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Magnetization reversal phenomena in submicron half-ring patterned wires with different corner structures have been investigated. The wires with corner structures of rectangular, semicircle, and triangular shapes were connected in series by two or five half-rings. The variation of domain structures with magnetic field is illustrated by electron transport measurements, simulation, and magnetic force microscopy (MFM) images. The switching behavior depends on the corner structures connecting the half-ring structures. These results are consistent with the domain pattern and magnetic phase shift observation provided by the MFM measurements. [ABSTRACT FROM AUTHOR]

Domain wall pinning force in the junctions (corners), with different shapes of square, semicircle, or triangle, of half-ring in-series wires is considered to study the current injection induced wall movements. This geometry has less thermal activation at the region of domain wall nucleation in contrast to notch structures. The wires with square corners have the largest domain pinning force to resist polarized current-induced magnetization reversal, judging from the largest slope in the current-field dependence (ΔI/ΔH=0.274). [ABSTRACT FROM AUTHOR]

Temperature-dependent electron spin resonance (ESR) is applied to investigate La0.9Sr0.1MnO3 nanoparticles incorporating with magnetization and electrical transport measurements. Ferromagnetism is observed at room temperature which is much higher than the TC value for bulk samples ( $\sim $ 150 K). The ESR analysis confirms the coexistence of multiple magnetic phases consistent with the field-dependent magnetization-temperature curves. By fitting ESR spectra, the room-temperature multiphases are identified as the mixture of ferromagnetic and paramagnetic states, similar to the Griffiths phase observed in bulk samples. The field-dependent resistivity shows colossal magnetoresistance effect up to room temperature. Based on our analysis, the size-effect-induced room-temperature ferromagnetism is strongly correlated with the enhancement of the Griffith phase separation temperature. [ABSTRACT FROM AUTHOR]

The magnetization dynamics induced by a pulsed magnetic field is investigated by time- and polarization-resolved photoluminescene measurements in (Cd,Mn)Te/(Cd,Mg)Te quantum wells. The magnetization dynamics of Mn2+ ions is found to be strongly dependent on the external static magnetic field. A dynamical response of the magnetization on a subnanosecond time scale is observed at zero static magnetic field, while it drastically slows down and approaches the spin-lattice relaxation time constant for a nonzero static field. Theoretical calculations emphasize the importance of local spin interactions that interplay with the Zeeman interaction for the observed magnetization dynamics. [ABSTRACT FROM AUTHOR]

We studied nanoscale elliptical ring shaped NiFe/Cu/NiFe trilayer pseudo-spin-valve structures. The magnetization reversal processes showed simultaneous-reversal single-step transition or double-step transition involving flux closure states. For various aspect ratios (short axis to long axis) and linewidths, transition between single-step and double-step magnetization reversals was measured to form a phase diagram. When the linewidth was reduced, edge roughness became important. Simulations of the magnetization reversal behavior agreed qualitatively with our results. [ABSTRACT FROM AUTHOR]

We demonstrate a method to electrically manipulate the spin polarization in a semiconductor on a micrometer length scale and a submicrosecond time scale. A variable magnetic field induced by a microscale current loop magnetizes the Mn2+ ions in a CdMnTe/CdMgTe diluted magnetic semiconductor quantum well, and via sp-d exchange interaction polarizes photogenerated electron-hole pairs. A maximum spin polarization degree of ±8.5% is obtained at 4.2 K without external magnetic field. The induced carrier spin polarization and the thermal heating of Mn2+ spins are resolved spatially and temporally by microphotoluminescence measurements. [ABSTRACT FROM AUTHOR]