Multifrequency electron spin resonance study of the charge-ordered manganite Nd0.5Ca0.5MnO3

Abstract

We performed multifrequency electron spin resonance (ESR) on the antiferromagnetic (TN = 160 K) and charge-ordered (Tco = 250 K) insulating manganite Nd 0 ,Ca05MnO3 . Temperature (4-300 K) and frequency (9.4-285 GHz) dependence of the linewidth, intensity and position of the ESR line were studied. In the paramagnetic state we observe a single Lorentzian absorption line. For a given frequency, the ESR line position is temperature independent (close to g = 1.99). A strong linewidth broadening is observed below Teo . This indicates that there is no magnetic order in the temperature range Tco > T> TN but strong antiferromagnetic fluctuations are present. Below TN , due to high-frequency and high-field ESR (up to 12 T) measurements, we were able to observe unexpected lines within the antiferromagnetic gap revealing the presence of a phase separation.

Phase separation effects in charge-ordered Pr 0.5 Ca 0.5 MnO 3 thin film

“…For the high field, high frequency measurements, the whole film was used (two 2x4mm 2 plates superimposed). For these experiments a homemade spectrometer 11 was used at frequencies of 95 GHz and 190 GHz with a superconducting magnet operating up to 12 Tesla. The magnetic field was kept below the CO/FM transition (6 Tesla for 95 GHz and 8 Tesla for 190 GHz recorded at 150 K) in order to test the phase separation scenario without passing the first order, hysteretic transition.…”