Papers by Keyword: Ferrimagnetism

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Authors: Zhong Long Wang, Qiao Wu, Lin Jie Ding
Abstract: The finite-temperature magnetic properties of an antiferromagnetic (AF) bond alternating S=1/2 zigzag spin chain with asymmetrical AF next-nearest-neighbor (NNN) exchange interactions in an external magnetic field are investigated by means of the many-body Greens function theory within random phase approximation. The results show that when the NNN exchange interactions are asymmetrical, the spin system exhibit a clear ferrimagnetic ordering at finite temperatures. It is shown that the ferrimagnetic behavior is attributed to asymmetrical elementary excitations, resulting from the competition between the spin frustrations and magnetic excitations reduced by the asymmetrical NNN interactions. The mechanism of this ferrimagnetism is much different from a common one which originates from mixed spins with different spin values through antiparallel spin alignments.
4262
Authors: Qing Lin, Shao Hong Chen, Yun He, Xiao Gang Li, Hai Fu Huang
Abstract: The mixed valency character and antiferromagnetic coupling in Molecule magnets Materials NBu4FeIInMnII1-n[FeIII(OX)3](n=0.03、0.10、0.15、0.97) were investigated by magnetic measurements.The values of M increase and exhibit weak irreversibility in the field-cooled (FC) magnetization curves. There are a clear bifurcation phenomenon of the field-cooled (MFC) and Zero-field-cooled (MZFC) magnetization curves.In the Molecule magnets Materials NBu4FeII0.10 MnII0.90[FeIII(OX)3],the Ne´el temperature is 34 K.And the Ne´el temperature of NBu4FeII0.15MnII0.85 [FeIII(OX)3] is 28 K.In the sample NBu4FeII0.03 MnII0.97[FeIII(OX)3],,the bifurcation of the ZFC and FC plots below the Ne´el temperature of 30 K indicates irreversibility.The oxalate group has been shown to be an excellent bridging ligand in supporting the magnetic exchange interaction.
259
Authors: Viorel Sandu, Stelian Popa, Iuliana Pasuk, Ionut Enculescu, Mirela Sidonia Nicolescu, Simona Radicescu
Abstract: We present the preparation, structural, and magnetic properties of a series of Fe-containing borosilicate glasses as a function of the ratio SiO2/Fe2O3 which is ranging from 1.49 to 2.68. The role of nucleators (Cr2O3 and P2O5) was also investigated. X-Ray diffraction has revealed the formation of magnetite as the major or unique crystalline phase. As SEM micrographs have revealed, the addition of P2O5 give rise to a finer structure as compared with Cr2O3. In addition, the same oxide decreases the temperature of structural transition with almost 100 °C. The magnetization data reveal a two step transition at low temperatures: a high temperature transition at Tv = 128 K, which we attribute to the Verwey transition, and a low temperature transition at Ts = 48 K which, most likely, is the result of change in the dynamic of the domain motion.
445
Authors: Kawashita Masakazu, Masashi Tanaka, Tadashi Kokubo, Takeshi Yao, Sunao Hamada, Teruya Shinjo
645
Authors: Bruna da Costa Andrade, Marcelo Andrade Macedo
Abstract: A new W-type hexaferrite (Sr0.85Ce0.15Co2Fe16O27-δ) was synthesized through proteic sol-gel using coconut water as a solvent for the precursor salts. Structural analysis was carried out using an X-ray diffractometer (XRD). The XRD results showed that the resulting ceramic exhibited preferential orientations along the crystal planes in addition to lattice displacements. The magnetic properties evaluated using a vibrating sample magnetometer indicated a high saturation magnetization value and low coercive field and remnant magnetization values. The Curie temperature determined through differential scanning calorimetry was 473 oC. The electric resistivity value determined through complex impedance was similar to those already reported in the literature, thus promising the use of this hexaferrite in electronic and microwave device applications.
263
Authors: Katsuya Inoue, Ashot S. Markosyan, Hitoshi Kumagai, Prasanna S. Ghalsasi
449
Authors: Maria Elena Villafuerte-Castrejón, E. Castillo-Pereyra, A. Ayala-Morales, J. Tartaj, C. Moure, Pedro Durán, José Andrés Matutes-Aquino, L. Fuentes
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