Search

The (110) oriented Nb-Fe multilayers (MLs) with constant Fe and variable Nb sublayer thicknesses were prepared at room temperature using UHV magnetron sputtering. The artificial periodicity was revealed by intense satellite peaks in the low- and high-angle X-ray diffraction patterns. Magnetic hysteresis loop measurements at 5 K revealed antiferromagnetic (AF) exchange coupling of the Fe sublayers for Nb spacer thickness of about 3 monolayers. The corresponding AF coupling energy is equal to about -1.36 mJ/m². The Nb spacer thickness corresponding to the position of the AF peak is in good agreement with ab-initio calculations within localized spin density approximations of exchange-correlation potential. [ABSTRACT FROM AUTHOR]

Fe/Nb/Fe trilayers were prepared at room temperature using UHV magnetron sputtering. The interlayer exchange coupling energy was determined from a shift of the minor hysteresis loop from the origin. Results showed clear antiferromagnetic (AF) coupling maxima near ~ 6 and 9 monolayers of Nb spacer. Calculations of the interlayer exchange coupling energy were carried out using ab-initio method with localized spin density approximations of exchange-correlation potential. The experimental results were in good agreement with ab-initio calculations. Furthermore, the position of the AF peaks and coupling energy values could be modified using hydrogen. [ABSTRACT FROM AUTHOR]

We have studied interlayer exchange coupling (IEC) in (110) oriented V/Fe multilayers with ultrathin sublayers up to 7 monolayers (ML). Results showed that IEC energy depends on both vanadium and iron layer thicknesses. The local maxima of the antiferromagnetic coupling were found for V(7 ML)/Fe(4 ML) and V(3 ML)/Fe(3 ML) multilayers (MLs). The strongest AFM coupling energy of about 1.0 mJ/m² was measured at 5 K for the V(7 ML)/Fe(4 ML) multilayer. The position of the AFM peak for V(X ML)/Fe(3 ML) MLs near 3 ML of V spacer was also revealed by ab-initio calculations. Furthermore, theoretical calculations show an induced negative magnetic moment on V atoms near the V-Fe and Fe-V interfaces due to the proximity effect. [ABSTRACT FROM AUTHOR]

Ab initio calculations shown that the Co substitution instead of Ni in Ni2MnGe with the L21 crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni2-xCoxMnGe compounds. The Mn(B) has the largest local moment above 3 μB coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of 0:19 ÷ 0:26 μB for Ni(A,C) and 1:03 ÷ 0:97 μB for Co(A,C) for studied range of x. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS. [ABSTRACT FROM AUTHOR]

The aim of presented first principles study of La0:5Bi0:5NiO3 is to investigate electronic structure of orthorhombic phase Pbnm. The calculations show that metallicity and magnetism of the system are strongly related with hybridization between Ni 3d and O 2p. To improve the quality of the electronic structure description of the system, especially the treatment of correlation for the Ni 3d, we employ GGA, LDA, and GGA+U, LDA+U. The LSDA results give good agreement with experiment. Thus, the screening effects originating from the hybridized Ni 3d and O 2p electrons are sufficiently strong that they reduce the electronic correlations in the La0:5Bi0:5NiO3, making it a weakly correlated metal. [ABSTRACT FROM AUTHOR]

We present results of first-principles calculations for Bi5GdFe6O18 compound in idealized the rhombohedral R3c structure for a variety of magnetic ordering. Within DFT+U approach it is found that the insulating ground state with the G-type antiferromagnetic arrangement of ft sublattice gives a minimal total energy for BiFeO3 substituted by magnetically active Gd3+. The Bi5GdFe6O18 compound has nonzero total magnetic moment, which arises from antiparallel spin moments on Fe sites and reduced spin moment on Gd. Chemical bonding of the studied compound is analyzed using partial density of states, electron localization function and charge density distribution. [ABSTRACT FROM AUTHOR]

The electronic structure of different phases of BiFeCO3 were calculated by using density functional theory. The DFT+U and semilocal Tran-Blaha modified Becke-Johnson potential were used. DFT+U results are in good agreement with previous calculations. Our results have shown that in case of R3c, Pnma, Pn21a BiFeCO3 has G-antiferromagnetic ordering and C-antiferromagnetic in case of Cm space group. In ali calculated structures BiFeCO3 is a semiconductor with the band gap: 2.26 eV (2.27 eV) for R3c, 1.91 eV (1.66 eV) for Pnma, 1.99 eV (2.18 eV) for Pn21a and 2.09 eV (2.55 eV) for Cm within DFT+U (Tran-Blaha modified Becke-Johnson). [ABSTRACT FROM AUTHOR]

We present results of first-principles calculations for Bi5GdFe6O18 compound in idealized the rhombohedral R3c structure for a variety of magnetic ordering. Within DFT+U approach it is found that the insulating ground state with the G-type antiferromagnetic arrangement of ft sublattice gives a minimal total energy for BiFeO3 substituted by magnetically active Gd3+. The Bi5GdFe6O18 compound has nonzero total magnetic moment, which arises from antiparallel spin moments on Fe sites and reduced spin moment on Gd. Chemical bonding of the studied compound is analyzed using partial density of states, electron localization function and charge density distribution. [ABSTRACT FROM AUTHOR]