T) at 4.2K.

ISSN:1058-725X    

DOI:10.1080/10587259508031874

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

New experiments on a well known compound, a dodecanuclear manganese cluster of formula [Mn12O12(CH3COO)16(H2O)4, are providing very exciting results. Recently this cluster was shown to have a huge magnetic anisotropy of the Ising type which, associated to the large spin of the ground state, S=10, is responsible of an unusually slow relaxation of the magnetization. This, on its turn, is the origin of hysteretic behavior at low temperature. We have also looked at the relaxation properties in dilute frozen solutions of the cluster and we have found that the slow relaxation and hysteretic behavior persist, confirming that we are dealing with a molecular phenomenon. The large spin ground state associated with the king type anisotropy have also been evidenced in a different type of clusters of formula [Mn10(biphen)4O4Br124-recently synthesized, in which four manganese(III) and six manganese(II) are present and the spin of the ground state is 12.

ISSN:1058-725X    

DOI:10.1080/10587259508031875

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A structural and magnetic comparison is presented for a number of high nuclearity, higher oxidation state manganese complexes with similar ligation environments. The complexes considered are hepta-, octa-, ennea-, deca-, and dodecanuclear and contain only MnIII, except for the dodecanuclear complexes, which are mixed valence (MnIII8MnIV4). The ground state spins of these complexes range from very low to very high, and while the dodecanuclear complexes exhibit unusual AC magnetic susceptibility behavior, none of the other complexes show such properties. Magnetic properties, as well as structural and preparative information, are discussed.

ISSN:1058-725X    

DOI:10.1080/10587259508031876

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The mixed valence dodecanuclear complex [Mn12O12(O2CEt)16(H2O)3may be reduced by one electron to give (PPh4)[Mn12O12(O2CEt)16(H2O)4. Reduction of the complex occurs at one MnIIIion to give an unusual trapped-valence MnIIMnIII7MnIV4complex. This formulation is supported by X-ray crystallography at both low temperature and room temperature. DC (2.0–4.0K, 20–50 kG fields) and AC (2.0–30 K, 1.0 and 0.0050G fields, 25–1000 Hz frequencies) magnetic susceptibility measurements indicate ground states of S=9 and S=19/2 for the neutral and reduced species, respectively. (PPh4)[Mn12O122(O2CEt)16(H2O)4exhibits an out-of-phase component of the AC magnetic susceptibility (XM) which has a frequency dependent maximum. This is a very unusual property for a discrete molecular species to display. The neutral analog shows two peaks in theXMvs.Tplot. DC measurements also show the presence of prominent hysteresis loops, and field-cooled and zero-field-cooled magnetization data are not superimposed at low temperatures. The unusual magnetic relaxation properties persist even in polystyrene-doped samples of the complexes, indicating that this behavior arises from intramolecular rather than intermolecular properties.

ISSN:1058-725X    

DOI:10.1080/10587259508031877

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A magnetically active organometallic iron-Schiff base polymer, molecular weight was between about 4,000 and 50,000 daltons, was synthesized. This polymer comprised a multiplicity of Schiff base tridentate chelating groups having the capacity to combine with the iron (II) or iron (III) ion of an organic salt.

ISSN:1058-725X    

DOI:10.1080/10587259508031878

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor