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CoCr films were deposited on three types of GaAs substrates, GaAs(001), GaAs(111), and Al oxide/GaAs(001). The perpendicular magnetic properties were investigated by magneto-optical Kerr-effect measurements. The direct deposition of the CoCr film on the GaAs substrate did not show any perpendicular magnetic properties. This fact indicates that the lattice distortion influenced by the GaAs lattice suppresses the perpendicular magnetism. The CoCr film on the Al oxide layer showed a tilted squarelike hysteresis loop. The thickness dependence of the hysteresis loop and the magnetic force microscopy showed that the onset thickness of ferromagnetism was 6.5 nm. The domain size of the CoCr films monotonously decreases with the increasing thickness (6.5–75 nm). [ABSTRACT FROM AUTHOR] more...

The magnetic structures of ferromagnetic-film-coated carbon nanotube (CNT) probes and conventional pyramidal probes for a magnetic force microscope (MFM) were simulated using three-dimensional micromagnetic simulation. The CNT-MFM probes with a total probe diameter less than 60 nm are almost uniformly magnetized along the longitudinal direction of the CNT, which is the ideal magnetic structure for MFM observations. On the other hand, the pyramidal probes had a vortex structure around the point tip, which suggests that they require a greater thickness of the ferromagnetic film because only part of the magnetic moment participates in the detection of the z-component of the stray field from samples. The advantages of the CNT-MFM probe are uniform magnetization along the longitudinal direction and magnetic imaging ability using a smaller coating thickness. [ABSTRACT FROM AUTHOR] more...

Abstract: We systematically investigated thickness and magnetization variations of the domain structures of MnAs films on GaAs(001) using magnetic force microscopy (MFM) at room temperature. The observed thickness range is from 5 to 500nm. The magnetic domain structures drastically change with increasing thickness because of the existence of the thickness-dependent periodic ridge-groove structure. The domain structures also depend on the magnetization histories. The MnAs films with the thickness of less than 50nm have no groove structure and the single magnetic domain is realized at the remanent state. In the thickness more than 100nm, on the other hand, the groove structures of paramagnetic β-MnAs appear. The complex magnetic domain structures of MnAs films result from the paramagnetic groove structures, the uniaxial anisotropy and weak perpendicular anisotropy. [Copyright &y& Elsevier] more...

The electronic structure of CrAs thin films with nominal thicknesses of 2 nm and 30 nm were studied by angle-resolved photoemission spectroscopy using synchrotron radiation. The CrAs film of 2 nm is expected to form a zinc-blende phase which is predicted to have a half-metallic band structure by theoretical calculation. On the other hand, it is considered that the CrAs film of 30 nm is a polycrystalline compound judging from reflection high-energy electron diffraction patterns. Different valence-band photoemission spectra were obtained for the two films. The photoemission spectra of the CrAs film of 30 nm showed no band dispersion, whereas a band dispersion was observed in that of the CrAs film with the nominal thickness of 2 nm. [ABSTRACT FROM AUTHOR] more...

Nanometer-scale structures were fabricated by anodic oxidation using scanning probe microscopes on thin-films of various 3d-metal compounds and alloys on GaAs, such as MnAs, MnSb, Cr2O3, CoCr and NiFe. Material variation advances the developments in nano-fabrication by scanning probe microscope. Comparing the oxidation conditions, new methodology for fabrication of nano-devices is explored. [Copyright &y& Elsevier] more...

Strong magnetic poles at characteristic rectangular defects have been observed using a magnetic force microscope on a MnAs(1¯ 1 0 0) thin film with the thickness of 30 nm. The MnAs thin film was epitaxially grown on a GaAs(0 0 1) substrate. The magnetic poles were in one-arranging direction, being independent of the magnetization direction of the film. The poles were pinned at the edges of the rectangular defects until just below the Curie temperature, and formed a stable magnetic-field loop on the MnAs surface. The stability of the magnetic pole pinning shows the distinctive feature of the magnetic domain structure on the surface with a strong anisotropy, which was built in the heterostructure of MnAs and GaAs. [Copyright &y& Elsevier] more...