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Ni–Fe asymmetric ring dots with partially planed outer sides were investigated as candidates for high-density magnetic memory cells. The magnetic states, which were measured with magnetic force microscopy, show that in-plane magnetic fields can control the chirality, either clockwise or counterclockwise, of vortical magnetizations of the Ni–Fe asymmetric ring dots. This control facilitates applying ring dots to the magnetic random access memories. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The read-cycle endurance of a magnetic tunneling junction (MTJ) has been investigated, focusing on the spin-dependent tunneling current at high temperatures. The MTJ structure used in this study consisted of Ta-NiFe-CoFe-AlOx-CoFe-IrMn-NiFe-Ta prepared on a thermally oxidized Si wafer. Both the tunneling current and tunneling magnetoresistance ratio showed no significant degradation during the 1E9 read-cycle test using unipolar voltage pulses of 0.5 V at room temperature. Temperature dependence of the MTJs resistance calculated from the measured tunneling current has also been examined in a temperature range from room temperature to 175 °C. Furthermore in the case of read-cycle tests for thermally stressed MTJs, the variation of the tunneling current was less than 2% after 1E9 cycles at a stress temperature of 175 °C. This indicates that MTJs have sufficient read-cycle endurance under high-temperature operation. [ABSTRACT FROM AUTHOR]

Abstract: Ni–Fe/Mn–Ir asymmetric ring dots with partially planed outer sides are investigated in order to confirm a method for obtaining pinned layers in magnetic memories with asymmetric ring shapes. Magnetic force microscopy revealed that the direction of vortical magnetization is pinned in Ni–Fe/Mn–Ir asymmetric ring dots despite the direction of the magnetic fields. This investigation shows that the Ni–Fe/Mn–Ir asymmetric ring dots can be applied to pinned layers in magnetic memories with asymmetric ring shapes. [Copyright &y& Elsevier]