Karel Knížek

Structure and magnetic properties of Pr1−xSrxMnO3 perovskites

Abstract A comprehensive account of structural features in mixed Mn3+, Mn4+ perovskites, Pr1−xAxMnO3 (A = Ca, Sr, Ba) is given. The newly investigated Sr system was studied at various temperatures by X-ray and neutron diffraction, magnetic, and conductivity measurements. A low-temperature transition from the activated type to the degenerate type of conductivity was observed in the Sr system for x = 0.3–0.4. It occurs 20–60 K below the ferromagnetic Curie point.

Magnetic heating by cobalt ferrite nanoparticles

In the quest for suitable materials for hyperthermia we explored the preparation and properties of nanoparticles of Co ferrite. The material was produced by coprecipitation from water solution of Co and Fe chlorides and afterwards annealed at 400, 600 and 800 °C. The resulting particles were characterized by XRD, TEM, Mossbauer spectroscopy, and dc and ac magnetometry. The heating experiments in ac magnetic fields of various amplitudes were performed with diluted systems of particles suspended in agarose gel and the results were interpreted on the basis of the ac magnetic losses measured at various temperatures. The increase of magnetic losses and consequently of the heating efficiency with increasing temperature is explained by the strong dependence of the constant of magnetocrystalline anisotropy of Co ferrite on temperature.

Silica encapsulated manganese perovskite nanoparticles for magnetically induced hyperthermia without the risk of overheating

Nanoparticles of manganese perovskite of the composition La(0.75)Sr(0.25)MnO(3) uniformly coated with silica were prepared by encapsulation of the magnetic cores (mean crystallite size 24 nm) using tetraethoxysilane followed by fractionation. The resulting hybrid particles form a stable suspension in an aqueous environment at physiological pH and possess a narrow hydrodynamic size distribution. Both calorimetric heating experiments and direct measurements of hysteresis loops in the alternating field revealed high specific power losses, further enhanced by the encapsulation procedure in the case of the coated particles. The corresponding results are discussed on the basis of complex characterization of the particles and especially detailed magnetic measurements. Moreover, the Curie temperature (335 K) of the selected magnetic cores resolves the risk of local overheating during hyperthermia treatment.

Spin state of La Co O 3 : Dependence on Co O 6 octahedra geometry

The electronic structure of the rhombohedral

Electric transport and magnetic properties of perovskites LaMn1−xCoxO3 up to 900 K

\mathrm{La}\mathrm{Co}{\mathrm{O}}_{3}

Character of the excited state of the Co3+ ion in LaCoO3

perovskite is calculated for a number of structures with varying

On the magnetic properties of Gd implanted GaN

\mathrm{Co}{\mathrm{O}}_{6}

New chlorine‐substituted liquid crystals possessing frustrated TGBA and SmQ phases

octahedra geometry. The calculations are based on the generalized gradient approximation (GGA) to the density functional theory and, in order to describe better the strong electron-electron correlation in Co

Single-phase region of the 2212-BiSrCaCuO superconductor

3d

Distribution of cations in nanosize and bulk Co–Zn ferrites

states, the