Magnetic structures and excitations of RCrO3 (R = Y and Rare earth metals)

This paper investigates the magnetic structures and excitations of the orthochromites $R$CrO$_3$. The neutron scattering intensities of these magnetic structures were calculated. For scenarios where the $R$ site is non-magnetic, the Bragg peaks (1 0 1) and (0 1 1) are good indicators to determine the magnetic structures. On the other hand, when the $R^{3+}$ sites are ordered magnetic ions, the Bragg peaks $I$(1 0 0) and $I$(0 1 0) become the indicators. This paper also discusses the magnetic excitations in $R$CrO$_3$, with a particular emphasis on the spin Hamiltonian related to the Cr$^{3+}$ ions. The calculations of spin-wave dispersion considering only exchange interactions indicate that the system lacks stability. Adding single-ion anistropy stabilizes the system while creating a gap at the $\Gamma$ point. The addition of the Dzyaloshinskii-Moriya interactions is necessary when the system has weak ferromagnetism, where this interaction not only widens the gap at the $\Gamma$ point but also creates the gap at the zone boundary, such as [1 0 2].