Spin-Orbit Torque Driven Magnetization Dynamics in (Ga,Mn)As and (Ga,Mn)(As,P) Dilute Magnetic Semiconductors
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Spintronics-based technologies are poised to leapfrog the current limitations on the scaling, speed, and power consumption of electronic devices. Conventional devices rely on complex structures and magnetic-field-based switching to manipulate data. In order to overcome these limits, new methods must be developed to reliably transmit and store data more efficiently. The understanding and manipulation of magnetic domain walls (DWs) may play a pivotal role in the development of new non-volatile and down-scalable logic and memory devices. This thesis investigates current-induced magnetization dynamics and control mechanisms in the ideal ferromagnetic semiconductors Phosphorus-doped Gallium Manganese Arsenide (Ga,Mn)(As,P) and Gallium Manganese Arsenide (Ga,Mn)As. In spin-orbit (SO) coupled materials with broken inversion symmetry, unpolarized electric fields provide a means to control magnetization orientation via the inverse spin-galvanic effect (ISGE). The ISGE generates a non-equilibrium spin-accumulation which can exert a torque on a magnetization if the spins are generated in (or injected into) a ferromagnetic material. This so-called current-induced spin-orbit torque (SOT) is calculated for a broad range of experimental parameters and compared with previous measurements. The study also assess the viability of using SOTs to control DW motion in semiconductor micro-structures. Typically, DW mobility is divided into steady and precession motion regimes with different mobilities, separated by the so-called Walker breakdown (WB). By manipulating the magnetic anisotropy of (Ga,Mn)(As,P) using piezoelectric strain, these experiments investigate the potential of strain to shift the WB, establishing strain-modified DW mobility as tool for electrically controlled DW motion.
Spin Orbit Couping
Domain Wall Motion
Vehstedt, Erin Kathleen (2014). Spin-Orbit Torque Driven Magnetization Dynamics in (Ga,Mn)As and (Ga,Mn)(As,P) Dilute Magnetic Semiconductors. Master's thesis, Texas A & M University. Available electronically from