Magnetic Study of the Low-Temperature Anomalies in the Optimally Doped PrBCO Compound
The anomalous magnetic properties of a nonsuperconducting PrBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+</sub> <inline-formula><tex-math notation="LaTeX">$_{x}$</tex-math></inline-formula> (or PrBCO) compound in an optimally doped oxygen state of concentration (<inline-formula><tex-math notation="LaTeX">$x= {\text{0.95}}$</tex-math> </inline-formula>) are investigated at low temperatures using magnetic measurements such paraprocess magnetic susceptibility <inline-formula><tex-math notation="LaTeX">$\chi _{{\text{H}}}(T)$</tex-math></inline-formula> under different values of a DC magnetic field <italic>H</italic> up to 8 T and isothermal magnetizations <inline-formula> <tex-math notation="LaTeX">$M_{{\text{T}}}(H)$</tex-math></inline-formula> with <italic>H</italic> up to 2.1 T. The temperature dependences of the derivatives of <inline-formula><tex-math notation="LaTeX">$\chi _{{\text{H}}}(T)$ </tex-math></inline-formula> indicate a significant decrease with increasing <italic>H</italic> of the Néel temperature <inline-formula><tex-math notation="LaTeX">$T_{{\text{N}}}= {\text{14}}\,{\text{K}}$</tex-math> </inline-formula> associated with antiferromagnetic (AFM) Pr ordering. The AFM-paramagnetic phase transition remains well defined even at 8 T, whereas the small anomaly at <inline-formula><tex-math notation="LaTeX">$T_{2}= {\text{10.5}}\,{\text{K}}$</tex-math></inline-formula>, which is due to the spin reorientation phase transition already reported before, seems clearly highlighted at 2 T but entirely suppressed above 6 T. A weak ferromagnetic (WFM) contribution is revealed below <inline-formula><tex-math notation="LaTeX">$T_{{\text{N}}}$</tex-math> </inline-formula> with more evidence particularly below the low critical point <inline-formula> <tex-math notation="LaTeX">$T_{{\text{cr}}}= {\text{4-5 K}}$</tex-math></inline-formula> whose anomaly is still visible with increasing <italic>H</italic> up to 8 T. Weak field-induced transitions between AFM and WFM phases are observed in the derivatives of <inline-formula><tex-math notation="LaTeX">$M_{{\text{T}}}(H)$</tex-math></inline-formula> at a low transition field (<inline-formula><tex-math notation="LaTeX">$H_{{\text{t}}}< {\text{1}}\,{\text{T}}$</tex-math> </inline-formula>). All results are discussed and compared with those found in previous works.
PSEUDODIPOLAR INTERACTION IN NONCOLLINEAR ANTIFERROMAGNETS AND SPIN WAVES IN PR2CUO4
Abstract There are tetragonal noncollinear antiferromagnets with sublattices which do not interact in the mean field exchange approximation (R2CuO4 family ( R = Pr, Nd, Sm, Eu ) U2Pd2X ( X = Sn, In ) PrBa2Cu3O6+x, etc.) Their noncollinear magnetic structure is explained assuming the pseudodipolar interaction (PDI). The spin waves of the copper subsystem in the R2CuO4 family are studied theoretically. The interplane PDI splits in-plane spin waves on acoustic and optical branches and the intraplane PDI gives rise to the in-plane spin-wave gap as a consequence of the interaction between spin waves. Neutron scattering data on Pr2CuO4 are presented and parameters of both intraplane and interplane PDI are determined. An analysis of the spin configuration in a canted magnetic field for R2CuO4 magnets is given and experimental evidence of the Bose–Einstein condensation of the uniform spin waves is presented.
Image Projection in Immersive 3D Visualization Laboratory
In recent years, many centers in the world attempted to build a virtual reality laboratory. The main idea of such laboratory is to allow the user to “immerse” into and move in a computer-generated virtual world. In the paper, the underlying principles of the system of virtual reality (VR) are described. The selected implementations constructed by the research centers of the world are also presented. The cave automatic virtual environment (CAVE) installation is planned to be implemented at the Gdansk University of Technology. In this solution, the images will be projected on flat screens arranged in the form of a cube. The user will be located inside a transparent sphere freely rotating inside a cube, which allows simulation of free movement without changing the position of the screens. A walking motion of the user will trigger changes in the computer-generated images on screens surrounding the sphere thus creating an illusion of motion. The problems of visualization in the planned installation are outlined and discussed.