Local Spin Configurations and Magnetic Ordering in Competing-Exchange System (Rh, Pd)90Fe10

Abstract

Mössbauer spectroscopy technique has been used to investigate the evolution of the hyperfine field distributions and the local spin configurations of Fe atoms in the magnetically ordered (Rh1—xPdx)0.9Fe0.1 alloys over the concentration range 0 ≤ x ≤ 1. In the whole composition range, the magnetic behavior of the alloys is governed by the competition between two exchange interactions opposite in sign: the direct antiferromagnetic coupling between the nearest-neighbor Fe atoms and the ferromagnetic interaction due to the matrix polarization. For Rh-rich alloys, this leads to a spin-glass-like magnetic structure, where the ferro- and antiferromagnetic local spin configurations are realized with nearly equal probabilities. For the concentration range x ≤ 0.3, the magnetic ordering temperature is equal to about 32 K independent of the Pd concentration. In the same concentration range, a sharp increase of the magnetic moment of Fe atoms was observed. The severe influence of rhodium on the Curie temperature of the ferromagnetic PdFe alloy is explained by the spin reorientation effect, leading to a destruction of the ferromagnetic spin structure. The strong diffuseness of the magnetic transition in the intermediate concentration range 0.4 < x < 0.8 is due to the presence of Fe sites with both Rh-rich and Pd-rich local environments.