Chakraborty, Amitava and Bhattacharya, Dipten and Maiti, Himadri Sekhar (1997) Zero-field resistivity anomaly and low-field response of the canted antiferromagnetism in unsubstituted and Ba-substituted LaMnO3+delta within the insulating regime. Physical Review B, 56 (14). pp. 8828-8835. ISSN 1098-0121

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Electrical and low-field magnetic properties of unsubstituted LaMnO3+delta and Ba-substituted La1-yBayMnO3+delta systems have been measured over the temperature range 20-300 K. The samples within the insulating regime exhibit rho=rho(o) exp(U/k(B)T) type resistivity (rho) vs temperature (T) pattern (U=activation barrier). However, for the unsubstituted samples with delta=0.031-0.064 and Ba-substituted ones up to a doping level of y=0.05, an anomalous deviation in the rho vs T pattern has been observed below the antiferromagnetic ordering temperature (T-A) which yields a significantly smaller activation barrier in this low-temperature regime. Such an anomaly in rho vs T arises in this temperature regime (when A-type antiferromagnetic spin structure is dominant) possibly due to confinement of charge carriers within the two-dimensional Mn-O planes in a grain. In the case of Ba-substituted samples, the insulator-to-metal transition takes place at a relatively higher doping level (y greater than or equal to 0.2) than what is normally observed in the case of Sr or Ca doping. The insulating samples also exhibit a significant drop in T-A under a low magnetic field (100-5000 Oe). This observation reveals a canted A-type antiferromagnetic structure (rather than a spiral structure) for these samples, as pointed out recently by Kawano ct al.

Item Type: Article
Subjects: Electronics
Depositing User: Bidhan Chaudhuri
Date Deposited: 18 Jul 2012 08:04
Last Modified: 18 Jul 2012 08:04

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