Reference lattice, sound, stiffness, and magnetic transitions of Ising monolayers

TL;DR

This paper introduces a reference lattice model for 2D magnets, analyzing elastic distortions, sound anisotropy, and magnetic phase transitions in Ising monolayers, exemplified by CrSiTe3.

Contribution

It proposes a novel reference lattice approach based on atomic positions of FM and AFM states to understand magneto-elastic effects in 2D magnets.

Findings

Elastic stiffness constants are reported.

Anisotropic vibrational frequencies are explained.

Strain thresholds for magnetic phase transitions are determined.

Abstract

A reference lattice, away from which elastic distortions induced by the spin texturing of 2D magnets take hold, is motivated from a picture of pairwise Biot-Savart interactions among identical solenoids that either elongate or compress a (``zero-current'') spring lattice. Applied to a paradigmatic CrSiTe$_3$ monolayer (ML), the reference is given by the average between the atomic positions of FM and N\'eel AFM lattices; such an atomic disposition permits understanding structural distortions and elastic energies due to magnetism readily. Furthermore, the anisotropic speed of sound in the magnetic ground state explains an observed anisotropy of vibrational frequencies on similar magnets. Elastic stiffness constants are reported, too. Magnetic energies in four Ising structural configurations were calculated, and the strain needed for those 2D magnets to undergo an AFM to FM quantum phase transition was determined as well.