Resumo de eventos cient??ficos
Hyperfine field at La in the intermetallic compound LaMnSi2 measured by PAC using 140Ce nuclear probe
Autor
DOMIENIKAN, CLAUDIO
BOSCH-SANTOS, BRIANNA
PASCA, GABRIEL A.C.
SAXENA, RAJENDRA
CARBONARI, ARTUR
INTERNATIONAL CONFERENCE ON HYPERFINE INTERACTIONS AND THEIR APPLICATIONS
Resumen
Magnetic hyperfine field has been measured in the orthorhombic intermetallic compound
LaMnSi2 with PAC spectroscopy using radioactive 140La-140Ce nuclear probes.
Magnetization measurement was also carried out in this compound with MPSM-SQUID
magnetometer. The LaMnSi2 sample was prepared by melting pure metallic components in
stoichiometric proportions in an arc furnace under argon atmosphere. After melting, the
sample was annealed at 1000 o C for 60h under helium atmosphere and then quenched in
to water. X-ray analysis confirmed the sample to be in a single phase with correct crystal
structure expected for LaMnSi2. The radioactive nuclei, 140La (T1/2 = 40h) were produced by
direct irradiation of the sample with neutrons in the IEA-R1 nuclear research reactor at
IPEN with a flux of ~1013 ncm-2s-1 for about 3-4 min. The irradiated sample was annealed
at 1000 o C under helium atmosphere for 24 hours before starting the PAC measurement in
order to minimize the effects of eventual radiation damage by fast neutrons during
irradiation as well as to allow the decay of the short lived 56Mn (T1/2 = 2.6h) activity also
produced in the sample. The PAC measurements were carried out with a six BaF2 detector
spectrometer at several temperatures between 10 K and 400 K. The results showed well
defined magnetic dipole interaction at all temperatures. Temperature dependence of the
hyperfine field, Bhf was found to be anomalous. The magnetization measurement however,
showed no anomaly. Therefore, the anomalous behavior of Bhf may be attributed to the
interaction where 1f electron of the dilute Ce atom is spin polarized by the magnetic field
from Mn sublattice and contributes to the effective hyperfine field. The ferromagnetic
transition temperature (TC) of LaMnSi2 was determined to be 400(1) K confirming by
magnetic measurement and the earlier results.