Magnetic anisotropy manipulation of the femtosecond laser-excited spin wave modes in full-Heusler Co₂Fe_1−x Mn _x Al films

Abstract

Spin-wave dynamics in full-Heusler Co 2 Fe 1−x Mn x Al films have been investigated using alloptical pump-probe magneto-optical polar Kerr spectroscopy. We find magnetic damping and anisotropy can be modulated by composition x. Damon-Eshbach (DE) spin wave occurs only in the samples which present intrinsic magnetic damping and have huge uniaxial magnetic anisotropy, implying that intrinsic magnetic damping and huge uniaxial magnetic anisotropy is the necessary conditions to excite coherent DE spin wave. Kittel spin wave appears in low uniaxial magnetic anisotropic samples and presents extrinsic magnetic damping. Therefore, laser-excited spin-wave modes can be manipulated by magnetic anisotropy, whose physical picture is discussed phenomenologically.

The unique magnetic damping enhancement in epitaxial Co2Fe1−xMnxAl films*

“…In contrast, it is consistent with the increased magnetic damping observed in Fe 3 O 4 films due to the enhancement of homogenous magnetization. [23] As reported, the homogeneous magnetization facilitates the excitation of spin wave mode, [27] and then the uniform precession mode can transfer its energy to the spin wave mode. [23] In the low-field regime, the inhomogeneity dominated by the competition between H 2 and H 4 hinders the energy transfer from uniform precession mode to spin wave mode, leading to the small magnetic damping.…”

“…[20] In contrast, the decay time observed in many Heusler alloys normally increases with external magnetic field. [14,15,27] More interestingly, the extracted decay time reduces rapidly at low magnetic field comparing with the slight drop at high magnetic field. In addition, it increases as x increases, indicating the slow decay of uniform precession mode in Mn-rich sample.…”

“…The frequency of this PSSW mode is huge, on the order of 250 GHz, due to the inverse relationship of square of the thickness. [16,27] It is difficult to detect this huge-frequency PSSW mode in our experiment because of the very small period and very fast decay. Therefore, in future, more experiments are needed to study the characteristics of this increased magnetic damping in uniform precession mode, and then to deeply understand the behind mechanism.…”

Excitation fluence dependence of spin-wave dynamics and intrinsic Gilbert damping in epitaxial Co2FeAl film

“…2,7,8) Therefore, it is greatly interesting to study the spin-wave dynamics and understand the mechanism of Gilbert damping in Heusler alloy films. However, the value of Gilbert damping observed in Heulser alloy films has a large scattering, 1,6,[9][10][11][12][13][14] and the behind mechanism is still unclear. The intrinsic Gilbert damping obtained in Co 2 FeAl films only as change of temperature was found to increase with decreasing temperature, 15) which may be attributed to the reduction of electron-phonon scattering rate.…”