EPR Spectra of Sintered Cd1−xCrxTe Powdered Crystals with Various Cr Content

In this paper, we show a simple method of producing ferromagnetic materials with a Curie temperature above room temperature. The electron paramagnetic resonance (EPR) spectra of Cd1−xCrxTe (0.002 < x < 0.08) were measured with a dependence on temperature (82 K < T < 381 K). Obtained EPR lines were fitted to a Lorentz-shaped curve. The temperature dependencies of the parameters of the EPR lines, such as the peak-to-peak linewidth (Hpp), the intensity (A), as well as the resonance field (Hr), were studied. Ferromagnetism was noticed in samples at high temperatures (near room temperature). For a sample with a nominal concentration of chrome of x = 0.05, a very strong intrinsic magnetic field is observed. The value of the effective gyromagnetic factor for this sample is ge = 30 at T = 240 K. An increase of chrome concentration above x = 0.05 reduces the ferromagnetic properties considerably. Analysis of the temperature dependencies of the integral intensity of EPR spectra was carried out using the Curie–Weiss law and the paramagnetic Curie temperature was obtained.

Электрическое сопротивление и магнитная восприимчивость сплавов CoFeSiBNb + REM при высоких температурах

Electrical resistivity and magnetic susceptibility of Co48Fe25Si4B19Nb4 + R (R = Nd, Sm, Tb, Yb) alloys in crystalline and liquid states were studied in present work. Electronic characteristics (effective magnetic moment, density of states at the Fermi level and paramagnetic Curie temperature) were calculated from experimental data. It is shown that all rare earth metals that were used should increase the glass-forming ability of alloys, but neodymium and samarium can have the greatest effect.

Magnetic and Mössbauer Studies on Mixed-Metal Cyano-Bridged Compounds GunM1.5-n[Fe(CN)6]·xH2O(M=Ni, Gu)

Mixed-metal cyano-bridged compounds GunM1.5-n[Fe (CN)6]·xH2O(M=Ni, Gu) have been prepared by co-precipitation. The magnetic results show that the compound Cu0.75Ni0.75[Fe (CN)6]·xH2O is ferromagnetic, undergoes a paramagnetic to the ferromagnetic transition temperature at 21.77 K. The paramagnetic curie temperature θ, residual magnetization Mr, and coercive field Hcare different from bimetallic Prussian Blue analogues Ni3[Fe (CN)6]2·xH2O and Cu3[Fe (CN)6]2· xH2O. As to Cu3[Fe (CN)6]2·xH2O, the magnetic susceptibilities follow the Curie-Weiss law and the Weiss paramagnetic Curie temperature is 19.1 K. The Mossbauer spectrum at room temperature reveals a doublet with the isomer shift parameter (-0.03 mm/s) and quadrupole splitting (QS= 1.09 mm/s). As the sample was cooled down to 16K, the magnetic splitting phenomenon was detected in the compound.

Anomalous Magnetism in Eu(Ca)B6

The transport and magnetic properties of the Eu1-xCaxB6 (0x0.4) single crystals were studied in the wide ranges of temperatures (1.8-300 K) and magnetic fields (up to 8 T). The experimental data allow to identify a metal-insulator transition (MIT) at the critical Ca concentration xMIT≈0.3, which agrees well with the predictions of double exchange model (V.M. Pereira et al. Phys. Rev. Lett., 93 (2004) 147202). A significant enhancement of magnetoresistive effect is observed below 100K for Eu1-xCaxB6 compounds corresponding to the metallic side of the MIT (xxMIT). The drastic decrease of paramagnetic Curie temperature evaluated from the magnetic and magnetotransport data is discussed in terms of quantum MIT scenario recently proposed for this low carrier density system.

MAGNETIC PROPERTIES OF CaxLa1 - xMnO3 (x > 0.5) PEROVSKITES

The magnetic properties of Ca x La 1 - x MnO 3 perovskites with x = 0.6 and x = 0.8 were studied in a large temperature range. A transition from mictomagnetic to antiferromagnetic state is evidenced at low temperatures for the samples with high lanthanum content. As the calcium content increases an essential antiferromagnetic behaviour is shown. The valences states of Mn ions were determined. The interactions inside the magnetic sublattices dominate those between the two sublattices as evidenced by the positive paramagnetic Curie temperature.

Magnetic properties of undoped and Co-doped n-type β–FeSi2.5 single crystals

Results of magnetization and magnetic susceptibility measurements on undoped and Co-doped FeSi2.5 single crystals are presented. The temperature dependence of the magnetic susceptibility of the Co-doped sample in the range of 5–300 K can be explained by temperature-dependent contributions due to paramagnetic centers and the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature and activation energy of the donor levels were estimated. It is also shown that the magnetic susceptibility of Co-doped samples cooled in zero external field and in a field are different. This resembles the properties of spin-glasses and indicates the presence of coupling between magnetic centers.

EPR AND MAGNETIC SUSCEPTIBILITY STUDIES OF V4+ IONS IN 2B2O3·SrO GLASS MATRIX

Electron paramagnetic resonance (EPR) and magnetic susceptibility studies on x V 2 O 5 ·(100 - x)[2 B 2 O 3 · SrO ] glasses with 0 ≤ x ≤ 30 mol% were performed. The covalence degree of vanadium bonds was estimated according to the LCAO-MO model. The EPR data show the presence of V4+ ions in a square-pyramidal coordination (C4v). The experimental EPR spectra are simulated assuming a superposition of two signals, one with hyperfine structure (HFS) typical for isolated ions and the other one consists of a broad line without HFS characteristic for clustered ions. These results are consistent with the magnetic data which indicate that for x ≥ 5 mol% V2O5 the temperature dependence of the reciprocal magnetic susceptibility is described by a Curie–Weiss type law with negative paramagnetic Curie temperature. The magnetic data also allow the estimation of NV4+ / Ntotal ratio.