Paramagnetic Susceptibility Measurements Research Articles

Magnetic properties of complex oxides Ba6Ni5 − x Mn x O15 (x = 2, 3, 4) of the A 3n + 3m A′ n B 3m + n O9m + 6n family

The magnetic interactions in the quasi-one-dimensional complex oxides Ba6NiMn4O15, Ba6Ni2Mn3O15, and Ba6Ni3Mn2O15 have been investigated using electron paramagnetic resonance and magnetic susceptibility measurements. It has been revealed that, for the Ba6Ni2Mn3O15 and Ba6Ni3Mn2O15 compounds, the magnetic moments are considerably smaller than the theoretical values and depend on the temperature. The results obtained have been interpreted under the assumption that the structure contains Ni3+ ions in which the energy level structure can lead to the above anomalies.

Thermal, structural and magnetic properties of some zinc phosphate glasses doped with manganese ions

(MnO) x ·(P 2O 5) 40·(ZnO) 60− x glasses containing different concentrations of MnO ranging from 0 to 20 mol% were prepared by the melt-quenching technique. The samples had a fixed P 2O 5 content of 40 mol% and the MnO:ZnO ratio was varied. The thermal, structural and magnetic properties of these glasses were investigated by means of differential thermal analysis (DTA), electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Compositional dependence of the glass transition ( T g), crystallization ( T p) and melting temperatures were determined by DTA investigations. From the dependence of the T g on the heating rate ( a), the activation energy of the glass transition ( E g) was calculated. The fragility index ( F) for the studied glasses was determined to see whether these materials are obtained from kinetically strong-glass-forming (KS) or kinetically fragile-glass forming (KF) liquids. The EPR spectra of the studied glasses revealed absorptions centered at g ≈ 2.0, 3.3 and 4.3. The compositional variations of the intensity and line width of these absorption lines was interpreted in terms of the variation in the concentration of the Mn 2+ and Mn 3+ ions in the glass and the interaction between the manganese ions. EPR and magnetic susceptibility data reveal that both Mn 2+ and Mn 3+ ions are present in the studied glasses, their relative concentration being dependent on the glass composition. Magnetic susceptibility data reveal an antiferromagnetic interaction between the manganese ions for the glasses containing 20 mol% MnO.

Influence of iron ions on the structural and magnetic properties of some zinc-phosphate glasses

Glasses in the (Fe 2O 3) x ·(P 2O 5) 40·(ZnO) 60− x (0 ≤ x ≤ 30 mol%) system have been prepared by the melt-quenching technique. The structural and magnetic properties of these glasses were investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The XRD pattern for the prepared samples shows their vitreous state only for x ≤ 20 mol%. For the samples containing 30 mol% Fe 2O 3 the presence of a unique crystalline phase, FePO 4, embedded in an amorphous matrix was evidenced. FTIR spectroscopy data suggest that the iron ions play the network modifier role in the studied glasses. The addition of iron oxide leads to the breakage of P O bonds and the formation of the P–O–Fe bonds. The presence of the Fe–O–P bonds for the samples with higher iron oxide content in the studied system improves their chemical durability. The increases of iron ions content of the samples determine a gradual decrease in the number of bridging oxygen ions respectively the increase of the number of non-bridging oxygen ions. EPR and magnetic susceptibility measurements show the presence of the Fe 3+ ions in sites of distorted octahedral symmetry and as well as in clustered formations containing both Fe 3+ and Fe 2+ ionic species. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample.

Electronic structural difference between Li7VN4 and Li7MnN4 due to the replacement of V with Mn: A simulation by a discrete variational Xα method

The difference in electronic structure of Li 7 M N 4 (M=V and Mn) due to the replacement of V with Mn is studied by the discrete variational (DV) X α method. Li 7 VN 4 and Li 7 MnN 4 crystallize in the same zinc-blende-like structure (space group: P-43n) with similar lattice constants of 9.6090 and 9.5548 Å, respectively. The DV-X α calculations show that Li 7 VN 4 is a semiconductor with energy gap between the empty V-3d related band and the completely occupied N-2p band, while Li 7 MnN 4 has a metallic electron configuration because of the partially occupied Mn-3d related band located above the completely filled N-2p band, exhibiting the shift of the Fermi level caused by an increase in electron due to the replacement of V with Mn, where Mn (electron configuration: 3d 5 4s 2 ) owns two more 3d electrons than V (3d 3 4s 2 ) does. Electron paramagnetic resonance and magnetic susceptibility measurements reveal that Li 7 MnN 4 is paramagnetic, resulting from the electrons partially occupying the Mn-3d related band, while Li 7 VN 4 is diamagnetic, arising from the un-occupation of the V-3d related band. These experiments support the computational results.

Intermediate (S = 1) spin state in five-coordinate cobalt(iii): Magnetic properties of N-o-hydroxy-benzamido-meso-tetraphenylporphyrin cobalt(iii), Co(N-NCO(o-O)C6H4-tpp)

The crystal structures of paramagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4),N(1),N(2),N(3),N(5),kappaO(2))cobalt(III) [Co(N-NCO(o-O)C(6)H(4)-tpp); 2] (S = 1) and diamagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4),N(1),N(2),N(3),N(5),kappaO(2)) gallium(III) chloroform.methanol solvate [Ga(N-NCO(o-O)C(6)H(4)-tpp).0.5CHCl(3).MeOH; 3.0.5CHCl(3).MeOH] (S = 0) were determined. The coordination sphere around Co(III) in 2 [or Ga(III) in 3.0.5CHCl(3).MeOH] is described as five-coordinate distorted trigonal bipyramid (DTBP) with O(1), N(1) and N(3) [or O(2), N(1), N(3)] lying in the equatorial plane for 2 [or 3.0.5CHCl(3).MeOH]. The magnitude of axial (D) zero-field splitting (ZFS) for the Co(III) (S = 1) in 2 was determined as approximately 107 cm(-1) by paramagnetic susceptibility measurements. The compound (2) reacts in donor solvent such as pyridine to form six-coordinate diamagnetic species of the type Co(N-NCO(o-O)C(6)H(4)-tpp)(py) (4), whose (1)H NMR spectra can be interpreted as for Co(III) in an octahedral environment.

Structural Variation and Magneto-Structural Correlation in Two New Dinuclear Bis(µ2-Phenoxo)-Bridged CuII Schiff-Base Complexes: Catalytic Potential for the Peroxidative Oxidation of Cycloalkanes

Two new dinuclear bis(μ2-phenoxo)-bridged copper(ii) complexes [Cu(NCS)L1]2 (1) and [Cu(NCS)L2]2 (2) have been synthesized using two tridentate NNO-donor Schiff-base ligands, L1H (Me2N(CH2)3N=CHC6H3(OMe)(OH)) and L2H (Me2N(CH2)3N=C(CH3)C6H4(OH)), respectively. They have been characterized by elemental analyses, IR, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-Ray single-crystal structures reveal a central Cu2O2 core in each complex with an isothiocyanate ligand coordinated terminally to each metal centre. The coordination environments around the CuII ions in 1 and 2 are a distorted trigonal bipyramid and a quasi-regular square pyramid, respectively, with significant differences in the Cu–O–Cu bridging angles (100.22(5)° for 1 and 95.64(7)° for 2). Although both CuII dimers present intradimer antiferromagnetic exchange interactions, the magnitudes of the coupling constants in 1 and 2 (J = –119(1) and –0.361(3) cm–1, respectively) are quite different as a result of the different coordination geometries and Cu–O–Cu bridging angles. Both complexes act as promising catalysts or catalyst precursors for the efficient peroxidative oxidation of cycloalkanes (cyclohexane and cycloheptane) to the corresponding cyclic alcohols and ketones, with maximum overall yields of 53% and 56% for 1 and 2, respectively.

Metal complexes of tetradentate and pentadentate N- o-hydroxybenzamido- meso-tetraphenylporphyrin ligand: M( N-NCO( o-OH)C 6H 4-tpp) (M = Zn 2+, Ni 2+, Cu 2+) and M′( N-NCO( o-O) C 6H 4-tpp) (M′ = Mn 3+) (tpp = 5, 10, 15, 20-tetraphenylporphyrinate)

The crystal structures of N- o-hydroxybenzimido- meso-tetraphenylporphyrinatozinc(II) toluene solvate [Zn( N-NCO( o-OH)C 6H 4-tpp)·C 6H 5CH 3; 4·C 6H 5CH 3], N- o-hydroxybenzimido- meso-tetraphenylporphyrinatonickel(II) chloroform solvate [Ni( N-NCO( o-OH)C 6H 4-tpp)·0.6CHCl 3; 5·0.6 CHCl 3], N- o-hydroxybenzimido- meso-tetraphenylporphyrinatocopper(II) toluene solvate [Cu( N-NCO( o-OH)C 6H 4-tpp)·C 6H 5CH 3; 6·C 6H 5CH 3] and N- o-oxido-benzimido- meso-tetraphenylporphyrinato(-κ 4,N 1,N 2,N 3,N 5,κO 2) manganese (III) methylene chloride·methanol solvate [Mn(N-NCO( o-O)C 6H 4-tpp)·CH 2Cl 2·MeOH; 8·CH 2Cl 2·MeOH] were established. The coordination sphere around Zn 2+ ion in 4·C 6H 5CH 3, (or Ni 2+ ion in 5·0.6 CHCl 3 or Cu 2+ ion in 6·C 6H 5CH 3) is a distorted square planar (DSP) whereas for Mn 3+ in 8·CH 2Cl 2·MeOH, it is a distorted trigonal bipyramid (DTBP) with O(1), N(1) and N(3) lying in the equatorial plane for 8·CH 2Cl 2·MeOH. The g value of 8.27 measured from the parallel polarization of X-band EPR spectra at 293 K is consistent with the high-spin mononuclear manganese(III) (S = 2) in 8. The magnitude of axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) in 8 was determined approximately as 3.0 cm −1 by the paramagnetic susceptibility measurements and conventional EPR spectroscopy.

Crystal lattice desolvation effects on the magnetic quantum tunneling of single-molecule magnets

High-frequency electron paramagnetic resonance (HFEPR) and AC susceptibility measurements are reported for a new high-symmetry Mn12 complex, [Mn12O12(O2CCH3)16(CH3OH)4].CH3OH. The results are compared with those of other high-symmetry spin S = 10 Mn12 single-molecule magnets (SMMs), including the original acetate, [Mn12(O2CCH3)16(H2O)4].2CH3CO2H.4H2O, and the [Mn12O12(O2CCH2Br)16(H2O)4].4CH2Cl2 & [Mn12O12(O2CCH2But)16(CH3OH)4].CH3OH complexes. These comparisons reveal important insights into the factors that influence the values of the effective barrier to magnetization reversal, Ueff, deduced on the basis of AC susceptibility measurements. In particular, we find that variations in Ueff can be correlated with the degree of disorder in a crystal which can be controlled by desolvating (drying) samples. This highlights the importance of careful sample handling when making measurements on SMM crystals containing volatile lattice solvents. The HFEPR data additionally provide important spectroscopic evidence suggesting that the relatively weak disorder induced by desolvation strongly influences the quantum tunneling interactions, and that it is under-barrier tunneling that is responsible for a consistent reduction in Ueff that is found upon drying samples. Meanwhile, the axial anisotropy deduced from HFEPR is found to be virtually identical for all four Mn12 complexes, with essentially no measurable reduction upon desolvation.

Magnetic Susceptibility and Ground-State Zero-Field Splitting in High-Spin Mononuclear Manganese(III) of Inverted N-Methylated Porphyrin Complexes: Mn(2-NCH3NCTPP)Br

The crystal structures of diamagnetic dichloro(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N'')-tin(IV) methanol solvate [Sn(2-NCH 3NCTPP)Cl 2.2(0.2MeOH); 6.2(0.2MeOH)] and paramagnetic bromo(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N'')-manganese(III) [Mn(2-NCH 3NCTPP)Br; 5] were determined. The coordination sphere around Sn (4+) in 6.2(0.2MeOH) is described as six-coordinate octahedron ( OC-6) in which the apical site is occupied by two transoid Cl (-) ligands, whereas for the Mn (3+) ion in 5, it is a five-coordinate square pyramid ( SPY-5) in which the unidentate Br (-) ligand occupies the axial site. The g value of 9.19 (or 10.4) measured from the parallel polarization (or perpendicular polarization) of X-band EPR spectra at 4 K is consistent with a high spin mononuclear manganese(III) ( S = 2) in 5. The magnitude of axial ( D) and rhombic ( E) zero-field splitting (ZFS) for the mononuclear Mn(III) in 5 were determined approximately as -2.4 cm (-1) and -0.0013 cm (-1), respectively, by paramagnetic susceptibility measurements and conventional EPR spectroscopy. Owing to weak C(45)-H(45A)...Br(1) hydrogen bonds, the mononuclear Mn(III) neutral molecules of 5 are arranged in a one-dimensional network. A weak Mn(III)...Mn(III) ferromagnetic interaction ( J = 0.56 cm (-1)) operates via a [Mn(1)-C(2)-C(1)-N(4)-C(45)-H(45A)...Br(1)-Mn(1)] superexchange pathway in complex 5.

EPR AND MAGNETIC SUSCEPTIBILITY STUDIES OF Gd3+ IONS-DOPED BISMUTH–GERMANATE GLASS MATRIX

Glasses of the x Gd 2 O 3 · (100-x)[4 Bi 2 O 3 · GeO 2] system, with 1 ≤ x ≤ 30 mol% were obtained and investigated by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The EPR spectra of the studied glasses reveal resonance sites with an unexpected high crystalline field in addition to the "U" spectrum, typical for Gd 3+ ions in glasses. This absorption line is due to Gd 3+ ions that replace Bi 3+ ions from the host glass matrix and can play former role of the unconventional network in the studied glasses. EPR and magnetic susceptibility data show that for low Gd 2 O 3 content, x ≤ 10 mol%, the Gd 3+ ions are randomly distributed in the host glass matrix and are present only as isolated species. For higher Gd 2 O 3 content, x > 10 mol%, the Gd 3+ ions appear as both isolated and antiferromagnetically coupled species.

STRUCTURAL AND MAGNETIC BEHAVIOR OF STRONTIUM-BORATE GLASSES DOPED WITH IRON IONS

Glasses of the x Fe 2 O 3 · (100 - x)[2 B 2 O 3 · 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 Fe 3+ and Fe 2+ ions, with their relative content depending on the Fe 2 O 3 concentration. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample.

Influence of iron ions on the magnetic properties of CaO–SiO 2–P 2O 5–Na 2O–Fe 2O 3 glass–ceramics

Room temperature Electron Paramagnetic Resonance (EPR) spectra and temperature dependent magnetic susceptibility measurements have been performed on 41CaO.(52− x)SiO 2.4P 2O 5. xFe 2O 3.3Na 2O ( 2 ≤ x ≤ 10 mol % ) glass–ceramics. The parent glass samples were prepared by quenching the homogenized melt from 1550 ∘C. The glasses were then heat-treated at 1050 ∘C for 3 h and slowly cooled to room temperature to yield glass–ceramics. EPR and high temperature magnetic susceptibility measurements were made to elucidate the state of Fe +3 ions in the glass–ceramics. The EPR absorption line centered at g ≈ 4.3 disappeared at higher concentrations of Fe 2O 3. The intensity and linewidth of the absorption line centered at g ≈ 2.1 increased as the Fe 2O 3 concentration was increased. Information about the structural changes involving iron ions, their valence state and type of magnetic interactions between the Fe ions was obtained using EPR and magnetic susceptibility measurements. The temperature dependence of the magnetization of the glass–ceramics with low Fe 2O 3 concentrations exhibit both ferrimagnetic and paramagnetic contributions. The results obtained have been used to understand the structural changes occurring in the vicinity of iron ions and the nature of magnetic interactions between the iron ions in these glass–ceramics.

EPR and Magnetic Susceptibility of Na2O–CuO–P2O5 Glasses

(50−x/2)Na2O–xCuO–(50−x/2)P2O5 glasses (x=1, 5, 15, or 30 mol%) have been prepared and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The shape of the Cu2+ EPR spectrum depends on the Cu content, and the corresponding computer simulations suggest that the Cu2+ ions occupy two different sites in these glasses: one of them is preponderant at low Cu content and the other is preponderant at high content, in which the Cu2+–Cu2+ interactions are more important. From EPR parameters, it was found that for the site at low content, the covalency of copper ion bonding with the surrounding ligands is appreciable. The magnetic susceptibility data appear to follow the Curie–Weiss law (χ=C/(T−θp)) with negative paramagnetic Curie temperature θp indicating antiferromagnetic interactions between Cu2+ ions that are more significant in the samples with high Cu content, in agreement with EPR results.

Paramagnetic defects and exchange coupled spins in pristine ultrananocrystalline diamonds

Electron paramagnetic resonance (EPR) and magnetic susceptibility measurements were done on nanodiamond samples fabricated by the detonation method and purified by acids. Comprehensive acid treatment leads to the reduction of EPR signals of magnetic impurities and revealing two weak and narrow EPR lines with g 1 = 4.26, ▵ H pp = 2.9 mT and g 2 = 4.00, ▵ H pp = 1.4 mT at T = 4 K, separated by the distance of 10.4 mT. The origin of this new doublet EPR signal observed in the well purified sample is discussed. The magnetic susceptibility behavior and doublet EPR signal ( g ∼ 4) suggest the weak antiferromagnetically exchange coupling of S = 1/2 paramagnetic defects as well as the presence of isolated dimers with S = 1.

EPR and magnetic susceptibility studies of B 2O 3–Bi 2O 3–Gd 2O 3 glasses

Glasses of the xGd 2O 3 · (100 − x)[B 2O 3 · Bi 2O 3] system with 0.5 ⩽ x ⩽ 10 mol% were studied by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Data obtained show that for low gadolinium oxide contents of the samples ( x ⩽ 3 mol%) the Gd 3+ ions are randomly distributed in the host glass matrix and are present as isolated and dipole–dipole coupled species. For higher gadolinium oxide contents of the samples ( x > 3 mol%) the Gd 3+ ions appear as both isolated and antiferromagnetically coupled species. The EPR spectra of the glasses reveal resonance sites with an unexpected high crystalline field in addition to the ‘U’ spectrum, typical for Gd 3+ ions in disordered systems. This absorption line is due to Gd 3+ ions that replace Bi 3+ ions from the host glass matrix and could play the network unconventional former role in the studied glasses.

Influence of Ni doping on vanadium oxide/hexadecylamine multiwall nanotubes

In this work, we present a characterization of a hybrid nanocomposite constituted by vanadium oxide (VO x )/ hexadecylamine (Hexa) and the effect of the addition of Ni ions on the magnetic properties. Micrographs of transmission electron microscopy (TEM) show that the nanostructures are multiwall nanotubes. The walls are constituted by the successive intercalation of VO x and Hexa layers. The number of vanadium atoms and the ratio Ni/V were measured by instrumental neutron activation analysis (INAA) and by energy dispersive spectroscopy (EDS), respectively. Measurements of electronic paramagnetic resonance (EPR) and DC magnetic susceptibility, as a function of temperature, reveal that the Ni doping reduces considerably the amount of V 4+ present in the system.

Structural and magnetic properties of(Fe0.93Ni0.07)2P

Structural and magnetic properties of(Fe0.93Ni0.07)2P havebeen investigated by means of powder x-ray and neutron diffraction, magnetization and paramagneticsusceptibility measurements over a temperature range of 10–500 K. The system crystallizes in theFe2P type hexagonal structure ( space group, Z = 3) in which the Ni atoms occupy the tetrahedralMI sites with total preference. Refined values of the cell parametersand bond distances are found slightly higher than those forFe2P and the atomic positional parameters are found quite close to those reported for the parent compoundFe2P. The temperature dependence of the magnetization shows a sharp magnetic phasetransition around 298(5) K. However there is difference of the zero-field cooled andfield cooled modes of the magnetization, which is indicative of the formation offerromagnetic clusters. The ferromagnetic to paramagnetic transition shifts towardsthe higher temperature side with increase in the applied magnetic field, whichindicates that the phase transition is a field induced type first-order magneticphase transition. There is no crystallographic structural transition associated withthe magnetic phase transition. The transition is caused by the change in thec/a ratio. The alloy retains the ferromagnetic order ofFe2P with the moments orienting along the [001] direction. The Rhodes–Wohlfarth ratio(µp/µs) of(Fe0.93Ni0.07)2P is foundto be 1.53 (>1), showing itinerant magnetism in this compound. At 297 K the magnetic moment at theMI site is found negligiblebut at the MII site itis ∼0.51 µB. The observednon-linearity above Tc in the χ−1–T curve gives clear evidence of the presence of short range magnetic order aboveTc. The momentsat the MII sites in the paramagnetic state and the exchange interactions are responsible forthe short range one-dimensional ferromagnetic chains along [001] well above theTc in(Fe0.93Ni0.07)2P.

Is neuromelanin changed in Parkinson’s disease? Investigations by magnetic spectroscopies

Human mesencephalic neuromelanin (NM) is characterized by an irregular, undefined structure, making its characterization by usual physico-chemical methodologies quite difficult. NM isolated from controls and from Parkinson's Disease (PD) patients was compared by high-resolution solid-state nuclear magnetic resonance (NMR). The pigment from PD patients appeared to be mainly composed of highly cross-linked, protease-resistant lipo-proteic material, with disappearance of melanin NMR resonances, suggesting melanin breakout due to oxidative stress conditions. Moreover, alpha-synuclein was detected in NM of PD patients and controls after cleavage of the melanin backbone under solubilizing conditions. NM stores iron ions as oxyhydroxide iron clusters containing thousands of iron atoms. Electron Paramagnetic Resonance (EPR) investigations and magnetic susceptibility measurements confirmed the occurrence of magnetic coupling among iron atoms, whereas in synthetic melanin the occurrence of isolated Fe(3+) ions was evident. NM from PD patients showed a lower total magnetization, possibly suggesting a progressive Fe migration from its storage environment (i.e., NM) to the cytosol.

Magnetic study of Cr 3+ ion in M2CrV 3O 11−x ( M[dbnd6]Zn, Mg) compounds

Electron paramagnetic resonance (EPR) and magnetic susceptibility measurements on the recently synthesized vanadates M 2CrV 3O 11− x ( M=Zn, Mg) have been analyzed. Two absorption lines with g≈2.0 (type I) and g ≈ 1.98 (type II) were recorded in the EPR spectra, which can be attributed to V 4+ ions and Cr 3+ ion clusters (pairs), respectively. The exchange constant J between Cr 3+ ions has been calculated, using both EPR and magnetic susceptibility data. Fitting of the EPR and magnetic susceptibility data has been carried out. The sign of J is a negative one for all samples and indicates antiferromagnetic interactions. Some difference in the J constant value among samples has been obtained. Volumetric titration confirms distinctly the presence of vanadium V 4+ ions in the investigated compounds.

Spectroscopic and magnetic behaviour of xGd 2O 3 (1 − x)(Bi 2O 3·PbO) glasses

Glasses of the xGd 2O 3 (1 − x)(Bi 2O 3·PbO) system (0 ≤ x ≤ 0.15) were obtained and studied by IR spectroscopy, electron paramagnetic resonance (EPR), magnetic susceptibility and density measurements. IR data show that increasing the amount of gadolinium ions in the studied glasses produces structural modifications of the host vitreous matrix consisting in a conversion of the [BiO 3] into [BiO 6] structural units. EPR and magnetic susceptibility data show that for low gadolinium oxide content of the samples, x ≤ 0.05, the Gd 3+ ions are randomly distributed in the host glass matrix and are present only as isolated species. For higher gadolinium oxide contents of the samples, x > 0.05, the Gd 3+ ions appear as both isolated and antiferromagnetically coupled species. IR and density measurements support the assumption of the network modifier role played by the gadolinium ions in the xGd 2O 3 (1 − x)(Bi 2O 3·PbO) glasses. EPR data show an unusual absorption line for the Gd 3+ ions in glass matrices. This absorption line is due to Gd 3+ ions that replace Bi 3+ and Pb 4+ ions from the host glass matrix and play the network former role in the studied glasses.