We obtained the spin-wave spectrum based on a first-principles method of exchange constants, calculated the phonon spectrum by the first-principles phonon calculation method, and extracted the broadening of the magnon spectrum, ∆ω, induced by magnon-phonon interactions in gadolinium iron garnet (GdIG). Using the obtained exchange constants, we reproduce the experimental Curie temperature and the compensation temperature from spin models using Metropolis Monte Carlo (MC) simulations. In the lower-frequency regime, the fitted positions of the magnon-phonon dispersion crossing points are consistent with the inelastic neutron scattering experiment. We found that the ∆ω and magnon wave vector k have a similar relationship in YIG. The broadening of the acoustic spin-wave branch is proportional to k 2 , while that of the YIG-like acoustic branch and the optical branch are a constant. At a specific k, the magnon-phonon thermalization time of τmp are approximately 10 −9 s, 10 −13 s, and 10 −14 s for acoustic branch, YIG-like acoustic branch, and optical branch, respectively. This research provides specific and effective information for developing a clear understanding of the spin-wave mediated spin Seebeck effect and complements the lack of lattice dynamics calculations of GdIG. arXiv:1912.10432v1 [cond-mat.mtrl-sci] 22 Dec 2019 Gd Fe T O J dc J ac J aa J dd J ad J aa J dd J ad J ac J dc J

We design and fabricate a good performance silicon photoconductive terahertz detector on sapphire substrates at room temperature. The best voltage responsivity of the detector is 6679V/W at frequency 300 GHz as well as low voltage noise of 3.8 nV/Hz1/2 for noise equivalent power 0.57 pW/Hz1/2. The measured response time of the device is about 9 μ s , demonstrating that the detector has a speed of > 110 kHz . The achieved good performance, together with large detector size (acceptance area is 3 μ m × 160 μ m ), simple structure, easy manufacturing method, compatibility with mature silicon technology, and suitability for large-scale fabrication of imaging arrays provide a promising approach to the development of sensitive terahertz room-temperature detectors.