Depth-dependent magnetism in epitaxial MnSb thin films: effects of surface passivation and cleaning.

Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide ∼4.5 nm thick covers air-exposed samples which increases the film's coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L(3,2) edge XMCD data is discussed.

Room-temperature ferromagnetism of Cu-doped ZnO films probed by soft X-ray magnetic circular dichroism.

We report direct evidence of room-temperature ferromagnetic ordering in O-deficient ZnO:Cu films by using soft x-ray magnetic circular dichroism and x-ray absorption. Our measurements have revealed unambiguously two distinct features of Cu atoms associated with (i) magnetically ordered Cu ions present only in the oxygen-deficient samples and (ii) magnetically disordered regular Cu2+ ions present in all the samples. We find that a sufficient amount of both oxygen vacancies (V(O)) and Cu impurities is essential to the observed ferromagnetism, and a non-negligible portion of Cu impurities is uninvolved in the magnetic order. Based on first-principles calculations, we propose a microscopic "indirect double-exchange" model, in which alignments of localized large moments of Cu in the vicinity of the V(O) are mediated by the large-sized vacancy orbitals.

Reconstruction of magnetization density in two-dimensional samples from soft X-ray speckle patterns using the multiple-wavelength anomalous diffraction method.

A non-destructive technique for imaging magnetic domains in thin films and two-dimensional magnetic structures using coherent soft X-ray scattering and the multiple-wavelength anomalous diffraction method (MAD) is proposed. The method exploits the strong energy dependence in the magnetic scattering amplitude for 3d transition metals near the L(2,3) absorption edges and 4f elements near the M(4,5) absorption edges. The phase information required in the reconstruction algorithm is derived from the interference between the charge and magnetic scattering amplitudes. Magnetic speckle patterns from the magnetic domain distribution in an artificially defined Fe thin film are used to demonstrate this reconstruction algorithm. Circularly and linearly polarized incident light are examined separately to investigate the effect of polarization on the capability of the method.