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

Abstract

We report on the determination of micromagnetic parameters of epilayers of the ferromagnetic semiconductor (Ga,Mn)As, which has an easy axis in the sample plane, and (Ga,Mn)(As,P), which has an easy axis perpendicular to the sample plane. We use an optical analog of ferromagnetic resonance where the laser-pulse-induced precession of magnetization is measured directly in the time domain. By the analysis of a single set of pump-and-probe magneto-optical data, we determined the magnetic anisotropy fields, the spin stiffness, and the Gilbert damping constant in these two materials. We show that incorporation of 10% of phosphorus in (Ga,Mn)As with 6% of manganese leads not only to the expected sign change of the perpendicular-to-plane anisotropy field but also to an increase of the Gilbert damping and to a reduction of the spin stiffness. The observed changes in the micromagnetic parameters upon incorporating P in (Ga,Mn)As are consistent with the reduced hole density, conductivity, and Curie temperature of the (Ga,Mn)(As,P) material. We also show that the apparent magnetization precession damping is stronger for the n = 1 spin wave resonance mode than for the n = 0 uniform magnetization precession mode.

Systematic study of the spin stiffness dependence on phosphorus alloying in the ferromagnetic semiconductor (Ga,Mn)As

“…3), and for the third one (on a GaInAs buffer, with perpendicular easy axis) from the width of individual stripe domains close to saturation 14 are all very close: 4.75 6 0.5, 4.8 6 0.5, and 5.2 6 0.7 T nm 2 , respectively, which again is in favor of an even second PSSW mode in TRMOKE. Let us note that the spin stiffness values for GaMnAs reported in the literature are quite dispersed, some being comparable to ours, 17,18 others, especially for thicker but likely inhomogeneous samples, being at least 3 times larger, 4,18 or 4 times larger by TRMOKE but under the assumption of a second odd mode, 16 which would give a value close to ours assuming an even second mode.…”

“…14,15 However, recent results using an optical technique suggest a decrease of D with P alloying but with only one (Ga,Mn)(As,P) sample studied. 16 Unfortunately domain pattern analysis cannot be used to determine the spin stiffness for in-plane (IP) magnetized samples. To assess this value at low P concentration and in-plane easy axis, techniques based on the excitation of exchange related perpendicular standing spin waves (PSSW) can instead be used.…”

“…The spin stiffness constant can be extracted from the frequency spacing of excited modes. One technique is the standard ferromagnetic resonance (FMR), 4,17 another is the time-resolved magnetooptical Kerr effect experiment (TRMOKE) 6,16,18,19 recently pointed out as an optical analog of FMR for DMS. 19 However, experimentally some modes undetectable by FMR are observed by TRMOKE as will be shown further on.…”

Extreme asymmetry of Néel domain walls in multilayered films of the dilute magnetic semiconductor (Ga,Mn)(As,P)

“…Above analysis accounts for the isotropic exchange stiffness, A, as commonly assumed in micromagnetic treatment of (Ga,Mn)As [34][35][36]. However, many first principle calculations show that the exchange constants in zinc-blende DMS structure may be anisotropic, which holds when neglecting spin-orbit coupling (SOC) [36][37][38], and is even more robust if SOC is taken into account [20,38,40,41,6].…”

Damping of Standing Spin Waves in Bismuth-Substituted Yttrium Iron Garnet as Seen via the Time-Resolved Magneto-Optical Kerr Effect

“…Traditionally, the investigation of SWs and their damping are performed using ferromagnetic resonance (FMR) techniques [6,7]. Alternatively, femtosecond laser pulses have been recently presented as an important tool to trigger SWs in a wide variety of conducting [8][9][10], semiconducting [11][12][13][14][15], and insulating [16][17][18][19][20][21] magnetic materials, as well as probing their real-time dynamics with a very high spatiotemporal resolution using femtosecond magneto-optical pump-probe techniques [22][23][24][25][26]. These highly resolved spatiotemporal investigations provide important opportunities to improve the understanding of SWs, with the aim * madeb@uni-potsdam.de of manipulating their dynamics at the fastest speed and in the most efficient way.…”