Emergence of low-temperature glassy dynamics in Ru substituted non-magnetic insulator CaHfO₃

Abstract

Non–magnetic insulators/semiconductors with induced magnetism introduced via transition metal substitution are one of the promising materials in the field of spintronic, magnetoelectronics and magneto–optical devices. In this context, here, we focus on magnetism induced in a non–magnetic insulator CaHfO3, by the substitution of 4d element Ru, at Hf–site. Structural investigations indicate that substitution of Ru4+ (up to 50%) does not affect the original crystal structure of the parent compound. Magnetic studies divulge a crossover from a diamagnetic to paramagnetic state with 20% Ru substitution. Further replacement of Hf results in a glassy magnetic state in CaHf1-xRuxO3 (0.3 ≤ x ≤ 0.5). The nature of the low temperature glassiness (below 20 K) in these compositions is confirmed through Vogel–Fulcher and Power law, along with, magnetic memory effect and relaxation dynamics. The observed glassiness is explained through the phenomenological “hierarchical model”. Our studies indicate that the presence of competing short range interactions among randomly arranged Ru cations in non–magnetic insulator CaHfO3 are responsible for the observed low temperature magnetic state in this series with compositions > 0.25.