The authors investigate the insulator-layer-thickness-dependent temperature increment in the nanowire for the current-induced domain wall motion. Practically, a finite thickness insulator layer must be placed between the semi-infinite substrate and the metallic nanowire for an electric insulation. Since a good electric insulator is also a thermal insulator, the temperature increment of the nanowire depends on the insulator layer’s thickness. An approximated analytic expression of the insulator thickness dependent temperature increment is obtained by employing the Fourier-transformed Green’s function method, and it is confirmed by the full numerical finite element method. The authors find that the control parameter of the temperature increment is the ratio between the insulator layer’s thickness and the nanowire’s width.

We investigate voltage induced perpendicular magnetic anisotropy (PMA) changes in MgO/Cr/Au/Fe80Co20/MgO/polyimide/ indium tin oxide (ITO). In order to observe the PMA change, spin wave frequency was measured by Brillouin light scattering with finite bias voltages applied between Au and ITO electrodes. The obtained PMA constants from spin wave frequency of Fe80Co20 layer show clear bias voltage dependences, which agree well with the previous polar-Kerr effect measurement results and theoretical study. This study suggests spintronics devices operated by an electric field for next generation devices complying with low-power consumption.

The magnetic response of the mixture of 1-butyl-3-methylimidazolium tetrachloroferrate ͓͑bmim͔FeCl 4 ͒ and water was investigated. The ͓bmim͔FeCl 4 rich phase in the mixture forming two phases was easily separated under an external magnetic field. The homogeneous mixtures of ͓bmim͔FeCl 4 and water were also attracted to the direction of the magnetic field. Under a gradually varied magnetic field, the concentration of the mixture varied as a function of the magnetic field strength. We confirmed the possibility of a magnetic recovery system using the mixtures of ͓bmim͔FeCl 4 and water.

We report on the realization of voltage control of in-plane magnetic anisotropy at room temperature in ultrathin Fe∕n-GaAs(001) Schottky junctions. Clear voltage-induced changes in magnetic anisotropy were observed in a Kerr ellipticity hysteresis loop using a lock-in modulation technique. The maximum change reached 4.5% of the saturation ellipticity under the application of a sinusoidal voltage signal of 1V peak-to-peak in an Fe layer with a thickness of 0.64nm. These results reveal the feasibility of controlling the in-plane magnetization process by the use of a perpendicular electric field. This can be a useful technique in ultralow power magnetization switching.

PACs: 85.75.Àd 72.25.Ba 72.25.Pn 72.15.Eb Keywords: Current induced magnetization switching Spin transfer torque MRAM Nanopillar a b s t r a c tThe temperature increment due to the Joule heating in a nanopillar spin transfer torque system is investigated. We obtain a time-dependent analytic solution of the heat conduction equation in nanopillar geometry by using the Green's function method after some simplifications of the problem. While Holm's equation is applicable only to steady states in metallic systems, our solution describes the time dependence and is also applicable to a nanopillar-shaped magnetic tunneling junction with an insulator barrier layer. The validity of the analytic solution is confirmed by numerical finite element method simulations and by the comparison with Holm's equation.