STOICHIOMETRY AND ELECTRONIC-PROPERTIES OF LAMNO3

Treating off-stoichiometric (LaMn)(0.95)O-3 in hydrogen transforms its electrical and magnetic properties. The untreated material is a ferro magnetic narrow-gap semiconductor (T-c = 125 K) whereas the near-stoic hiometric reduced material is an antiferromagnetic insulator T-N = 110 K) Although the off-stoichiometric manganite has formally the same mi xed manganese valency as compounds such as (La0.7Ca0.3)MnO3 there is n o resistivity peak at T-c and no giant magnetoresistance. The differen ce may be due to potential fluctuations associated with cation vacanci es.