Coexistence of charge ordering and ferromagnetism in Nd0.5Ca0.5Mn1−xCoxO3 (x ≤ 0.1)

Magnetization, resistivity and ultrasonic velocity measurements of the Co-doped manganites Nd0.5Ca0.5Mn1−xCoxO3 (x ≤ 0.1) show several intriguing features: the substitution of Mn by Co partially suppresses the charge-ordered (CO) state and induces a ferromagnetic (FM) and insulator-metal (I-M) transition at low temperature. With increasing Co content, the I-M transition shifts to lower temperature and the depression of ferromagnetism is observed. Ultrasonic velocity anomalies near charge ordering transition temperature Tco, together with magnetization and resistivity data, suggests that the CO state coexists with FM phase at low temperature in these compounds. These phenomena were explained within the phase separation scenario.