First Principles Calculations of Fe on GaAs (100)

We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We find the Fe magnetic moment to be determined by the Fe-As distance. As segregates to the top of the Fe film, whereas Ga most likely is found within the Fe film. Moreover, we find an asymmetric in-plane contraction of our unit-cell along with an expansion perpendicular to the surface. We predict the number of Fe 3d-holes to increase with increasing Fe thickness on $p$-doped GaAs.Comment: 9 pages, 14 figures, submitted to PR

Unusual evolution of the magnetism on oxygen in La1-?Sr?CoO3

We present X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) data of La1-χSrχCoO3, for χ= 0.10-0.30, at the O K edge and then compare the results to local density approximation (LDA) and generalized gradient approximatio

Evolution of magnetic oxygen states in Sr-doped LaCoO 3

Magnetism in La 1-xSr xCoO 3 as a function of doping is investigated with x-ray absorption spectroscopy and x-ray magnetic circular dicrhoism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above E F and grow with increasing Sr doping. Density functional calculations for x=0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t 2g character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors

Exchange bias in a columnar nanocrystalline Ni80Fe20/CoO thin film

The effects of interfacial coupling at the boundary of ferromagnetic and antiferromagnetic components in a nanoscale columnar-structured thin film of Ni80Fe20/CoO have been examined. Field-cooling the film results in very different temperature dependences of the enhanced coercivity and exchange-bias shift of the hysteresis loop. The exchange-bias temperature dependence is well described by thermal fluctuations of the interfacial spins while the coercivity temperature dependence indicates that single-domain-like columns are being coherently rotated by the thermal fluctuations of the interface spins. Furthermore, only a portion of the spins in the antiferromagnetic layer seem to be associated with the spin coupling that results in exchange bias. X-ray magnetic resonant scattering measurements show clearly the presence of canted Co interfacial moments that provide a local field which enables exchange bias at a significantly higher temperature than the onset of an enhanced coercivity

Antiferromagnetic order in Co doped Fe5GeTe2 probed by resonant magnetic x ray scattering

The quasi two dimensional van der Waals magnet Fe5 amp; 8722; amp; 948;GeTe2 has emerged as a promising platform for electronic and spintronic functionalities at room temperature, owing to its large ferromagnetic ordering temperature TC amp; 8776; 315 K. Interestingly, by cobalt Co substitution of iron in F5GT, i.e., Fe1 amp; 8722;xCox 5 amp; 8722; amp; 948;GeTe2 Co F5GT , not only can its magnetic transition temperature be further enhanced, but the magnetic and structural ground states can also be tuned. Specifically, an antiferromagnetic AFM order is induced beyond the Co doping level x amp; 8805;0.4. Here, we investigate the magnetic properties of a Co F5GT single crystal at x 0.45 1 , by utilizing the element specific, resonant magnetic x ray scattering technique. Our study reveals an A type, Ising like AFM ground state, with a transition temperature TN amp; 8776; 340 K. In addition, our work unveils an important contribution from Co magnetic moments to the magnetic order. The application of the in plane magnetic fields gradually polarizes the spin moments along the field direction, but without inducing incommensurate spin texture