Robustness in Coupling Between Iron and Rare Earth Spins in Rare Earth Orthoferrites

We report on very accurate magnetic measurements on large rare earth orthoferrites single crystals of ErFeO3 and NdFeO3. Our results show that the interaction between rare earth and iron spin system does not change during the spin-flip process. This implies that the coupling between the iron and rare earth spin systems is robust enough to withstand the effects of spin flipping against the magnetic anisotropy energy. This is despite rare eath ions, polarized by the ordered iron ions, being in partly metastable state and their magnetic moment decays with time.