Superparamagnetic-like behaviour in RE2WO6 tungstates (where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er)

The magnetization isotherms were used to study the superparamagnetic-like behaviour in polycrystalline (powder) RE2WO6 tungstates (where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er). The magnetization isotherms of the majority tungstates under study revealed both the spontaneous magnetic moments and hysteresis characteristic for the superparamagnetic-like behaviour with blocking temperature TB ¼ 30 K except the Sm2WO6 and Eu2WO6 compounds

Influence of Cr-substitution on the electrical properties of Fe1-xCrxVSbO6

Fe1xCrxVSbO6 solid solution is semiconductor with the activation energy decreasing both in the intrinsic and extrinsic conductivity temperature regions as the Cr-content increases. The n-type conduction is observed for Fe-richer samples while a change of the Seebeck coe cient (from n to p) for Cr-richer ones. Magnetic isotherms for all samples of solid solution under study are characteristic of the universal Brillouin function, indicating paramagnetic response. These e ects are discussed within the framework of the appearance of the mixed valence of both Fe and Cr ions

High spin-low spin transitions in Cu 0.2Co 0.76Cr 1.83Se 4 semiconductor

Magnetization, ac and dc magnetic susceptibility measured in the zero- eld-cooled mode were used to study the high spin low spin transitions in polycrystalline Cu0:2Co0:76Cr1:83Se4 semiconductor. The real part component of fundamental susceptibility ′ 1(T) and its second ( 2) and third ( 3) harmonics revealed two spectacular peaks at 128 K and at 147 K, con rming the appearance of the spin-crossover phenomenon.Magnetization, ac and dc magnetic susceptibility measured in the zero- eld-cooled mode were used to study the high spin low spin transitions in polycrystalline Cu0:2Co0:76Cr1:83Se4 semiconductor. The real part component of fundamental susceptibility ′ 1(T) and its second ( 2) and third ( 3) harmonics revealed two spectacular peaks at 128 K and at 147 K, con rming the appearance of the spin-crossover phenomenon

Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor

An antiferromagnetic order with a Néel temperature TN = 17:5 K, a strong ferromagnetic exchange evidenced by a positive Curie Weiss temperature CW = 77:3 K, the fuzzy peaks in the real component of susceptibility x′ (T) and the disappearance of the second critical eld were established. The curvature of speci c heat C(T) and C(T)=T in surrounding of TN indicated a broad peak, characteristic for the system with inhomogeneous magnetic state (spin-glass-like phase). The calculated magnetic entropy showed the value of S(T) 1 J/(mol K) which is extremely small; i.e., much lower than the magnetic contribution Rln(2S + 1) = 11:52 J/(mol K) calculated for the spin 3/2

Spin crossover in CuxCoyCrzSe4 semiconductors

Magnetization and magnetic susceptibility measured in the zero-field-cooled mode were used to study the spin crossover transition in polycrystalline CuxCoyCrzSe4 compounds. With increasing Co content a transition from ferromagnetic order via ferrimagnetic one to antiferromagnetic-like behaviour was observed. This transition is accompanied with a lowering symmetry from cubic to monoclinic and for the latter the spin crossover phenomenon occurs. These results are considered in a framework of the ligand–field split and the spin–orbit coupling

Influence of substitution of the chromium ions by the nonmagnetic Sb and Al ions on the magnetization processes in CuCr2X4 (X = S, Se) spinels

Both the dc and ac magnetic susceptibilities as well as magnetization measurements were used to study the influence of the dilution of the magnetic chromium subarray by nonmagnetic antimony and aluminium ions on the magnetization processes for four spinel families under investigation. Substitution of the chromium ions by the nonmagnetic Sb and Al ions in the compounds under study leads to the very hard magnetization in the case of the compounds with Sb and very easy magnetization in the compounds with Al. This effect is connected with the electronic configurations of the Sb and Al ions as well as with ionic radii of these cations

Molecular, spectroscopic, and magnetic properties of cobalt(II) complexes with heteroaromatic N(O)-donor ligands

New [Co(SCN)2(L)4/2] complexes, where L = b-pic (1), pyCH2OH (2), py(CH2)3OH (3), 1,2,4- triazolo[1,5-a]pyrimidine (4), [CoCl2(urotrop)2] (5), and [Co(DMIM)3]Cl2 H2O (6) where urotrop = hexamethylenetetramine and DMIM = 2,20-bis(4,5-dimethylimidazolyl) were synthesized in simple reactions of CoCl2 6H2O with ammonia thiocyanate and pyridine type ligands or urotropine and diimidazolyl ligands with cobalt(II) chloride in methanol solutions. The orthorhombic crystallization for (1), (2), and (4), the monoclinic one for (3) and (5) as well as the hexagonal one for (6) were found. The plots of the overlap population density-of-states indicated nonbonding character of the interactions between pyridine derivatives ligands and cobalt(II) ions in the complexes (1)–(4). The electronic spectra showed almost perfect octahedral complex in the case of (6). The magnetic susceptibility measurements revealed paramagnetic behavior with low values of the Curie–Weiss temperature, positive for complex (5) and negative for the other ones, although the transition to collective magnetic state at low temperatures for (4) and (5) was evidenced by an observation of antiferromagnetic coupling with Ne´el temperature of 4.5 K and the ferromagnetic one with Curie temperature of 10 K, respectively

Superparamagnetic-Like Behaviour in RE2\text{}_{2}WO6\text{}_{6} Tungstates (Where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er)

The magnetization isotherms were used to study the superparamagnetic-like behaviour in polycrystalline (powder) RE$\text{}_{2}$WO$\text{}_{6}$ tungstates (where RE = Nd, Sm, Eu, Gd, Dy, Ho and Er). The magnetization isotherms of the majority tungstates under study revealed both the spontaneous magnetic moments and hysteresis characteristic for the superparamagnetic-like behaviour with blocking temperature T$\text{}_{B}$ ≈ 30 K except the Sm$\text{}_{2}$WO$\text{}_{6}$ and Eu$\text{}_{2}$WO$\text{}_{6}$ compounds

ELECTRICAL CONDUCTIVITY OF THE MAGNETIC SPINEL SERIES Mn1-xCuxCr2S4

L'étude des propriétés électriques de la série des spinelles magnétiques concernée montre que la conductivité par trous augmente avec la température et la concentration en cuivre. Cet effet est relié au changement de valence des ions chrome de 3+ à 4+ et résulte du changement de conductivité de l'état semi-conducteur à l'état métallique. Un modèle de structure de bande, cohérent avec la transition de phase n-p dans MnCr2S4 est proposé.The study of the electrical properties of the magnetic spinel series under investigation shows that in this series hole conductivity increases with the increase of both temperature and Cu composition. This effect is connected with the change of valence of chromium ions from 3+ to 4+ and results in the change of the conductivity from a semiconductor to a metal. A band structure model consistent with the n-p phase transition in MnCr2S4 is proposed