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Ferromagnetic Transition (ferromagnetic + transition)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

Two Cobalt Compounds Based on Azide/Methoxy and Isonicotinate N -Oxide Ligands Exhibiting Ferromagnetic and Antiferromagnetic Interactions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2010
Fu-Chen Liu
Abstract Two new CoII complexes, [Co(OCH3)L] (1) and [Co3(N3)4(OCH3)2L2] (2) (L = isonicotinate N -oxide), were synthesized by solvothermal reaction and magnetically characterized. The cobalt ions in 1 and 2 all exhibit distorted octahedral coordination geometry. In 1, there is a ,11 -methoxy/syn,syn -carboxylate mixed coordinated cobalt chain with mixed coordination, and a 3D structure is formed by the chains linked through the L ligands. In 2, the alternating CoII chains that are formed by linking the double end-on azide-bridged trimers are connected by the L ligands to form a 2D layer. Magnetic studies revealed that ferromagnetic coupling exists between the CoII ions in 1, and 1 undergoes a ferromagnetic transition at 2.5 K, whereas alternating ferromagnetic (FM) and antiferromagnetic (AFM) interactions exist in the chain of 2. [source]

The metallographic cooling rate method revised: Application to iron meteorites and mesosiderites

METEORITICS & PLANETARY SCIENCE, Issue 1 2001
W. D. HOPFE
This revision incorporates a better fit to the ,/, + , phase boundary and to the ,/, + , phase boundary particularly below the monotectoid temperature of 400 °C. A reevaluation of the latest diffusivities for the Fe-Ni system as a function of Ni and P content and temperature is made, particularly for kamacite diffusivity below the paramagnetic to ferromagnetic transition. The revised simulation model is applied to several iron meteorites and several mesosiderites. For the mesosiderites we obtain a cooling rate of 0.2 °C/Ma, about 10x higher than the most recent measured cooling rates. The cooling rate curves from the current model do not accurately predict the central nickel content of taenite halfwidths smaller than ,10 ,m. This result calls into question the use of conventional kamacite growth models to explain the microstructure of the mesosiderites. Kamacite regions in mesosiderites may have formed by the same process as decomposed duplex plessite in iron meteorites. [source]

Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M = Mg, Co, Ni, and Zn)

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006
Kenji Yoshii
Abstract Magnetic and dielectric properties of the ruthenium double perovskites La2MRuO6 (M = Mg, Co, Ni, and Zn) were investigated. The magnetization measurements for M = Co and Ni showed the existence of magnetic order at 20,30 K. Though the oxides with M = Zn and Mg exhibit a deviation from the Curie,Weiss law, magnetic order was not clearly observed. The result of La2ZnRuO6 was different from that previously reported, in which a ferromagnetic transition was found at around 165 K. The AC dielectric measurements for M = Co and Ni showed large dielectric constants (typically larger than 1000) at around room temperature, suggesting both the formation of short-ranged polar regions and the magnetic origin of large dielectric constant. In addition, two peaks were found for the temperature dependence of the tan , component for La2NiRuO6. The behavior suggests the existence of two different polar regions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Antiferromagnetic-to-ferromagnetic transition induced by aluminum in the Ti(Fe1,xAlx)2 intermetallic compounds: a 57Fe Mössbauer spectroscopy study

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007
N. N. Delyagin
Abstract Mössbauer spectroscopy has been used to investigate the hyperfine field distributions and the local spin configurations of Fe atoms in the magnetically ordered Ti(Fe1,xAlx)2 compounds. The evolution of the spin arrangement of the Fe atoms was observed over the concentration range 0 , x , 0.25 at 5 K. The Al impurity suppresses the ferromagnetic exchange in the Fe(6h) layers and simultaneously provides the conditions for a transition of the Fe(2a) atoms, which are nonmagnetic in the TiFe2 compound, to the states with nonzero magnetic moment. The magnetic behavior of the Fe(2a) atoms is the key factor governing the anti- to ferromagnetic transition in the Ti(Fe1,xAlx)2 compounds. The magnetic ordering temperatures of the Ti(Fe1,xAlx)2 compounds were determined. In addition, the parameters of the electric-field gradient in TiFe2 as well as the relationship between the value of the magnetic moment of the Fe atom and the type of atomic configuration were discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Magnetotransport and magnetic properties of p -Zn1, xMnxTe:N , Carrier-induced ferromagnetism

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004
K.-T. Nam
Abstract The magnetic properties of nitrogen-doped p -Zn1, xMnxTe grown by MBE were studied through the magnetotransport measurements. In a sample of p -Zn1, xMnxTe with x = 0.034 and p = 4.7 × 1019 cm,3, a hysteresis loop was observed below 2.5 K in the Hall resistance and the magnetoresistivity, which indicates the ferromagnetic transition. From the plot of (RHall/Rsheet)2 against B/(RHall/Rsheet) at several temperatures, which corresponds to the so-called Arrott plot, we can estimate the Curie temperature (Tc) of the sample as about 3 K, suggesting that this sample has the higher Tc than ever reported. We also demonstrated, by means of light irradiation, that the strength of ferromagnetic interactions can be controlled by changing the hole concentration. An increase of the ferromagnetic behaviours such as a small increase of the coercive field was observed under light irradiation. This result strongly supports that the ferromagnetic transition in Zn1, xMnxTe is the carrier-induced one. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]