Magnetocaloric effect: From materials research to refrigeration devices

A2B′B″O6 perovskites: A review

The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-007233.pdf

First-principles calculations of electronic structure and spectra of strongly correlated systems: the LDA+U method

Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as future energy applications and for spintronics. The semiconducting Heusler compounds can be identified by the number of valence electrons. The band gap can be tuned between 0 and 4 eV by the electronegativity difference of the constituents. Magnetism can be introduced in these compounds by using rare-earth elements, manganese or ‘electron’ doping. Thus, there is a great interest in the fields of thermoelectrics, solar cells and diluted magnetic semiconductors. The combination of different properties such as superconductivity and topological edge states leads to new multifunctional materials, which have the potential to revolutionize technological applications. Here, we review the structure, the origin of the band gap and the functionalities of semiconducting half-Heusler compounds.

https://iopscience.iop.org/article/10.1088/0268-1242/27/6/063001/pdf

Half-Heusler compounds: Novel materials for energy and spintronic applications

Geometrically frustrated magnets can host complex spin textures, leading to unconventional electromagnetic responses. Magnetic frustration may also promote topologically nontrivial spin states such as magnetic skyrmions. Experimentally, however, skyrmions have largely been observed in noncentrosymmetric lattice structures or interfacial symmetry-breaking heterostructures. Here, we report the emergence of a Bloch-type skyrmion state in the frustrated centrosymmetric triangular-lattice magnet Gd2PdSi3. We observed a giant topological Hall response, indicating a field-induced skyrmion phase, which is further corroborated by the observation of in-plane spin modulation probed by resonant x-ray scattering. Our results may lead to further discoveries of emergent electrodynamics in magnetically frustrated centrosymmetric materials.

Skyrmion lattice with a giant topological Hall effect in a frustrated triangular-lattice magnet

Magnetic properties of RERu2Si2 (RE=Pr, Nd, Gd, Tb, Dy, Er) interm etallics

Magnetic behaviour of R2PdSi3 compounds with R=Ce, Nd, Tb–Er

We have investigated the electronic structure and magnetic properties of the new ternary Ce 1 - x La x RhSn system. The 3d and 4d x-ray photoelectron spectroscopy (XPS) spectra indicate a mixed valence of Ce. Analysis of the 3d 9 4f 2 weight in the 3d XPS spectra using Gunnarsson-Schonhammer theory suggests a hybridization interaction A of about 120 meV for different compositions x of the system. The magnetic measurements indicate the existence of a highly anomalous weak ferromagnetic state below ∼220 K in Ce 1 - x La x RhSn for x 0.5 is dominated by spin fluctuations.

A. Zygmunt

Papers

Magnetic properties of RERu2Si2 (RE=Pr, Nd, Gd, Tb, Dy, Er) interm etallics

Magnetic behaviour of R2PdSi3 compounds with R=Ce, Nd, Tb–Er

Experimental study of the physical properties in the complex magnetic phase diagram of Ce 1-x La x RhSn

Neutron diffraction study of the crystal structure and magnetic properties of uranium ternary compounds UPt2Si2 and URh2Ge2

Neutron diffraction study of magnetic ordering in RAgSn (R = Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er) compounds