Fast domain wall dynamics in MnAs films

M. TORTAROLO; L. THEVENARD; H. J. VON BARDELEBEN; M. CUBUKCU; V. H. ETGENS; M. EDDRIEF; C. GOURDON

Bariloche

Workshop; NANO 2017; 2017

INN-CAB

The possibility of storing information in magnetic domains separated by domain walls (DW) moving along domain tracks has stimulated a renewed interest in DW propagation in in-plane magnetized materials for spintronics[1]. Most studies are performed on Permalloy where high DW velocities (up to 1000 m s-1) can be achieved[2]. However it is well known that MnAs is a promising candidate for spintronics applications as it can be grown on different semiconductors[3]. Even though the domain wall (DW) dynamics in ferromagnetic films has been intensively studied during the last decades DW propagation in MnAs was studied only recently, and has been limited to the slow DW evolution (velocity  30 m s-1) under application of a magnetic field close to the coercive field[4]. Using longitudinal Kerr microscopy and a field pulse technique, we have investigated the DW dynamics in MnAs/GaAs over a wide range of magnetic field and temperature values, below and within the coexistence regime of the (ferromagnetic)  phase and (non-ferromagnetic)  phase[5]. The DW reversal in the studied temperature range shows wedge magnetic domains (Figure 1). The analysis of the velocity curves leads to the identification of different dynamical regimes given by the interplay of the depinning field Hdep and the Walker field HW. A maximum DW velocity of 940 m s-1 is measured at 200K. Remarkably it is still as high as 500 m s-1 at 290 K within the coexistence regime.