0000000000065968
AUTHOR
R. O. Kuzian
Magnetic susceptibility of multiferroics and chemical ordering
Magnetic susceptibility of two types of perovskite compounds A(Fe0.5M0.5)O3 A=Ba,Sr with M=Nb and Sb differing in the degree of chemical ordering was studied between 2 and 380 K. In the low temperature region, these compounds exhibit antiferromagnetic and spin-glass transition at T = 16−30 K. For the ordered compounds (M = Sb) the inverse susceptibility depends on T linearly up to the highest temperatures used. This enables the determination of the Weiss temperature θ and effective moment of the Fe3+ ion expressed by a number of Bohr magnetons, peff. In contrast to it, the compounds with M = Nb are characterized by a higher degree of the glassines and by a concave character of the inverse s…
Cluster superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics
We report the observation of cluster (local) superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature TC 7 K. Both the magnitude of this drop and TC decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below TC as well. The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and Meissner effect in metallic Pb nanoc…
Superspin glass phase and hierarchy of interactions in multiferroic PbFe1/2Sb1/2O3: an analog of ferroelectric relaxors?
We have fabricated new perovskite multiferroic PbFeSbO3 with a high degree (up to 0.9) of chemical ordering and unexpectedly high-temperature magnetic relaxor properties, which can barely be described within concepts of conventional spin glass physics. Notably, we found that the field-temperature phase diagram of this material, in the extremely wide temperature interval, contains the de Almeida–Thouless-type critical line, which has been the subject of long debates regarding its possible experimental realization. We explain our findings by the creation, at high temperatures of not less than 250 K, of giant superspins (SSs), owing, curiously enough, to the antiferromagnetic superexchange int…
Chemical disorder and Pb207 hyperfine fields in the magnetoelectric multiferroic Pb(Fe1/2Sb1/2)O3 and its solid solution with Pb(Fe1/2Nb1/2)O3
We report on the results of magnetic susceptibility, electron paramagnetic resonance, and $^{207}\mathrm{Pb}$ nuclear magnetic resonance (NMR) studies of the magnetoelectric multiferroic $\mathrm{Pb}(\mathrm{F}{\mathrm{e}}_{1/2}\mathrm{S}{\mathrm{b}}_{1/2}){\mathrm{O}}_{3}$ (PFS) ceramic, as well as its solid solution with $\mathrm{Pb}(\mathrm{F}{\mathrm{e}}_{1/2}\mathrm{N}{\mathrm{b}}_{1/2}){\mathrm{O}}_{3}$ (PFN) of different degrees of the 1:1 ordering of magnetic $\mathrm{F}{\mathrm{e}}^{3+}$ and nonmagnetic $\mathrm{S}{\mathrm{b}}^{5+}$ ions. The ordering has been studied by x-ray diffraction (XRD) and NMR methods. In particular, two spectral lines, originating from the ordered and dis…