Magneto-Elastic Coupling in RbMnF3

Abstract

Magneto-elastic (ME) coupling effects in the simple cubic antiferromagnet RbMn${\mathrm{F}}_3$ have been studied by observing shifts in antiferromagnetic resonance (AFMR) frequency and changes in AFMR line shape with the application of axial stress. Antiferromagnetic resonance in a two-sublattice antiferromagnet with a general anisotropy and ME interaction is analyzed. Formulas for the evaluation of ME constants of a two-sublattice cubic antiferromagnet are presented. ME constants of RbMn${\mathrm{F}}_3$ have been determined as a function of temperature from measurements of AFMR in single-crystal specimens under applied stress. The spin-lattice strain coefficients in the spin Hamiltonian for $S$-state ${\mathrm{Mn}}^{2+}$ in RbMn${\mathrm{F}}_3$ have been determined from experimental ME constants and calculated magnetic dipolar ME constants. Large changes in the static and dynamic response of low-anisotropy RbMn${\mathrm{F}}_3$ can be effected by the application of stress; via ME coupling, applied stress can change both the form and magnitude of the total anisotropy. The measured AFMR linewidth of RbMn${\mathrm{F}}_3$ at low temperatures is shown to be due to inhomogeneous strain broadening. The intrinsic relaxation linewidth is estimated to be less than 5 Oe.