ESR-Untersuchungen an antiferromagnetischem CrN zum Einfluß der Temperatur auf die Austausch-Wechselwirkung / ESR-Investigation on Antiferromagnetic CrN Concerning the Influence of Temperature on the Exchange-Interaction

Abstract

Abstract The ESR-behaviour of antiferromagnetic and almost stoechiometric CrN is thoroughly investigated above its Neél-point. For polycrystalline samples a spectroscopic splitting factor g =1.965 and a differential line width ⊿B = 56,7 mT is measured at room temperature. All resonance lines exhibit Lorentzian character to a high degree. In the temperature range between 300 K and 520 K the ESR-intensity can satisfactorily be described by a model of local ordering. Its binding energy is computed to be about ⊿E = 500 ± 20 cm-1. A more refined analysis shows a systematic change of ⊿E with temperature and a discrepancy between the Neel-point TN and the temperature Ts characterizing a singular behaviour of the line width ⊿B. Apart from these deviations originating in a magnetic ordering of the fourth kind, the cluster-model gives an isotropic exchange between next nearest neighbours of J2 = -33.2 cm-1. This result is confirmed by molecular field computations.