Pump-pulse induced magnetization reversal of amorphous Gd 23.1 Fe 71.9 Co 5.0 showed a subpicosecond magnetization collapse followed by a slower reversal. The reversal dynamics is well described by the Bloch equation via a reversal time that does not depend on temperature, but strongly decreases with increasing pump fluence. A comparison to data obtained in external saturation field and in remanence opened the way to separate the contributions due to temperature induced effects within single domains from those related to field induced domain formation.

Spintronics is a multidisciplinary field whose central theme is the active manipulation of spin degrees of freedom in solid-state systems. Ferromagnetic spintronics has been a main focus as it offers non-volatile memory and logic applications through current-induced spintransfer torques 1-4 . Enabling wider applications of such magnetic devices requires a lower switching current for a smaller cell while keeping the thermal stability of magnetic cells for non-volatility. As the cell size reduces, however, it becomes extremely difficult to meet this requirement with ferromagnets because spin-transfer torque for ferromagnets is a surface torque due to rapid spin dephasing 5,6 , leading to the 1/ferromagnet-thickness dependence of the spin-torque efficiency 7 . Requirement of a larger switching current for a thicker and thus

The motion of magnetic domain walls (DWs) in TbFeCo wires induced by low-current density up to 4:97 Â 10 10 A/m 2 has been directly observed by Kerr polarized optical microscopy. The critical current density slightly increases with wire width, from 4:97 Â 10 10 A/m 2 for 800-nm-width wires to 6:16 Â 10 10 A/m 2 for 1500-nm-width wires. DW velocity is estimated to be 28 AE 2 m/s, and mostly independent on the wire width. Increasing current density results in an increase of the wall velocity up to 59 AE 4 m/s. These findings indicate that TbFeCo nanowire is an excellent candidate for low-energy, fast accessing DW-controlled devices.

No abstract

Interfacial phase change memory (iPCM), that has a structure of a superlattice made of alternating atomically thin GeTe and Sb2Te3 layers, has recently attracted attention not only due to its superior performance compared to the alloy of the same average composition in terms of energy consumption but also due to its strong response to an external magnetic field (giant magnetoresistance) that has been speculated to arise from switching between topological insulator (RESET) and normal insulator (SET) phases. Here we report magneto-optical Kerr rotation loops in the visible range, that have mirror symmetric resonances with respect to the magnetic field polarity at temperatures above 380 K when the material is in the SET phase that has Kramers-pairs in spin-split bands. We further found that this threshold temperature may be controlled if the sample was cooled in a magnetic field. The observed results open new possibilities for use of iPCM beyond phase-change memory applications.