Detection of structural and magnetic transitions in La0.67Ba0.23Ca0.1MnO3 using the rf resonance technique

We report radio-frequency (rf) electrodynamics in polycrystalline La0.67Ba0.23Ca0.1MnO3 as a function of temperature and magnetic field using a home-built LC resonant circuit powered by an integrated chip oscillator. The resonance frequency (fr) of the oscillator and the power (P) absorbed by the sample are measured simultaneously. The paramagnetic to ferromagnetic phase transition in the absence of an external magnetic field is accompanied by a rapid decrease in both P and fr around the Curie temperature TC=300 K. However, much below TC, the fr shows a step-like anomaly around 165 K (195 K) while cooling (warming), which we attribute to a structural phase transition from high temperature rhombohedral (R3-barc) to low temperature orthorhombic (Imma) phase. The step-like anomaly in fr versus T disappears in a field of 300 G. Fractional changes as large as 19% in Δfr/fr and 10% in ΔP/P are observed under H=1 kG around TC. Our study suggests that the rf resonance technique is a versatile tool to study the magnetization dynamics as well as to investigate the structural phase transition in manganites.