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Glasses of the xFe2O3 · (100 - x)[2B2O3 · SrO] system (0 ≤ x ≤ 40 mol%) were prepared and studied by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. EPR investigations indicated the compositional domains favorable to the presence of isolated iron ions or to those magnetically clustered. The magnetic susceptibility data evidenced the presence of both Fe3+ and Fe2+ ions, with their relative content depending on the Fe2O3 concentration. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample. [ABSTRACT FROM AUTHOR]

Glasses of the xFe2O3·(100–x)[3B2O3·KF] system, with 0

Glasses of the xMnO·(100–x)[Bi2O3·CdO] system with 0

The temperature dependence of the magnetic susceptibility of xFe[sub 2]O[sub 3]·(100-x)-[P[sub 2]O[sub 5]·CaO] glasses with 035 mol%, the evaluated values of the μ[sub eff] indicate either the presence of Fe[sup +] ions or the coordination influence on the magnetic moment of iron ions, but the presence of small quantities of the antiferromagnetic or ferrimagnetic interactions between iron ions in studied temperature range cannot be excluded. The high temperature susceptibility results indicate that the iron ions are isolated or participate in dipole-dipole interactions for glasses with x≤35 mol% and are antiferromagnetically coupled for higher contents of Fe[sub 2]O[sub 3]. [ABSTRACT FROM AUTHOR]

Glasses of the xFe[sub 2]O[sub 3]·(100-x) [3B[sub 2]O[sub 3]·KCl] system, with 0 < x ≤ 20 mol%, were investigated by means of EPR and magnetic susceptibility measurements. The Fe[sup 3+] ions in sites of distorted octahedral symmetry and clustered formations containing both Fe[sup 3+] and Fe[sup 2+] ionic species were verified. Dipolar and super-exchange interactions involving iron ions were revealed depending on the iron content of the sample. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) and magnetic susceptibility studies on xV[sub 2]O[sub 5]· (100 - x)[2B[sub 2]O[sub 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 V[sup 4+] ions in a square-pyramidal coordination (C[sub 4v]). 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% V[sub 2]O[sub 5] 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 N[sub V4+]/N[sub V[sub total]] ratio. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility studies have been done on χFe[sub 2]O[sub 3] · (100-χ)[3B[sub 2]O[sub 3] · BaO] glasses with 0 < χ ≤ 50 mol%. For χ ≤ 10 mol% it was shown that the glasses studied obey a Curie law and only Fe[sup 3+] ions are present, but for higher concentrations the magnetic susceptibility is described by a Curie-Weiss law and both Fe[sup 3+] and Fe[sup 2+] valence states, which participate in antiferromagnetic interactions, are evidenced. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) and magnetic susceptibility studies on χV[sub 2]O[sub 5] · (100 - χ)[2B[sub 2]O[sub 3] · SrO] glasses with 0 ≤ χ ≤ 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 V[sup 4+] ions in a square-pyramidal coordination (C[sub 4v]). 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 consisting of a broad line without the HFS characteristic for clustered ions. These results are consistent with the magnetic data which indicate that for χ ≤ 5 mol% V[sub 2]O[sub 5] 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 N[sub V[[sup 4+]]/N[sub V[sub total]] ratio. [ABSTRACT FROM AUTHOR]

EPR and magnetic susceptibility measurements have been performed on xFe[sub 2]O[sub 3] · (100 - x)[3B[sub 2]O[sub 3] · CaO] glasses with 0 < x ≤ 40 mol%. The Fe[sup 3+] ions in sites of distorted octahedral symmetry and clustered formations containing both Fe[sup 3+] and Fe[sup 2+] ionic species were found. Dipolar and magnetic super-exchange interactions involving iron ions were revealed to depend on the iron content of the sample. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility and electric resistivity measurements have been performed on xFe[sub 2]O[sub 3] · (100- x)[3B[sub 2]O[sub 3] · CaO] glasses with 0 < x ≤ 50 mol%. Magnetic susceptibility data suggest that for x > 5 mol% the iron ions participate in the negative superexchange interaction. From Curie constant values we have established that in these glasses both Fe[sup 2+] and Fe[sup 3+] ions are present, which explains their magnetic and electric behavior. The electrical resistivity and the conductivity activation energy decreases with the Fe[sub 2]O[sub 3] content. In order to analyze the electrical data, we have considered, in these glasses, a polaronic model for conduction. [ABSTRACT FROM AUTHOR]

Magnetic susceptibility and electric resistivity measurements have been performed on xMnO·(100 - x)[2B[sub 2]O[sub 3]·PbO] glasses with 0 < x ≤ 80 mol%. Magnetic data suggest that for x > 30 mol% the manganese ions experience negative magnetic super-exchange interactions. From Curie constant values we have established that in these glasses both Mn[sup 2+] and Mn[sup 3+] ions are present, which explains their magnetic and electric behaviour. The conductivity increases while the conductivity activation energy decreases with the MnO content. In order to analyse the conductivity data, we have considered in all glasses a polaronic model for conduction. [ABSTRACT FROM AUTHOR]