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Some layered phyllosilicates are characterized by spontaneous scrolling due to size mismatch between sublayers. The doping of layers by transition metal ions allows nanoscrolls to acquire magnetic properties. The magnetic behavior of synthetic (Mg1 –xCox)3Si2O5(OH)4 (x = 0.2, 0.4, 0.6, 0.8, 1) phyllosilicates with the chrysotile structure before and after partial hydrogen-induced reduction is studied. The dominant ferromagnetic behavior has been revealed in all studied phyllosilicates. Ensembles of cobalt metal nanoparticles in a silicate matrix have demonstrated a collective magnetic response at room temperature with a narrow hysteresis loop and fast saturation. [ABSTRACT FROM AUTHOR]

The authors study the formation of crystals of Fe-Ga oxides and Fe–Ga–Cu borates in a multicomponent flux system based on Bi2Mo3O12–Na2B4O7. The Curie–Weiss temperature (θCW = 289 K) and the temperature of the ferrimagnet–paramagnet phase transition (TC = 288 K) are determined from the electron spin resonance (ESR) spectrum and the magnetization of an Fe1.1Ga0.9O3 single crystal, depending on temperature. Lines of spin-wave resonance are observed in the spectrum of magnetic resonance in the ordered phase. [ABSTRACT FROM AUTHOR]

A double perovskite Sr2CrNbO6 powder compound was studied by using X-ray diffraction, AC and DC magnetization, and ESR measurements. Two transitions in antiferromagnetically ordered regimes were observed through magnetization measurements at T = 5 and 2 K and were confirmed by the linear dependence of the magnetization on the applied magnetic field at these temperatures, approximations of the temperature dependence of the ESR linewidth, and AC magnetization. The zero field cooling curve was approximated by Bonner–Fisher law for quasi one dimensional chain with the exchange integral J/kB = 1 K between chromium spins. An approximation of linear part of magnetic susceptibility temperature dependence was performed using Curie–Weiss law. To describe the obtained effective moment μeff = 3.577μB, the presence Cr3+ and Cr4+ ions is estimated at a respective ratio about 0.8 : 0.2. [ABSTRACT FROM AUTHOR]

A double perovskite Sr2CrNbO6 powder compound was studied by using X-ray diffraction, AC and DC magnetization, and ESR measurements. Two transitions in antiferromagnetically ordered regimes were observed through magnetization measurements at T = 5 and 2 K and were confirmed by the linear dependence of the magnetization on the applied magnetic field at these temperatures, approximations of the temperature dependence of the ESR linewidth, and AC magnetization. The zero field cooling curve was approximated by Bonner–Fisher law for quasi one dimensional chain with the exchange integral J/kB = 1 K between chromium spins. An approximation of linear part of magnetic susceptibility temperature dependence was performed using Curie–Weiss law. To describe the obtained effective moment μeff = 3.577μB, the presence Cr3+ and Cr4+ ions is estimated at a respective ratio about 0.8 : 0.2. [ABSTRACT FROM AUTHOR]

EPR spectra of impurity Ho3+ ions in oriented SrY2O4 single-crystals are registered at the temperature 4.2 K in the frequency range from 70 to 180 GHz. The results of measurements evidence for the substitution of Ho3+ ions for the Y3+ ions at the structurally nonequivalent sites R1 and R2 with the local Cs point symmetry. The values of g-factors, hyperfine structure constants and the energy gaps between the ground and the first excited non-degenherate crystal-field sublevels of the ground 5I8 multiplet are determined. The observed specific features of the ground states of Ho3+ ions (non-Kramers doublets with the zero-field splittings of 4.30 and 1.67 cm–1) open a possibility to identify transitions in optical spectra of SrY2O4:Ho and inelastic neutron scattering spectra of SrHo2O4 crystals. [ABSTRACT FROM AUTHOR]

The double perovskite Sr2TiMnO5.87 was synthesized via the solution combustion precursor method using Sr(NO3)2, MnO2, i-Ti(OC3H7)4, and disubstituted ammonium citrate as a complexing agent. The crystal structure and unit cell parameters are refined by the Rietveld method using powder X-ray diffraction. The magnetic properties of double perovskites Sr2TiMnO5.87 were studied using the ESR spectroscopy, specific heat measurements in the temperature range ~ 5–300 K, and magnetometry under cooling in zero- (ZFC) and nonzero-fields (FC). The four ESR line were observed in ESR spectra, three ESR lines with g ~ 2 and fourth ESR at Bres = 50 mT in both X-and Q-bands measurements in the temperature range 37.5–42 K in Sr2TiMnO5.87. The peaks obtained in real and imaginary parts of AC magnetization measurements confirm phase separation at the same temperatures. The antiferromagnetic ordering was found out below the temperature TN ≈ 12 K. The fitting Debye and Einstein temperatures, obtained from the specific heat measurements, are equal to θD = 217 K, θE1 = 275 K, θE2 = 615 K, and θE3 = 2000 K. [ABSTRACT FROM AUTHOR]

A study is performed of the magnetic and dielectric properties of Sr2MnTiO5.87 double perovskite. The origin of the magnetic phase transitions observed in the FC and ZFC magnetization and magnetic specific heat curves at 12 and 43 K is discussed. The Debye and Einstein temperatures, determined by analyzing the lattice contribution to the specific heat, are found to be θD = 217 K, θЕ1 = 275 K, θЕ2 = 615 K, and θЕ3 = 2000 K. [ABSTRACT FROM AUTHOR]

Low-temperature electron paramagnetic resonance measurements are performed on single crystals of LiY1 ‒xGdxF4 with low and moderate concentration of Gd ions. Modeling of the experimental spectra allows us to precisely determine microscopic parameters of the spin Hamiltonian of the parent LiGdF4 material, including the nearest-neighbor exchange constant. The obtained parameters are further tested by comparing a strongly anisotropic Curie–Weiss temperature obtained for LiGdF4 in our static magnetization measurements with theoretically computed values. We find a fine balance between principal magnetic interactions in LiGdF4, which results in a hidden magnetic frustration presumably leading to a delayed magnetic ordering and an enhanced magnetocaloric effect at low temperatures. [ABSTRACT FROM AUTHOR]

A FeCr2O4 single crystal with the spinel structure is grown by the zone melting method with optical heating. The critical temperatures of establishing the orbital ordering TOO = 138 K, the formation of the collinear ferrimagnetic state TN = 65 K, and the formation of the spiral modulation of the magnetic structure Ts = 38 K are determined from the temperature dependences of the heat capacity and magnetic susceptibility. An anomaly of the susceptibility at T ~ 21 K, below which the hysteresis curves become butterfly-like is probably caused by a change in the magnetic anisotropy. It is established that the magnetic resonance spectrum in the microwave X-band (~9.4 GHz) at T = 30 K changes under the reversal of the direction of the external magnetic field (nonreciprocity phenomenon). Magnetic and induced electric dipole transitions are considered theoretically. The detected nonreciprocity is explained by the interference of these transitions. [ABSTRACT FROM AUTHOR]

The magnetic and electronic properties of quasi-one-dimensional iron chalcogenide compound KFeS2 have been calculated within two DFT + U approaches based on the simplified LSDA + U approach and rotationally invariant LSDA + U approach. It is shown that the simplified LSDA + U approach with the single parameter correctly describes the magnetic ground state but erroneously predicts the electronic properties. On the other hand, the rotationally invariant LSDA + U approach with two independent parameters U and J provides the correct description of electronic and magnetic properties of KFeS2 at once. By the comparison of ab initio results with experimental data on magnetic ground state and electronic properties, the values of the parameters U and J have been proposed for the correct description of physical properties of KFeS2 within the DFT + U approach. [ABSTRACT FROM AUTHOR]

The magnetic and electronic properties of quasi-one-dimensional iron chalcogenide compound KFeS2 have been calculated within two DFT + U approaches based on the simplified LSDA + U approach and rotationally invariant LSDA + U approach. It is shown that the simplified LSDA + U approach with the single parameter correctly describes the magnetic ground state but erroneously predicts the electronic properties. On the other hand, the rotationally invariant LSDA + U approach with two independent parameters U and J provides the correct description of electronic and magnetic properties of KFeS2 at once. By the comparison of ab initio results with experimental data on magnetic ground state and electronic properties, the values of the parameters U and J have been proposed for the correct description of physical properties of KFeS2 within the DFT + U approach. [ABSTRACT FROM AUTHOR]