EFFECT OF PARTICLE-SIZE ON THE GIANT MAGNETORESISTANCE OF LA0.7CA0.3MNO3

Effect of particle size on the electron transport and magnetic propert ies of La0.7Ca0.3MnO3 has been investigated. While the ferromagnetic T -c, low field magnetic susceptibility, and insulator-metal transition are markedly affected by the particle size, the maximum magnetoresista nce exhibited by the samples near T-c is not sensitive to the particle size. However, the magnetoresistance at 4.2 K increases with decrease in particle size, suggesting a substantial contribution by the grain boundaries. Preliminary measurements on La0.7Sr0.3MnO3 samples of diff erent particle sizes also corroborate the above conclusions. (C) 1996 American Institute of Physics.