Electronic structure and magnetic properties of Mn1-xCrxSb alloys.

The electronic structure and magnetic properties of Mn1-xCrxSb alloys were investigated for the full concentration range. The stability of the concentration-dependent magnetic structure of the alloys were analysed on the basis of spin-spiral calculations as well as using the Monte Carlo (MC) simulations based on the Heisenberg model with the exchange coupling parameters calculated from first-principles. A leading contribution to the canted magnetic structure in Mn1-xCrxSb is the competition of the direct Cr-Cr and Mn-Mn exchange interactions having opposite signs. Furthermore, a strong impact of long-distance RKKY-type interactions is demonstrated. MC simulations at finite temperature were used to obtain the magnetic phase diagram for Mn1-xCrxSb alloys, which is in reasonable agreement with the experimental data.

Correlation effects in fcc-Fe(x)Ni(1-x) alloys investigated by means of the KKR-CPA.

The electronic structure and magnetic properties of the disordered alloy system fcc-FexNi1-x (fcc: face centered cubic) have been investigated by means of the KKR-CPA (Korringa-Kohn-Rostoker coherent potential approximation) band structure method. To investigate the impact of correlation effects, the calculations have been performed on the basis of the LSDA (local spin density approximation), the LSDA + U as well as the LSDA + DMFT (dynamical mean field theory). It turned out that the inclusion of correlation effects hardly changed the spin magnetic moments and the related hyperfine fields. The spin-orbit induced orbital magnetic moments and hyperfine fields, on the other hand, show a pronounced and element-specific enhancement. These findings are in full accordance with the results of a recent experimental study.

Magnetic behaviour of Er1-xZrxFe2 intermetallic compounds.

In this work, the structural and magnetic properties of Er1-xZrxFe2 (0.1 ≤ x ≤ 0.4) were investigated. These compounds crystallize in the cubic MgCu2 (C15) structure, the lattice parameters decreasing with Zr content. Electronic structure calculations were performed, showing a good agreement between theory and experiment. All of the samples are ferrimagnetically ordered, presenting compensation points in the M(T) plots. The compensation point values decrease, while the Curie temperatures increase with Zr content. The experimental Fe moments at 5 K decrease with Zr content from 1.70 µB/atom for x = 0.1 to 1.55 µB/atom for x = 0.4. A non-collinear orientation of the magnetic moments was evidenced in these compounds. The magnetocaloric effect was also studied. A modest magnetocaloric effect was found for all of the samples, spreading across a wide temperature range. A maximum |ΔSM| value of 1.19 J kg(-1) K(-1) was found for the sample with x = 0.1 for an applied field change of 0-4 T. Large RCP(ΔS) values were obtained for all of the samples, mainly due to the wide δTFWHM values of the ΔSM(T) curves.

Finite-temperature magnetism of CrTe and CrSe.

An investigation on the electronic and magnetic properties of NiAs-type CrTe and CrSe has been performed for ferromagnetic, antiferromagnetic and non-collinear spin configurations, using the spin-polarized relativistic KKR (Korringa-Kohn-Rostoker) band structure method. Calculated exchange coupling parameters, as well as the total energy calculated as a function of the tilt angle of magnetic moments, indicate the presence of a non-collinear spin structure in CrTe and CrSe. The existence of a non-collinear spin structure is also shown by Monte Carlo (MC) simulations used for studies on the temperature dependent magnetization. The results are compared with available results in the literature and are in satisfactory agreement with the experimental results.

Direct observation of the multisheet Fermi surface in the strongly correlated transition metal compound ZrZn2.

The existence of flat areas of a Fermi surface (FS), predicted by electronic structure calculations and used in models of both magnetically mediated and phonon-mediated Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, is reported in the paramagnetic phase of the ferromagnetic superconductor ZrZn2 using positron annihilation. The strongly mass-renormalized FS sheet, dominating the Fermi level density of states, is seen for the first time. The delocalization of the magnetization is studied using measured and calculated magnetic Compton profiles.

Layer-resolved magnetic moments in Ni/Pt multilayers

The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically "dead" Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.