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Changes in the magnetic structure of (La0.25Pr0.75)0.7Ca0.3MnO3 upon the isotopic substitution of 18O for 16O
Authors:A M Balagurov  V Yu Pomyakushin  D V Sheptyakov  V L Aksenov  N A Babushkina  A M Belova  A N Taldenkov  A V Inyushkin  P Fischer  M Gutmann  L Keller  O Yu Gorbenko  V A Amelichev  A R Kaul’
Institution:(1) Neutron Physics Laboratory, Joint Institute of Nuclear Research, 141980 Dubna, Russia;(2) Kurchatov Institute Russian Science Center, 123182 Moscow, Russia;(3) Paul Scherrer Institute, CH-5232 Villigen, Switzerland;(4) Moscow State University, 119899 Moscow, Russia
Abstract:A giant isotope effect, wherein the low-temperature metallic state is replaced by an insulator state, was recently observed when 18O was substituted for 16O in (La0.25Pr0.75)0.7Ca0.3MnO3 N. A. Babushkina, L. M. Belova, O. Yu. Gorbenko et al., Nature (London) 391, 159 (1998)]. In the present work, the temperature evolution of the magnetic structure of two samples of this compound is studied by neutron diffraction. One sample contained a natural mixture of oxygen isotopes, 99.7% 16O, while the other was enriched to 75% with the isotope 18O. It is established that the samples are crystallographically identical at room temperature. As the temperature decreases, the sample with 16O undergoes successive antiferromagnetic (T AFM=5150 K) and ferromagnetic (T FM=110 K) transitions, which lead to the establishment of a noncollinear ferromagnetic structure, while a purely antiferromagnetic (T AFM=150 K) order arises in the sample with 18O. The temperature dependences of the intensities of the diffraction peaks associated with the charge ordering differ substantially in samples with 16O and 18O, and they correlate with the behavior of their electric resistance and magnetic structure. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 46–51 (10 January 1999)
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