Enhanced exchange bias effect in size modulated Sm0.5Ca0.5MnO3 phase separated manganite Magnetic properties and magnetocaloric effect of La0.8Ca0.2MnO3 nanoparticles tuned by particle size Origin of low temperature memory and aging effects in spin glass like La 0.7 Ca 0.3 MnO 3 nanomanganite Magnetic and structural properties of nanocrystalline low-doped La 0.8 Ca 0.2 CoO 3 cobaltites with particle size of 8, 13, 23, and 50 nm, prepared by the glycine-nitrate method, were investigated in temperature range 5-320 K, magnetic field up to 50 kOe and under hydrostatic pressure up to 10 kbar. With particle downsizing, a noticeable expansion of unit cell, with concomitant changes in the rhombohedral structure toward the cubic one was observed. It was found that the increased surface-disorder effect strongly suppresses the ferromagnetic state in La 0.8 Ca 0.2 CoO 3 nanoparticles leading to a decrease, by factor of about 2, both in spontaneous magnetization, M S , and Curie temperature, T C , when particle's size decreases from 23 to 8 nm. The effective magnetic moment eff was found also to decrease distinctly due to the strong interdependence between Co-O-Co interactions and Co spin state. The size-induced magnetic disorder drives the La 0.8 Ca 0.2 CoO 3 nanoparticles to a dominant glassy behavior for 8 nm particles. This is evidenced by the fact that the freezing temperature varies with magnetic field in a strict conformity with the de Almeida-Thouless law for spin glasses and also by the observation of characteristic slowing down in the spin dynamics. The applied pressure suppresses T C , M S , and coercive field H C , like it is observed for bulk La 0.8 Ca 0.2 CoO 3 . Nevertheless, in nanoparticles the pressure effect on T C is noticeably stronger, while H C diminishes with pressure much slower then in bulk material.

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The exchange-bias (EB) effect with sign reversal was found in LuFe 0.5 Cr 0.5 O 3 ferrite-chromite, which is a weak ferrimagnet below T N = 265 K, exhibiting antiparallel orientation of the ferromagnetic (FM) moments of the Fe and Cr sublattices due to opposite sign of the Fe-Cr Dzyaloshinskii vector, as compared to that of the Fe-Fe and Cr-Cr. The weak FM moments of the studied compound compensate each other at temperature T comp = 230 K, leading to the net magnetic moment reversal and to observed negative magnetization, at moderate applied fields, below T comp. Both vertical and horizontal shifts from the origin were gotten in the field-cooled magnetization hysteresis loops. The EB sign was found to be positive below T comp and negative above T comp , with nonmonotonic dependence on cooling field H cool. It sharply increases at small values of magnetic fields up to H cool ∼ 1 kOe, then remains almost unchanged in the range 1-30 kOe and strongly decreases with further increase of H cool. This unusual behavior results from the competition of various Dzyaloshinskii-Moriya interactions between Fe 3+ and Cr 3+ ions.

The possibility of inducing superconductivity in Weyl semimetal through coupling its surface to a superconductor was investigated. A single crystal of NbP, grown by chemical vapor transport method, was carefully characterized by XRD, EDX, SEM, ARPES techniques and by electron transport measurements. The mobility spectrum of the carriers was determined and it was found that there are four separate sharp peaks visible, which indicates that the carriers participating in the conductance have four different (almost discrete) mobilities. For the studies of interface transmission, the (001) surface of the crystal was covered by several hundred nm thick metallic layers of either Pb, or Nb, or In. DC current-voltage characteristics and AC differential conductance through the interfaces were investigated. The measurements were carried out as a function of temperature and the results were interpreted in terms of the modified Blonder-Tinkham-Klapwijk model. Upon cooling of the devices during which the metals become superconducting, qualitatively different behavior of each type of junctions was observed. The junctions with Nb and Pb show high interface transmission pointing out the Andreev reflection as a prevalent contribution to the subgap conductance. This also indicates that both Pb and Nb superconductors are promising candidates for further studies of the proximity-induced superconducting Weyl semimetals. However, in the case of In, an alloyed interface region is formed, which presumably excludes this metal from such studies.