  Terahertz spin waves could be generated on-demand via all-optical
manipulation of magnetization by femtosecond laser pulse. Here, we present an
energy balance model, which explains the energy transfer rates from laser pulse
to electron bath coupled with phonon, spin, and magnetization of five different
magnetic metallic thin films: Iron, Cobalt, Nickel, Gadolinium and Ni$_{2}$MnSn
Heusler alloy. Two types of transient magnetization dynamics emerge in metallic
magnetic thin films based on their Curie temperatures (T$_{C}$): type I (Fe,
Co, and Ni with T$_{C}$ > room temperature, RT) and type II films (Gd and
Ni$_{2}$MnSn with T$_{C}$ $\approx$ RT). We study the effect of laser fluence
and pulse width for single Gaussian laser pulses and the effect of metal film
thickness on magnetization dynamics. Spectral dynamics show that broadband spin
waves up to 24 THz could be generated by all-optical manipulation of
magnetization in these nanofilms.
