Phonon, electron, and magnon excitations in antiferromagnetic L10 -type MnPt

Antiferromagnetic $L{1}_{0}$-type MnPt is a material with relatively simple crystal and magnetic structures, recently attracting interest due to its high N\'eel temperature and wide usage as a pinning layer in magnetic devices. While it is experimentally well characterized, the theoretical understanding is much less developed, in part due to the challenging accuracy requirements dictated by the small underlying energy scales that govern magnetic ordering in antiferromagnetic metals. In this paper, we use density functional theory, the Korringa-Kohn-Rostoker formalism, and a Heisenberg model to establish a comprehensive theoretical description of antiferromagnetic $L{1}_{0}$-type MnPt, along with accuracy limits, by thoroughly comparing to available literature data. Our simulations show that the contribution of the magnetic dipole interaction to the magnetocrystalline anisotropy energy of ${K}_{1}=1.07\ifmmode\times\else\texttimes\fi{}{10}^{6}$ J/m${}^{3}$ is comparable in magnitude to the spin-orbit contribution. Using our result for the magnetic susceptibility of $5.25\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, a lowest magnon frequency of about 2.02 THz is predicted, confirming THz spin dynamics in this material. From our data for electron, phonon, and magnon dispersion, we compute the individual contributions to the total heat capacity and show that the dominant term at or above 2 K arises from phonons. From the Landau-Lifshitz-Gilbert equation, we compute a N\'eel temperature of 990--1070 K. Finally, we quantify the magnitude of the magneto-optical Kerr effect generated by applying an external magnetic field. Our results provide insight into the underlying physics, which is critical for a deep understanding of fundamental limits of the time scale of spin dynamics, stability of the magnetic ordering, and the possibility of magneto-optical detection of collective spin motion.