Magnetoresistance and paramagnetic anomalies in La_{(2 -x)/3}Ba_{(1 +x)/3}Mn_{1 -x}Cu_xO₃(x= 0.2)

Abstract

Magnetoresistance (MR) measurements for La(2 - x )/3 Ba(1 + x )/3 Mn1 - x Cux O3(x= 0.2) show that the MR effect becomes observable at Tonset (~ 200 K), sharply increases on further cooling and reaches a maximum at Tc (~ 105 K). Whereas paramagnetic (PM) resonance experiments reveal that PM anomalies occur just below Tonset . Above Tonset , the g -value keeps constant and the resonance linewidth Hpp shows a linear temperature-dependent behaviour, while below Tonset , both the g -value and Hpp anomalously increase on cooling. It is interesting to find that at the range of Tc < T< Tonset , both gand Hpp show temperature-dependent behaviours similar to that for the MR against T . These findings suggest the same underlying physical origin for the MR effect and the PM anomalies.