Excitation of spin waves in ferromagnetic (Ga,Mn)As layers by picosecond strain pulses

Abstract

We demonstrate selective excitation of a spin wave mode in a ferromagnetic (Ga,Mn)As film by picosecond strain pulses. For a certain range of magnetic fields applied in the layer plane only a single frequency is detected for the magnetization precession. We explain this selectivity of spin mode excitation by the necessity of spatial matching of magnon and phonon eigenfunctions, which represents a selection rule analogous to momentum conservation for magnon-phonon interaction in bulk ferromagnetic materials.

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

“…2(c)) show that the first mode frequency does not change with decreasing thickness while the second one varies with the thickness as expected from Eqs. (5) and (6). This shows first that the sample magnetic properties have a good in-depth and lateral uniformity and, second, that we are observing two exchange related PSSWs, where the first mode is a quasi-uniform mode as found from the mode profile calculation (inset of Fig.…”

“…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.…”

“…1 is obtained in a y To extract D from the observed frequencies, the magnetization dynamics is modeled in a standard way, starting from the Landau-Lifshitz-Gilbert equation with the exchange field and without damping. 6,18 For in-plane easy-axis, the equations for small precession angle of the magnetization vector read…”

“…1 More fundamentally, DMS and more specifically the III-V based (Ga,Mn)As have become in the past decade a benchmark material in order to achieve predictable tuning of magnetic properties. Levers such as the temperature, 2 the carrier concentration 3,4 but also the strain applied on the magnetic layer 5,6 or alloying with phosphorus 7,8 have been used in order to change the micromagnetic properties, e.g., the Curie temperature T C , the saturation magnetization M s , and the magnetic easy axis.…”

Acoustic solitons: A robust tool to investigate the generation and detection of ultrafast acoustic waves

“…Solitons shorter than 200 fs with strain amplitude above 10 −3 have been inferred from experimental observations in MgO [3] and Al 2 O 3 [6] and could be useful to achieve carrier manipulation [9][10][11] or magnetic switching [12][13][14]. However, the absorbed optical power can raise the temperature of the sample so much that the attenuation is not negligible anymore.…”