Direct measurement of the three-dimensional magnetization vector trajectory in GaMnAs by a magneto-optical pump-and-probe method

Abstract

We report on a quantitative experimental determination of the three-dimensional magnetization vector trajectory in GaMnAs by means of the static and time-resolved pumpand-probe magneto-optical measurements. The experiments are performed in a normal incidence geometry and the time evolution of the magnetization vector is obtained without any numerical modeling of magnetization dynamics. Our experimental method utilizes different polarization dependences of the polar Kerr effect and magnetic linear dichroism to disentangle the pump-induced out-of-plane and in-plane motions of magnetization, respectively. We demonstrate that the method is sensitive enough to allow for the determination of small angle excitations of the magnetization in GaMnAs. The method is readily applicable to other magnetic materials with sufficiently strong circular and linear magneto-optical effects.

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

“…Hand-in-hand with the optimization of the material synthesis, we have developed experimental capabilities based on the MO pump-and-probe method that allows us to simultaneously determine the magnetic anisotropy, Gilbert damping and spin stiffness constants from one consistent set of measured data. The possibility to excite and detect precession of ferromagnetic Mn moments in (Ga,Mn)As by this method has been extensively discussed in previous MO studies (see Methods and Supplementary Notes 6-9 for the detailed description of the method) [30][31][32][33][34][35][36][37][38][39][40][41] . All experiments presented below were performed at 15 K. The anisotropy constants, shown in Fig.…”

“…To uniquely determine the anisotropy constants, the field-dependent precession frequency measurements were complemented by MO experiments with variable polarization angle of the probe beam. The latter measurements allow us to precisely determine the angle of the equilibrium easy axis of the magnetization (Supplementary Note 7) 40,41 . Finally, we confirmed the consistency of the obtained anisotropy constants by performing static measurements of magnetization hysteresis loops by the superconducting quantum interference device.…”

Comparison of micromagnetic parameters of the ferromagnetic semiconductors (Ga,Mn)(As,P) and (Ga,Mn)As

“…The rotation of the probe polarization plane is caused by two MO effects-the polar Kerr effect and the magnetic linear dichroism, which are sensitive to perpendicular-to-plane and in-plane components of magnetization, respectively [31][32][33]. For all MO experiments, samples were mounted in a cryostat and cooled down to ≈15 K. The cryostat was placed between the poles of an electromagnet, and the external magnetic field H ext ranging from ≈0 to 585 mT was applied in the sample plane, either in the [010] or [110] crystallographic direction of the sample (see inset in Fig.…”

Manipulation of ferromagnets via the spin-selective optical Stark effect

“…22 Although their Curie temperature at present is below room temperature, studying these materials can improve our understanding of novel physical phenomena that are also present in other magnets. [23][24][25] Photoinjected carriers induced by linearly polarized light with frequency slightly above the or L band edges have been shown to induce magnetization dynamics in GaMnAs. 23,26 In contrast, we focus here on excitation with frequencies below the fundamental band gap, which is dissipationless, since no free carriers are excited.…”