Search

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]

Magnetic properties of polycrystalline La0.81Sr0.19Mn0.9Fe0.1−xZnxO3 (x = 0, 0.05) have been investigated by means of electron spin resonance, magnetic susceptibility, and Mössbauer measurements. Both samples show a clear ferromagnetic transition. The Curie temperature TC decreases on increasing Fe content (x = 0.05—TC = 222 K; x = 0—TC = 148 K). Mössbauer studies indicate that Fe in these compounds is in the trivalent high-spin state. The temperature evolution of the Mössbauer spectra at low temperatures (T < TC) is typical for ferromagnetic clusters with a wide distribution in size and magnetic correlation length. The inverse susceptibility of all the samples deviates from the Curie–Weiss law above TC, indicating the presence of fluctuations on approaching magnetic order. An anomalous downturn of the inverse susceptibility for x = 0.05 significantly above TC and the concomitant observation of ferromagnetic resonance signals coexisting with the paramagnetic resonance up to approximately room temperature, is caused by a Griffiths-like behavior. This regime is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase. [ABSTRACT FROM AUTHOR]

The scandium orthosilicate monocrystal Sc228SiO5 (SSO) doped with 51V isotope in small concentrations (0.005% at.) was studied. We used continuous wave (CW) and pulsed electron spin resonance (ESR) methods with frequencies in the X-band range (9.3–9.8 GHz). From the orientational dependencies of the CW ESR spectra we found the following: the hyperfine interaction of the vanadium ions is very anisotropic and the Zeeman interaction is almost isotropic with principal values of the g – tensor near electron g – factor. In addition to that, we found that the charge state of vanadium ions is V4+. The directions of the principal axes of the A and g tensors were determined. The phase memory and spin–lattice relaxation were measured. It was found that the temperature dependence of the spin–lattice relaxation time can be approximated by the sum of direct and Aminov–Orbach processes with decent accuracy. The phase memory time stays in the microseconds range even at the temperature T = 30 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]

The temperature dependencies of the spin–lattice relaxation time and the phase relaxation time of 53Cr3+ ion in the Y228SiO5 single crystal are measured at the anti-crossing point via pulsed electron paramagnetic resonance technique at X-band frequencies and in the temperature range from 5 to 80 K. It is found that the phase relaxation time does not change rapidly near the anti-crossing point, whereas in optical experiments with rare-earth ions, the phase relaxation time decreases significantly with a slight deviation of the magnetic field from the anti-crossing point. The effect of spin dynamical decoupling on the phase relaxation time is measured using the Carr–Purcell–Meiboom–Gill (CPMG) multi-pulse sequence. [ABSTRACT FROM AUTHOR]

Monoisotopic 53 Cr 3 + impurity ions in scandium orthosilicate single crystal ( Sc 2 SiO 5 ) are studied by the method of electron paramagnetic resonance in the X-band frequencies. The directions of the main principal magnetic axes and the parameters of the effective spin Hamiltonian that describe the magnetic characteristics of the impurity centers of chromium, which replaces scandium in two structurally nonequivalent positions, are determined. It is shown that the orientation dependencies of the EPR spectra are well described by the second-order spin Hamiltonian corresponding to the orthorhombic symmetry of the local crystal field acting on the impurity ion. It was assumed that the g-tensor and the A-tensor determining the Zeeman energy of electronic levels in a magnetic field and the hyperfine interaction of electron and nuclear spins are isotropic, and the entire anisotropy of the EPR spectra is due to the anisotropy of the D-tensor, which describes the fine structure of electronic levels in a crystalline electric field. A strong dependence of the probability of "forbidden" transitions between hyperfine sublevels of electronic levels on the orientation of an external magnetic field is established. Moreover, for some orientations, the probability of "forbidden" transitions exceeds the probability of "allowed" transitions. [ABSTRACT FROM AUTHOR]

Abstract: The object of the investigation was n-type mercury chalcogenide (Mn0.11Hg0.89Te) monocrystal which was grown by crystallization from a two-phase mixture with replenishment of the melt from a tellurium solution. The investigations of microwave absorption derivative (dP/dH) showed the existence of strong high and low frequency oscillations in the magnetic field in the temperature range 4.2-20 K. The concentration and effective mass of charge carrier were determined from oscillation period and temperature dependence of oscillation amplitude. [ABSTRACT FROM AUTHOR]