Tuning the magnetocrystalline anisotropy in RCoPO by means of R substitution: A ferromagnetic resonance study

We report on broad-band electron-spin resonance measurements performed within the itinerant ferromagnetic phase of RCoPO (R = La, Pr, Nd, and Sm). We reveal that the R substitution is highly effective in gradually introducing a sizable easy-plane magnetocrystalline anisotropy within the Co sublattice. We explain our results in terms of a subtle interplay of structural effects and of indirect interactions between the f and d orbitals from R and Co, respectively. Our observations provide interesting information on the crucial role of R ions in affecting the electronic properties of the CoP layers, of possible interest also for the isostructural FeAs-based family of high-Tc superconductors.